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															SUPREME COURT OF THE UNITED STATES

															_________________

															No. 11–182

															_________________

															ARIZONA, et al., PETITIONERS v. UNITED STATES

															on writ of certiorari to the united states
court of appeals for the ninth circuit

															[June 25, 2012]

															Justice Kennedy delivered the opinion of the
Court.

															To address pressing issues related to the large
number of aliens within its borders who do not have a lawful right
to be in this country, the State of Arizona in 2010 enacted a
statute called the Support Our Law Enforcement and Safe
Neighborhoods Act. The law is often referred to as S. B. 1070,
the version introduced in the state senate. See also H. 2162 (2010)
(amending S. 1070). Its stated purpose is to “discourage and deter
the unlawful entry and presence of aliens and economic activity by
persons unlawfully present in the United States.” Note following
Ariz. Rev. Stat. Ann. §11–1051 (West 2012). The law’s provisions
establish an official state policy of “attrition through
enforcement.” Ibid. The question before the Court is whether
federal law preempts and renders invalid four separate provisions
of the state law.

															I

															The United States filed this suit against
Arizona, seeking to enjoin S. B. 1070 as preempted. Four provisions
of the law are at issue here. Two create new state offenses.
Section 3 makes failure to comply with federal alien-registration
requirements a state misdemeanor. Ariz. Rev. Stat. Ann. §13–1509
(West Supp. 2011). Section 5, in relevant part, makes it a
misdemeanor for an unauthorized alien to seek or engage in work in
the State; this provision is referred to as §5(C). See §13–2928(C).
Two other provisions give specific arrest authority and inves-
tigative duties with respect to certain aliens to state and local
law enforcement officers. Section 6 authorizes officers to arrest
without a warrant a person “the officer has probable cause to
believe . . . has committed any public offense that makes
the person removable from the United States.” §13–3883(A)(5).
Section 2(B) provides that officers who conduct a stop, detention,
or arrest must in some circumstances make efforts to verify the
person’s immi- gration status with the Federal Government. See
§11–1051(B) (West 2012).

															The United States District Court for the
District of Arizona issued a preliminary injunction preventing the
four provisions at issue from taking effect. 703 F. Supp. 2d 980,
1008 (2010). The Court of Appeals for the Ninth Circuit affirmed.
641 F.3d 339, 366 (2011). It agreed that the United States had
established a likelihood of success on its preemption claims. The
Court of Appeals was unanimous in its conclusion that §§3 and 5(C)
were likely preempted. Judge Bea dissented from the decision to
uphold the preliminary injunction against §§2(B) and 6. This Court
granted certiorari to resolve important questions concerning the
interaction of state and federal power with respect to the law of
immigration and alien status. 565 U. S. ___ (2011).

															II

															A

															The Government of the United States has broad,
undoubted power over the subject of immigration and the status of
aliens. See Toll v. Moreno , 458 U.S.
1 , 10 (1982); see generally S. Legomsky & C. Rodríguez,
Immigration and Refugee Law and Policy 115–132 (5th ed. 2009). This
authority rests, in part, on the National Government’s
constitutional power to “establish an uniform Rule of Nat-
uralization,” U. S. Const., Art. I, §8, cl. 4, and
its inher- ent power as sovereign to control and conduct relations
with foreign nations, see Toll , supra, at 10 (citing United States v. Curtiss-Wright Export Corp. , 299 U.S.
304 , 318 (1936)).

															The federal power to determine immigration
policy is well settled. Immigration policy can affect trade,
investment, tourism, and diplomatic relations for the entire
Nation, as well as the perceptions and expectations of aliens in
this country who seek the full protection of its laws. See, e.g., Brief for Argentina et al. as Amici
Curiae; see also Harisiades v. Shaughnessy , 342 U.S.
580 , 588–589 (1952). Perceived mistreatment of aliens in the
United States may lead to harmful reciprocal treatment of American
citizens abroad. See Brief for Madeleine K. Albright et al. as Amici Curiae 24–30.

															It is fundamental that foreign countries
concerned about the status, safety, and security of their nationals
in the United States must be able to confer and communicate on this
subject with one national sovereign, not the 50 separate States.
See Chy Lung v. Freeman , 92 U.S.
275 , 279–280 (1876); see also The Federalist No. 3, p. 39
(C. Rossiter ed. 2003) (J. Jay) (observing that federal power would
be necessary in part because “bordering States . . .
under the impulse of sudden irritation, and a quick sense of
apparent interest or injury” might take action that would undermine
foreign relations). This Court has reaffirmed that “[o]ne of the
most important and delicate of all international relationships
. . . has to do with the protection of the just rights of
a country’s own nationals when those nationals are in another
country.” Hines v. Davidowitz , 312 U.S.
52 , 64 (1941).

															Federal governance of immigration and alien
status is extensive and complex. Congress has specified catego-
ries of aliens who may not be admitted to the United States. See 8
U. S. C. §1182. Unlawful entry and unlawful reentry into
the country are federal offenses. §§1325, 1326. Once here, aliens
are required to register with the Federal Government and to carry
proof of status on their person. See §§1301–1306. Failure to do so
is a federal misdemeanor. §§1304(e), 1306(a). Federal law also
authorizes States to deny noncitizens a range of public benefits,
§1622; and it imposes sanctions on employers who hire unauthorized
workers, §1324a.

															Congress has specified which aliens may be
removed from the United States and the procedures for doing so.
Aliens may be removed if they were inadmissible at the time of
entry, have been convicted of certain crimes, or meet other
criteria set by federal law. See §1227. Re- moval is a civil, not
criminal, matter. A principal feature of the removal system is the
broad discretion exercised by immigration officials. See Brief for
Former Commissioners of the United States Immigration and
Naturalization Service as Amici Curiae 8–13 (hereinafter
Brief for Former INS Commissioners). Federal officials, as an
initial matter, must decide whether it makes sense to pursue
removal at all. If removal proceedings commence, aliens may seek
asylum and other discretionary relief allowing them to remain in
the country or at least to leave without formal removal. See
§1229a(c)(4); see also, e.g., §§1158 (asylum), 1229b
(cancellation of removal), 1229c (voluntary departure).

															Discretion in the enforcement of immigration law
embraces immediate human concerns. Unauthorized workers trying to
support their families, for example, likely pose less danger than
alien smugglers or aliens who commit a serious crime. The equities
of an individual case may turn on many factors, including whether
the alien has children born in the United States, long ties to the
community, or a record of distinguished military service. Some
discretionary decisions involve policy choices that bear on this
Nation’s international relations. Returning an alien to his own
country may be deemed inappropriate even where he has committed a
removable offense or fails to meet the criteria for admission. The
foreign state may be mired in civil war, complicit in political
persecution, or enduring conditions that create a real risk that
the alien or his family will be harmed upon return. The dynamic
nature of relations with other countries requires the Executive
Branch to ensure that enforcement policies are con- sistent with
this Nation’s foreign policy with respect to these and other
realities.

															Agencies in the Department of Homeland Security
play a major role in enforcing the country’s immigration laws.
United States Customs and Border Protection (CBP) is re- sponsible
for determining the admissibility of aliens and securing the
country’s borders. See Dept. of Homeland Security, Office of
Immigration Statistics, Immigration Enforcement Actions: 2010,
p. 1 (2011). In 2010, CBP’s Border Patrol apprehended almost
half a million people. Id. , at 3. Immigration and Customs
Enforcement (ICE), a second agency, “conducts criminal
investigations involving the enforcement of immigration-related
statutes.” Id. , at 2. ICE also operates the Law Enforcement
Support Center. LESC, as the Center is known, provides immigra-
tion status information to federal, state, and local officials
around the clock. See App. 91. ICE officers are respon- sible “for
the identification, apprehension, and removal of illegal aliens
from the United States.” Immigration Enforcement Actions, supra, at 2. Hundreds of thousands of aliens are removed by
the Federal Government every year. See id., at 4 (reporting
there were 387,242 removals, and 476,405 returns without a removal
order, in 2010).

															B

															The pervasiveness of federal regulation does
not di- minish the importance of immigration policy to the States.
Arizona bears many of the consequences of unlawful immigration.
Hundreds of thousands of deportable aliens are apprehended in
Arizona each year. Dept. of Homeland Security, Office of
Immigration Statistics, 2010 Yearbook of Immigration Statistics 93
(2011) (Table 35). Unauthorized aliens who remain in the State
comprise, by one es- timate, almost six percent of the population.
See Passel & Cohn, Pew Hispanic Center, U. S. Unauthorized
Im- migration Flows Are Down Sharply Since Mid-Decade 3 (2010). And
in the State’s most populous county, these aliens are reported to
be responsible for a disproportionate share of serious crime. See, e.g., Camarota & Vaughan, Center for Immigration
Studies, Immigration and Crime: Assessing a Conflicted Situation 16
(2009) (Table 3) (estimating that unauthorized aliens comprise 8.9%
of the population and are responsible for 21.8% of the felonies in
Maricopa County, which includes Phoenix).

															Statistics alone do not capture the full extent
of Arizona’s concerns. Accounts in the record suggest there is an
“epidemic of crime, safety risks, serious property damage, and
environmental problems” associated with the influx of illegal
migration across private land near the Mexican border. Brief for
Petitioners 6. Phoenix is a major city of the United States, yet
signs along an interstate highway 30 miles to the south warn the
public to stay away. One reads, “DANGER—PUBLIC WARNING—TRAVEL NOT
RECOMMENDED / Active Drug and Human Smuggling Area / Visitors May
Encounter Armed Criminals and Smuggling Vehicles Traveling at High
Rates of Speed.” App. 170; see also Brief for Petitioners 5–6. The
problems posed to the State by illegal immigration must not be
underestimated.

															These concerns are the background for the formal
legal analysis that follows. The issue is whether, under pre-
emption principles, federal law permits Arizona to implement the
state-law provisions in dispute.

															III

															Federalism, central to the constitutional
design, adopts the principle that both the National and State
Governments have elements of sovereignty the other is bound to
respect. See Gregory v. Ashcroft , 501 U.S.
452 , 457 (1991); U. S. Term Limits, Inc. v. Thornton , 514 U.S.
779 , 838 (1995) (Kennedy, J., concurring). From the existence
of two sovereigns follows the possibility that laws can be in
conflict or at cross-purposes. The Supremacy Clause provides a
clear rule that federal law “shall be the supreme Law of the Land;
and the Judges in every State shall be bound thereby, any Thing in
the Constitution or Laws of any State to the Contrary
notwithstanding.” Art. VI, cl. 2. Under this principle,
Congress has the power to preempt state law. See Crosby v. National Foreign Trade Council , 530
U.S. 363 , 372 (2000); Gibbons v. Ogden , 9 Wheat.
1, 210–211 (1824). There is no doubt that Congress may withdraw
specified powers from the States by enacting a statute containing
an express preemption provision. See, e.g., Chamber of
Commerce of United States of America v. Whiting , 563
U. S. ___, ___ (2011) (slip op., at 4).

															State law must also give way to federal law in
at least two other circumstances. First, the States are precluded
from regulating conduct in a field that Congress, acting within its
proper authority, has determined must be regulated by its exclusive
governance. See Gade v. National Solid Wastes Management
Assn., 505 U.S.
88 , 115 (1992). The intent to displace state law altogether can
be inferred from a framework of regulation “so pervasive
. . . that Congress left no room for the States to
supplement it” or where there is a “federal interest
. . . so dominant that the federal system will be assumed
to preclude enforcement of state laws on the same subject.” Rice v. Santa Fe Elevator Corp. , 331 U.S.
218 , 230 (1947); see English v. General Elec.
Co. , 496 U.S.
72 , 79 (1990).

															Second, state laws are preempted when they
conflict with federal law. Crosby, supra, at 372. This
includes cases where “compliance with both federal and state
regulations is a physical impossibility,” Florida Lime &
Avocado Growers, Inc. v. Paul , 373
U.S. 132 , 142–143 (1963), and those instances where the
challenged state law “stands as an obstacle to the accomplishment
and execution of the full purposes and objectives of Congress,” Hines , 312 U. S., at 67; see also Crosby , supra , at 373 (“What is a sufficient obstacle is a matter of
judgment, to be informed by examining the federal statute as a
whole and identifying its purpose and intended effects”). In
preemption analysis, courts should assume that “the historic police
powers of the States” are not superseded “unless that was the clear
and manifest purpose of Congress.” Rice , supra, at
230; see Wyeth v. Levine , 555
U.S. 555 , 565 (2009).

															The four challenged provisions of the state law
each must be examined under these preemption principles.

															IV

															A Section 3 Section 3 of S. B. 1070 creates a new state
misde- meanor. It forbids the “willful failure to complete or carry
an alien registration document . . . in violation of 8
United States Code section 1304(e) or 1306(a).” Ariz. Rev. Stat.
Ann. §11–1509(A) (West Supp. 2011). In effect, §3 adds a state-law
penalty for conduct proscribed by federal law. The United States
contends that this state enforcement mechanism intrudes on the
field of alien registration, a field in which Congress has left no
room for States to regulate. See Brief for United States 27,
31.

															The Court discussed federal alien-registration
requirements in Hines v. Davidowitz , 312 U.S.
52 . In 1940, as international conflict spread, Congress added
to federal immigration law a “complete system for alien
registration.” Id. , at 70. The new federal law struck a
careful balance. It punished an alien’s willful failure to register
but did not require aliens to carry identification cards. There
were also limits on the sharing of registration records and
fingerprints. The Court found that Congress intended the federal
plan for registration to be a “single integrated and all-embracing
system.” Id. , at 74. Because this “complete scheme
. . . for the registration of aliens” touched on foreign
relations, it did not allow the States to “curtail or complement”
federal law or to “enforce additional or auxiliary regulations.” Id. , at 66–67. As a con- sequence, the Court ruled that
Pennsylvania could not enforce its own alien-registration program.
See id. , at 59, 74.

															The present regime of federal regulation is not
identi- cal to the statutory framework considered in Hines ,
but it remains comprehensive. Federal law now includes a
requirement that aliens carry proof of registration. 8
U. S. C. §1304(e). Other aspects, however, have stayed
the same. Aliens who remain in the country for more than 30 days
must apply for registration and be fingerprinted. Compare §1302(a)
with id. , §452(a) (1940 ed.). Detailed information is
required, and any change of address has to be reported to the
Federal Government. Compare §§1304(a), 1305(a) (2006 ed.), with id. , §§455(a), 456 (1940 ed.). The statute continues to
provide penalties for the willful failure to register. Compare
§1306(a) (2006 ed.), with id. , §457 (1940 ed.).

															The framework enacted by Congress leads to the
conclusion here, as it did in Hines , that the Federal
Government has occupied the field of alien registration. See American Ins. Assn. v. Garamendi , 539 U.S.
396 , 419, n. 11 (2003) (characterizing Hines as a
field preemption case); Pennsylvania v. Nelson , 350 U.S.
497 , 504 (1956) (same); see also Dinh, Reassessing the Law of
Preemption, 88 Geo. L. J. 2085, 2098–2099, 2107 (2000) (same).
The federal statu- tory directives provide a full set of standards
governing alien registration, including the punishment for
noncompliance. It was designed as a “ ‘harmonious
whole.’ ” Hines , supra, at 72. Where Congress
occupies an entire field, as it has in the field of alien
registration, even complementary state regulation is impermissible.
Field pre- emption reflects a congressional decision to foreclose
any state regulation in the area, even if it is parallel to fed-
eral standards. See Silkwood v. Kerr-McGee Corp. , 464 U.S.
238 , 249 (1984).

															Federal law makes a single sovereign responsible
for maintaining a comprehensive and unified system to keep track of
aliens within the Nation’s borders. If §3 of the Arizona statute
were valid, every State could give itself independent authority to
prosecute federal registration violations, “diminish[ing] the
[Federal Government]’s control over enforcement” and “detract[ing]
from the ‘integrated scheme of regulation’ created by Congress.” Wisconsin Dept. of Industry v. Gould Inc. , 475 U.S.
282 , 288–289 (1986). Even if a State may make violation of
federal law a crime in some instances, it cannot do so in a field
(like the field of alien registration) that has been occupied by
federal law. See California v. Zook , 336 U.S.
725 , 730–731, 733 (1949); see also In re Loney , 134 U.S.
372 , 375–376 (1890) (States may not impose their own punishment
for perjury in federal courts).

															Arizona contends that §3 can survive preemption
because the provision has the same aim as federal law and adopts
its substantive standards. This argument not only ignores the basic
premise of field preemption—that States may not enter, in any
respect, an area the Federal Government has reserved for itself—but
also is unpersuasive on its own terms. Permitting the State to
impose its own penalties for the federal offenses here would
conflict with the careful framework Congress adopted. Cf. Buckman Co. v. Plaintiffs’ Legal Comm. , 531 U.S.
341 , 347–348 (2001) (States may not impose their own punishment
for fraud on the Food and Drug Administration); Wisconsin Dept.,
supra, at 288 (States may not impose their own punishment for
repeat violations of the National Labor Relations Act). Were §3 to
come into force, the State would have the power to bring criminal
charges against individuals for violating a federal law even in
circumstances where federal officials in charge of the
comprehensive scheme determine that prosecution would frustrate
federal policies.

															There is a further intrusion upon the federal
scheme. Even where federal authorities believe prosecution is ap-
propriate, there is an inconsistency between §3 and fed- eral law
with respect to penalties. Under federal law, the failure to carry
registration papers is a misdemeanor that may be punished by a
fine, imprisonment, or a term of probation. See 8
U. S. C. §1304(e) (2006 ed.); 18 U. S. C.
§3561. State law, by contrast, rules out probation as a possible
sentence (and also eliminates the possibility of a pardon). See
Ariz. Rev. Stat. Ann. §13–1509(D) (West Supp. 2011). This state
framework of sanctions creates a conflict with the plan Congress
put in place. See Wisconsin Dept. , supra, at 286
(“[C]onflict is imminent whenever two separate remedies are brought
to bear on the same activity” (internal quotation marks
omitted)).

															These specific conflicts between state and
federal law simply underscore the reason for field preemption. As
it did in Hines , the Court now concludes that, with respect
to the subject of alien registration, Congress intended to preclude
States from “complement[ing] the federal law, or enforc[ing]
additional or auxiliary regulations.” 312 U. S., at 66–67.
Section 3 is preempted by federal law.

															B Section 5(C) Unlike §3, which replicates federal statutory
requirements, §5(C) enacts a state criminal prohibition where no
federal counterpart exists. The provision makes it a state
misdemeanor for “an unauthorized alien to knowingly ap- ply for
work, solicit work in a public place or perform work as an employee
or independent contractor” in Ari- zona. Ariz. Rev. Stat. Ann.
§13–2928(C) (West Supp. 2011). Violations can be punished by a
$2,500 fine and incarceration for up to six months. See
§13–2928(F); see also §§13–707(A)(1) (West 2010); 13–802(A);
13–902(A)(5). The United States contends that the provision upsets
the bal- ance struck by the Immigration Reform and Control Act of
1986 (IRCA) and must be preempted as an obstacle to the federal
plan of regulation and control.

															When there was no comprehensive federal program
regulating the employment of unauthorized aliens, this Court found
that a State had authority to pass its own laws on the subject. In
1971, for example, California passed a law imposing civil penalties
on the employment of aliens who were “not entitled to lawful
residence in the United States if such employment would have an
adverse effect on lawful resident workers.” 1971 Cal. Stats. ch.
1442, §1(a). The law was upheld against a preemption challenge in De Canas v. Bica , 424 U.S.
351 (1976). De Canas recognized that “States possess
broad authority under their police powers to regulate the
employment relationship to protect workers within the State.” Id., at 356. At that point, however, the Federal Government
had expressed no more than “a peripheral concern with [the]
employment of illegal entrants.” Id. , at 360; see Whiting , 563 U. S., at ___ (slip op., at 3).

															Current federal law is substantially different
from the regime that prevailed when De Canas was decided.
Congress enacted IRCA as a comprehensive framework for “combating
the employment of illegal aliens.” Hoffman Plastic Compounds,
Inc. v. NLRB , 535 U.S.
137 , 147 (2002). The law makes it illegal for employers to
know- ingly hire, recruit, refer, or continue to employ
unauthorized workers. See 8 U. S. C. §§1324a(a)(1)(A),
(a)(2). It also requires every employer to verify the employment
authorization status of prospective employees. See §§1324a(a)
(1)(B), (b); 8 CFR §274a.2(b) (2012). These requirements are
enforced through criminal penalties and an escalat- ing series of
civil penalties tied to the number of times an employer has
violated the provisions. See 8 U. S. C. §§1324a(e)(4),
(f); 8 CFR §274 A. 10.

															This comprehensive framework does not impose
federal criminal sanctions on the employee side ( i.e., penalties on aliens who seek or engage in unauthorized work). Under
federal law some civil penalties are imposed instead. With certain
exceptions, aliens who accept unlawful employment are not eligible
to have their status adjusted to that of a lawful permanent
resident. See 8 U. S. C. §§1255(c)(2), (c)(8). Aliens
also may be removed from the country for having engaged in
unauthorized work. See §1227(a)(1)(C)(i); 8 CFR §214.1(e). In
addition to specifying these civil consequences, federal law makes
it a crime for unauthorized workers to obtain employment through
fraudulent means. See 18 U. S. C. §1546(b). Congress has
made clear, however, that any information employees submit to
indicate their work status “may not be used” for purposes other
than prosecution under specified federal criminal statutes for
fraud, perjury, and related conduct. See 8 U. S. C.
§§1324a(b)(5), (d)(2)(F)–(G).

															The legislative background of IRCA underscores
the fact that Congress made a deliberate choice not to impose crim-
inal penalties on aliens who seek, or engage in, unauthorized
employment. A commission established by Congress to study
immigration policy and to make recommen- dations concluded these
penalties would be “unnecessary and unworkable.” U. S.
Immigration Policy and the National Interest: The Final Report and
Recommendations of the Select Commission on Immigration and Refugee
Policy with Supplemental Views by Commissioners 65–66 (1981); see
Pub. L. 95–412, §4, 92Stat. 907. Proposals to make unauthorized
work a criminal offense were debated and discussed during the long
process of drafting IRCA. See Brief for Service Employees
International Union et al. as Amici Curiae 9–12. But
Congress rejected them. See, e.g., 119 Cong. Rec. 14184
(1973) (statement of Rep. Dennis). In the end, IRCA’s framework
reflects a considered judgment that making criminals out of aliens
engaged in unauthorized work—aliens who already face the
possibility of employer exploitation because of their removable
status—would be inconsistent with federal policy and ob- jectives.
See, e.g., Hearings before the Subcommittee No. 1 of
the House Committee on the Judiciary, 92d Cong., 1st Sess.,
pt. 3, pp. 919–920 (1971) (statement of Rep. Rodino, the
eventual sponsor of IRCA in the House of Representatives).

															IRCA’s express preemption provision, which in
most instances bars States from imposing penalties on employers of
unauthorized aliens, is silent about whether additional penalties
may be imposed against the employees themselves. See 8
U. S. C. §1324a(h)(2); Whiting, supra, at ___–___
(slip op., at 1–2). But the existence of an “express pre-emption
provisio[n] does not bar the ordinary working of conflict
pre-emption principles” or impose a “special burden” that would
make it more difficult to establish the preemption of laws falling
outside the clause. Geier v. American Honda Motor
Co. , 529 U.S.
861 , 869–872 (2000); see Sprietsma v. Mercury
Marine , 537 U.S.
51 , 65 (2002).

															The ordinary principles of preemption include
the well-settled proposition that a state law is preempted where it
“stands as an obstacle to the accomplishment and exe- cution of the
full purposes and objectives of Congress.” Hines , 312
U. S., at 67. Under §5(C) of S. B. 1070, Arizona law would
interfere with the careful balance struck by Congress with respect
to unauthorized employment of aliens. Although §5(C) attempts to
achieve one of the same goals as federal law—the deterrence of
unlawful employment—it involves a conflict in the method of
enforcement. The Court has recognized that a “[c]onflict in
technique can be fully as disruptive to the system Congress enacted
as conflict in overt policy.” Motor Coach Employees v. Lockridge , 403 U.S.
274 , 287 (1971). The correct instruction to draw from the text,
structure, and history of IRCA is that Congress decided it would be
inappropriate to impose criminal penalties on aliens who seek or
engage in unauthorized employment. It follows that a state law to
the contrary is an obstacle to the regulatory system Congress
chose. See Puerto Rico Dept. of Con- sumer Affairs v. ISLA Petroleum Corp. , 485 U.S.
495 , 503 (1988) (“Where a comprehensive federal scheme
intentionally leaves a portion of the regulated field without
controls, then the pre-emptive inference can be drawn—not
from federal inaction alone, but from inaction joined with
action”). Section 5(C) is preempted by federal law.

															C Section 6 Section 6 of S. B. 1070 provides that a state
officer, “without a warrant, may arrest a person if the officer has
probable cause to believe . . . [the person] has
committed any public offense that makes [him] removable from the
United States.” Ariz. Rev. Stat. Ann. §13–3883(A)(5) (West Supp.
2011). The United States argues that arrests authorized by this
statute would be an obstacle to the removal system Congress
created.

															As a general rule, it is not a crime for a
removable alien to remain present in the United States. See INS v. Lopez-Mendoza , 468 U.S.
1032 , 1038 (1984). If the police stop someone based on nothing
more than possible removability, the usual predicate for an arrest
is absent. When an alien is suspected of being removable, a federal
official issues an administrative document called a Notice to Ap-
pear. See 8 U. S. C. §1229(a); 8 CFR §239.1(a) (2012).
The form does not authorize an arrest. Instead, it gives the alien
information about the proceedings, including the time and date of
the removal hearing. See 8 U. S. C. §1229(a)(1). If an
alien fails to appear, an in absentia order may direct
removal. §1229a(5)(A).

															The federal statutory structure instructs when
it is ap- propriate to arrest an alien during the removal process.
For example, the Attorney General can exercise discretion to issue
a warrant for an alien’s arrest and detention “pending a decision
on whether the alien is to be removed from the United States.” 8
U. S. C. §1226(a); see Memorandum from John Morton,
Director, ICE, to All Field Office Directors et al., Exercising
Prosecutorial Discretion Consistent with the Civil Immigration
Enforcement Priorities of the Agency for the Apprehension,
Detention, and Removal of Aliens (June 17, 2011) (hereinafter 2011
ICE Memorandum) (describing factors informing this and re- lated
decisions). And if an alien is ordered removed after a hearing, the
Attorney General will issue a warrant. See 8 CFR §241.2(a)(1). In
both instances, the warrants are executed by federal officers who
have received training in the enforcement of immigration law. See
§§241.2(b), 287.5(e)(3). If no federal warrant has been issued,
those officers have more limited authority. See 8
U. S. C. §1357(a). They may arrest an alien for being “in
the United States in violation of any [immigration] law or regula-
tion,” for example, but only where the alien “is likely to escape
before a warrant can be obtained.” §1357(a)(2).

															Section 6 attempts to provide state officers
even greater authority to arrest aliens on the basis of possible
removability than Congress has given to trained federal immi-
gration officers. Under state law, officers who believe an alien is
removable by reason of some “public offense” would have the power
to conduct an arrest on that basis regardless of whether a federal
warrant has issued or the alien is likely to escape. This state
authority could be exercised without any input from the Federal
Government about whether an arrest is warranted in a particular
case. This would allow the State to achieve its own immigra- tion
policy. The result could be unnecessary harassment of some aliens
(for instance, a veteran, college student, or someone assisting
with a criminal investigation) whom federal officials determine
should not be removed.

															This is not the system Congress created. Federal
law specifies limited circumstances in which state officers may
perform the functions of an immigration officer. A principal
example is when the Attorney General has granted that authority to
specific officers in a formal agreement with a state or local
government. See §1357(g)(1); see also §1103(a)(10) (authority may
be extended in the event of an “imminent mass influx of aliens off
the coast of the United States”); §1252c (authority to arrest in
specific circumstance after consultation with the Federal
Government); §1324(c) (authority to arrest for bringing in and
harboring certain aliens). Officers covered by these agreements are
subject to the Attorney General’s direction and super- vision.
§1357(g)(3). There are significant complexities involved in
enforcing federal immigration law, including the determination
whether a person is removable. See Padilla v. Kentucky , 559 U. S. ___, ___–___ (2010) (Alito, J.,
concurring in judgment) (slip op., at 4–7). As a result, the
agreements reached with the Attorney General must contain written
certification that officers have received adequate training to
carry out the duties of an immigration officer. See §1357(g)(2);
cf. 8 CFR §§287.5(c) (ar- rest power contingent on training),
287.1(g) (defining the training).

															By authorizing state officers to decide whether
an alien should be detained for being removable, §6 violates the
principle that the removal process is entrusted to the discretion
of the Federal Government. See, e.g., Reno v. American-Arab Anti-Discrimination Comm., 525 U.S.
471 , 483–484 (1999); see also Brief for Former INS
Commissioners 8–13. A decision on removability requires a
determination whether it is appropriate to allow a foreign national
to continue living in the United States. Decisions of this nature
touch on foreign relations and must be made with one voice. See Jama v. Immigration and Customs Enforcement , 543 U.S.
335 , 348 (2005) (“Removal decisions, including the selection of
a removed alien’s destination, may implicate [the Nation’s]
relations with foreign powers and require consideration of changing
political and economic circumstances” (internal quotation marks
omitted)); see also Galvan v. Press , 347 U.S.
522 , 531 (1954) (“Policies pertaining to the entry of aliens
and their right to remain here are . . . entrusted
exclusively to Congress . . .”); Truax v. Raich , 239 U.S.
33 , 42 (1915) (“The authority to control immigration—to admit
or exclude aliens—is vested solely in the Federal Government”).

															In defense of §6, Arizona notes a federal
statute permitting state officers to “cooperate with the Attorney
General in the identification, apprehension, detention, or removal
of aliens not lawfully present in the United States.” 8
U. S. C. §1357(g)(10)(B). There may be some ambiguity as
to what constitutes cooperation under the federal law; but no
coherent understanding of the term would incorporate the unilateral
decision of state officers to arrest an alien for being removable
absent any request, approval, or other instruction from the Federal
Government. The Department of Homeland Security gives examples of
what would constitute cooperation under federal law. These include
situations where States participate in a joint task force with
federal officers, provide operational support in executing a
warrant, or allow federal immigration officials to gain access to
detainees held in state facilities. See Dept. of Homeland Security,
Guidance on State and Local Governments’ Assistance in Immigration
Enforcement and Related Matters 13–14 (2011), online at http://
www.dhs.gov/files/resources/immigration.shtm (all Internet
materials as visited June 21, 2012, and available in Clerk of
Court’s case file). State officials can also assist the Federal
Government by responding to requests for information about when an
alien will be released from their custody. See §1357(d). But the
unilateral state action to detain authorized by §6 goes far beyond
these measures, defeating any need for real cooperation.

															Congress has put in place a system in which
state officers may not make warrantless arrests of aliens based on
possible removability except in specific, limited circumstances. By
nonetheless authorizing state and local offi- cers to engage in
these enforcement activities as a general matter, §6 creates an
obstacle to the full purposes and objectives of Congress. See Hines , 312 U. S., at 67. Section 6 is preempted by
federal law.

															D Section 2(B) Section 2(B) of S. B. 1070 requires state
officers to make a “reasonable attempt . . . to determine
the immigration status” of any person they stop, detain, or arrest
on some other legitimate basis if “reasonable suspicion exists that
the person is an alien and is unlawfully present in the United
States.” Ariz. Rev. Stat. Ann. §11–1051(B) (West 2012). The law
also provides that “[a]ny person who is arrested shall have the
person’s immigration status determined before the person is
released.” Ibid. The accepted way to perform these status
checks is to contact ICE, which maintains a database of immigration
records.

															Three limits are built into the state provision.
First, a detainee is presumed not to be an alien unlawfully present
in the United States if he or she provides a valid Arizona driver’s
license or similar identification. Second, officers “may not
consider race, color or national origin . . . except to
the extent permitted by the United States [and] Ari- zona
Constitution[s].” Ibid. Third, the provisions must be
“implemented in a manner consistent with federal law regulating
immigration, protecting the civil rights of all persons and
respecting the privileges and immunities of United States
citizens.” §11–1051(L) (West 2012).

															The United States and its amici contend
that, even with these limits, the State’s verification requirements
pose an obstacle to the framework Congress put in place. The first
concern is the mandatory nature of the status checks. The second is
the possibility of prolonged detention while the checks are being
performed.

															1

															Consultation between federal and state
officials is an important feature of the immigration system.
Congress has made clear that no formal agreement or special
training needs to be in place for state officers to “communicate
with the [Federal Government] regarding the immigration status of
any individual, including reporting knowledge that a particular
alien is not lawfully present in the United States.” 8
U. S. C. §1357(g)(10)(A). And Congress has obligated ICE
to respond to any request made by state officials for verification
of a person’s citizenship or im- migration status. See §1373(c);
see also §1226(d)(1)(A) (requiring a system for determining whether
individuals arrested for aggravated felonies are aliens). ICE’s Law
Enforcement Support Center operates “24 hours a day, seven days a
week, 365 days a year” and provides, among other things,
“immigration status, identity information and real-time assistance
to local, state and federal law enforcement agencies.” ICE, Fact
Sheet: Law Enforcement Support Center (May 29, 2012), online at
http:// www.ice.gov/news/library/factsheets/lesc.htm. LESC
responded to more than one million requests for information in 2009
alone. App. 93.

															The United States argues that making status
verification mandatory interferes with the federal immigration
scheme. It is true that §2(B) does not allow state officers to
consider federal enforcement priorities in deciding whether to
contact ICE about someone they have detained. See Brief for United
States 47–50. In other words, the officers must make an inquiry
even in cases where it seems unlikely that the Attorney General
would have the alien removed. This might be the case, for example,
when an alien is an elderly veteran with significant and
longstanding ties to the community. See 2011 ICE Memorandum 4–5
(mentioning these factors as relevant).

															Congress has done nothing to suggest it is
inappropriate to communicate with ICE in these situations, however.
Indeed, it has encouraged the sharing of information about possible
immigration violations. See 8 U. S. C. §1357(g) (10)(A).
A federal statute regulating the public benefits provided to
qualified aliens in fact instructs that “no State or local
government entity may be prohibited, or in any way restricted, from
sending to or receiving from [ICE] information regarding the
immigration status, lawful or unlawful, of an alien in the United
States.” §1644. The federal scheme thus leaves room for a policy
requiring state officials to contact ICE as a routine matter. Cf. Whiting , 563 U. S., at ___–___ (slip op., at 23–24)
(rejecting argument that federal law preempted Arizona’s
requirement that employers determine whether employees were
eligible to work through the federal E-Verify system where the
Federal Government had encouraged its use).

															2

															Some who support the challenge to §2(B) argue
that, in practice, state officers will be required to delay the
release of some detainees for no reason other than to verify their
immigration status. See, e.g., Brief for Former Arizona
Attorney General Terry Goddard et al. as Amici Curiae 37, n. 49. Detaining individuals solely to verify their
immigration status would raise constitutional concerns. See, e.g. , Arizona v. Johnson , 555 U.S.
323 , 333 (2009); Illinois v. Caballes , 543 U.S.
405 , 407 (2005) (“A seizure that is justified solely by the
interest in issuing a warning ticket to the driver can become
unlawful if it is prolonged beyond the time reasonably required to
complete that mission”). And it would disrupt the federal framework
to put state officers in the position of holding aliens in custody
for possible unlawful presence without federal direction and
supervision. Cf. Part IV–C, supra (concluding that Ari- zona
may not authorize warrantless arrests on the basis of
removability). The program put in place by Congress does not allow
state or local officers to adopt this enforcement mechanism.

															But §2(B) could be read to avoid these concerns.
To take one example, a person might be stopped for jaywalking in
Tucson and be unable to produce identification. The first sentence
of §2(B) instructs officers to make a “reasonable” attempt to
verify his immigration status with ICE if there is reasonable
suspicion that his presence in the United States is unlawful. The
state courts may conclude that, unless the person continues to be
suspected of some crime for which he may be detained by state
officers, it would not be reasonable to prolong the stop for the
immigration inquiry. See Reply Brief for Petitioners 12, n. 4
(“[Section 2(B)] does not require the verification be completed
during the stop or detention if that is not reasonable or
practicable”); cf. Muehler v. Mena , 544 U.S.
93 , 101 (2005) (finding no Fourth Amendment violation where
questioning about immigration status did not prolong a stop).

															To take another example, a person might be held
pending release on a charge of driving under the influence of
alcohol. As this goes beyond a mere stop, the arrestee (unlike the
jaywalker) would appear to be subject to the categorical
requirement in the second sentence of §2(B) that “[a]ny person who
is arrested shall have the person’s immigration status determined
before [he] is released.” State courts may read this as an
instruction to initiate a status check every time someone is
arrested, or in some subset of those cases, rather than as a
command to hold the person until the check is complete no matter
the circumstances. Even if the law is read as an instruction to
complete a check while the person is in custody, moreover, it is
not clear at this stage and on this record that the verification
process would result in prolonged detention. However the law is
interpreted, if §2(B) only requires state officers to conduct a
status check during the course of an authorized, lawful detention
or after a detainee has been released, the provision likely would
survive pre- emption—at least absent some showing that it has other
consequences that are adverse to federal law and its objectives.
There is no need in this case to address whether reasonable
suspicion of illegal entry or another immigration crime would be a
legitimate basis for prolonging a detention, or whether this too
would be preempted by federal law. See, e.g., United States v. Di Re , 332 U.S.
581 , 589 (1948) (authority of state officers to make arrests
for federal crimes is, absent federal statutory instruction, a
matter of state law); Gonzales v. Peoria , 722 F.2d
468, 475–476 (CA9 1983) (concluding that Arizona officers have
authority to enforce the criminal provisions of federal immigration
law), overruled on other grounds in Hodgers-Durgin v. de
la Vina , 199 F.3d 1037 (CA9 1999).

															The nature and timing of this case counsel
caution in evaluating the validity of §2(B). The Federal Government
has brought suit against a sovereign State to challenge the
provision even before the law has gone into effect. There is a
basic uncertainty about what the law means and how it will be
enforced. At this stage, without the benefit of a definitive
interpretation from the state courts, it would be inappropriate to
assume §2(B) will be construed in a way that creates a conflict
with federal law. Cf. Fox v. Washington , 236 U.S.
273 , 277 (1915) (“So far as statutes fairly may be construed in
such a way as to avoid doubtful constitutional questions they
should be so construed; and it is to be presumed that state laws
will be construed in that way by the state courts” (citation
omitted)). As a result, the United States cannot prevail in its
current challenge. See Huron Portland Cement Co. v. Detroit , 362 U.S.
440 , 446 (1960) (“To hold otherwise would be to ignore the
teaching of this Court’s decisions which enjoin seeking out
conflicts between state and federal regulation where none clearly
exists”). This opinion does not foreclose other preemption and
constitutional challenges to the law as interpreted and applied
after it goes into effect.

															V

															Immigration policy shapes the destiny of the
Nation. On May 24, 2012, at one of this Nation’s most distinguished
museums of history, a dozen immigrants stood before the tattered
flag that inspired Francis Scott Key to write the National Anthem.
There they took the oath to become American citizens. The
Smithsonian, News Release, Smithsonian Citizenship Ceremony
Welcomes a Dozen New Americans (May 24, 2012), online at
http://newsdesk.si.edu/releases. These naturalization cere- monies
bring together men and women of different ori- gins who now share a
common destiny. They swear a common oath to renounce fidelity to
foreign princes, to defend the Constitution, and to bear arms on
behalf of the country when required by law. 8 CFR §337.1(a) (2012).
The history of the United States is in part made of the stories,
talents, and lasting contributions of those who crossed oceans and
deserts to come here.

															The National Government has significant power to
regulate immigration. With power comes responsibility, and the
sound exercise of national power over immigration depends on the
Nation’s meeting its responsibility to base its laws on a political
will informed by searching, thoughtful, rational civic discourse.
Arizona may have understandable frustrations with the problems
caused by illegal immigration while that process continues, but the
State may not pursue policies that undermine federal law.

															*  *  *

															The United States has established that §§3,
5(C), and 6 of S. B. 1070 are preempted. It was improper, however,
to enjoin §2(B) before the state courts had an opportunity to
construe it and without some showing that enforcement of the
provision in fact conflicts with federal immigration law and its
objectives.

															The judgment of the Court of Appeals for the
Ninth Circuit is affirmed in part and reversed in part. The case is
remanded for further proceedings consistent with this opinion.

															It is so ordered.

															Justice Kagan took no part in the consideration
or decision of this case. SUPREME COURT OF THE UNITED STATES

															_________________

															No. 11–182

															_________________

															ARIZONA, et al., PETITIONERS v. UNITED STATES

															on writ of certiorari to the united states
court of appeals for the ninth circuit

															[June 25, 2012]

															Justice Scalia, concurring in part and
dissenting in part.

															The United States is an indivisible “Union of
sovereign States.” Hinderlider v. La Plata River &
Cherry Creek Ditch Co. , 304 U.S.
92 , 104 (1938). Today’s opinion, approving virtually all of the
Ninth Circuit’s injunction against enforcement of the four
challenged provisions of Arizona’s law, deprives States of what
most would con- sider the defining characteristic of sovereignty:
the power to exclude from the sovereign’s territory people who have
no right to be there. Neither the Constitution itself nor even any
law passed by Congress supports this result. I dissent.

															I

															As a sovereign, Arizona has the inherent power
to exclude persons from its territory, subject only to those
limitations expressed in the Constitution or constitution- ally
imposed by Congress. That power to exclude has long been recognized
as inherent in sovereignty. Emer de Vattel’s seminal 1758 treatise
on the Law of Nations stated:

															“The sovereign may forbid the entrance of
his territory either to foreigners in general, or in particular
cases, or to certain persons, or for certain particular pur- poses,
according as he may think it advantageous to the state. There is
nothing in all this, that does not flow from the rights of domain
and sovereignty: every one is obliged to pay respect to the
prohibition; and whoever dares violate it, incurs the penalty
decreed to render it effectual.” The Law of Nations, bk. II, ch.
VII, §94, p. 309 (B. Kapossy & R. Whatmore eds. 2008).

															See also I R. Phillimore, Commentaries upon
International Law, pt. III, ch. X, p. 233 (1854) (“It is a received
maxim of International Law that, the Government of a State may
prohibit the entrance of strangers into the country”).[ 1 ]

															There is no doubt that “before the adoption of
the constitution of the United States” each State had the author-
ity to “prevent [itself] from being burdened by an influx of
persons.” Mayor of New York v. Miln , 11 Pet. 102,
132–133 (1837). And the Constitution did not strip the States of
that authority. To the contrary, two of the Constitution’s
provisions were designed to enable the States to prevent “the
intrusion of obnoxious aliens through other States.” Letter from
James Madison to Edmund Randolph (Aug. 27, 1782), in 1 The Writings
of James Madison 226 (1900); accord, The Federalist No. 42, pp.
269–271 (C. Rossiter ed. 1961) (J. Madison). The Articles of
Confederation had provided that “the free inhabitants of each of
these States, paupers, vagabonds and fugitives from justice
excepted, shall be entitled to all privileges and immunities of
free citizens in the several States.” Articles of Confederation,
Art. IV. This meant that an unwelcome alien could obtain all the
rights of a citizen of one State simply by first becoming an inhabitant of another. To remedy this, the Constitution’s
Privileges and Immunities Clause provided that “[t]he Citizens of each State shall be entitled to all Privileges
and Immunities of Citizens in the several States.” Art. IV, §2,
cl. 1 (emphasis added). But if one State had particularly lax
citizenship standards, it might still serve as a gateway for the
entry of “obnoxious aliens” into other States. This problem was
solved “by authorizing the general government to establish a
uniform rule of naturalization throughout the United States.” The
Federalist No. 42, supra, at 271; see Art. I, §8,
cl. 4. In other words, the naturalization power was given to
Congress not to abrogate States’ power to exclude those they did
not want, but to vindicate it.

															Two other provisions of the Constitution are an
acknowledgment of the States’ sovereign interest in protecting
their borders. Article I provides that “[n]o State shall, without
the Consent of the Congress, lay any Imposts or Duties on Imports
or Exports, except what may be absolutely necessary for
executing it’s inspection Laws .” Art. I, §10, cl. 2
(emphasis added). This assumed what everyone assumed: that the
States could exclude from their territory dangerous or unwholesome
goods. A later portion of the same section provides that “[n]o
State shall, without the Consent of Congress, . . .
engage in War, unless actually invaded, or in such imminent
Danger as will not admit of delay .” Art. I, §10,
cl. 3 (emphasis added). This limits the States’ sovereignty
(in a way not relevant here) but leaves intact their inherent power
to protect their territory.

															Notwithstanding “[t]he myth of an era of
unrestricted immigration” in the first 100 years of the Republic,
the States enacted numerous laws restricting the immigra- tion of
certain classes of aliens, including convicted criminals,
indigents, persons with contagious diseases, and (in Southern
States) freed blacks. Neuman, The Lost Century of American
Immigration (1776–1875), 93 Colum. L. Rev. 1833, 1835,
1841–1880 (1993). State laws not only pro- vided for the removal of
unwanted immigrants but also imposed penalties on unlawfully
present aliens and those who aided their immigration.[ 2 ] Id., at 1883.

															In fact, the controversy surrounding the Alien
and Sedition Acts involved a debate over whether, under the
Constitution, the States had exclusive authority to enact
such immigration laws. Criticism of the Sedition Act has become a
prominent feature of our First Amendment jurisprudence, see, e.g., New York Times Co. v. Sullivan , 376 U.S.
254 , 273–276 (1964), but one of the Alien Acts[ 3 ] also aroused controversy at the time:

															“ Be it enacted by the Senate and House
of Representatives of the United States of America in Congress
assembled , That it shall be lawful for the President of the
United States at any time during the continuance of this act, to order all such aliens as he shall judge dangerous to
the peace and safety of the United States, or shall have reasonable
grounds to suspect are concerned in any treasonable or secret
machinations against the government thereof, to depart out of the
territory of the United States . . . .” An Act
concerning Aliens, 1Stat. 570, 570–571.

															The Kentucky and Virginia Resolutions, written
in denunciation of these Acts, insisted that the power to exclude
unwanted aliens rested solely in the States. Jefferson’s Kentucky
Resolutions insisted “that alien friends are under the jurisdiction
and protection of the laws of the state wherein they are [and] that
no power over them has been delegated to the United States, nor
prohibited to the individual states, distinct from their power over
citizens.” Kentucky Resolutions of 1798, reprinted in J. Powell,
Languages of Power: A Sourcebook of Early American Constitutional
History 131 (1991). Madison’s Virginia Resolutions likewise
contended that the Alien Act purported to give the President “a
power nowhere delegated to the federal government.” Virginia
Resolutions of 1798, reprinted in Powell, supra, at 134
(emphasis omitted). Notably, moreover, the Federalist proponents of
the Act defended it primarily on the ground that “[t]he removal of
aliens is the usual preliminary of hostility” and could therefore
be justified in exercise of the Federal Government’s war powers.
Massachussets Resolutions in Reply to Virginia, reprinted in
Powell, supra, at 136.

															In Mayor of New York v. Miln , this
Court considered a New York statute that required the commander of
any ship arriving in New York from abroad to disclose “the name,
place of birth, and last legal settlement, age and occupation
. . . of all passengers . . . with the
intention of proceeding to the said city.” 11 Pet., at 130–131.
After discussing the sovereign authority to regulate the entrance
of foreigners described by De Vattel, the Court said:

															“The power . . . of New York to
pass this law having undeniably existed at the formation of the
constitution, the simply inquiry is, whether by that instrument it
was taken from the states, and granted to congress; for if it were
not, it yet remains with them.” Id., at 132.

															And the Court held that it remains. Id., at 139.

															II

															One would conclude from the foregoing that
after the adoption of the Constitution there was some doubt about
the power of the Federal Government to control immigration, but no
doubt about the power of the States to do so. Since the founding
era (though not immediately), doubt about the Federal Government’s
power has disappeared. Indeed, primary responsibility for
immigration policy has shifted from the States to the Federal
Government. Congress exercised its power “[t]o establish an uniform
Rule of Naturalization,” Art. I, §8, cl. 4, very early
on, see An Act to establish an uniform Rule of Naturalization,
1Stat. 103. But with the fleeting exception of the Alien Act,
Congress did not enact any legislation regulating immigration for the better part of a century. In 1862,
Congress passed “An Act to prohibit the ‘Coolie Trade’ by American
Citizens in American Vessels,” which prohibited “procuring [Chinese
nationals] . . . to be disposed of, or sold, or
transferred, for any term of years or for any time what- ever, as
servants or apprentices, or to be held to service or labor.”
12Stat. 340. Then, in 1875, Congress amended that act to bar
admission to Chinese, Japanese, and other Asian immigrants who had
“entered into a contract or agreement for a term of service within
the United States, for lewd and immoral purposes.” An act
supplementary to the acts in relation to immigration, ch. 141,
18Stat. 477. And in 1882, Congress enacted the first general immi-
gration statute. See An act to regulate Immigration, 22Stat. 214.
Of course, it hardly bears mention that Federal immigration law is
now extensive.

															I accept that as a valid exercise of federal
power—not because of the Naturalization Clause (it has no necessary
connection to citizenship) but because it is an inherent attribute
of sovereignty no less for the United States than for the States.
As this Court has said, it is an “ ‘accepted maxim of
international law, that every sovereign nation has the power, as
inherent in sovereignty, and essential to self-preservation, to
forbid the entrance of foreigners within its dominions.’ ” Fong Yue Ting v. United States , 149 U.S.
698 , 705 (1893) (quoting Ekiu v. United States , 142 U.S.
651 , 659 (1892)). That is why there was no need to set forth
control of immigration as one of the enumer- ated powers of
Congress, although an acknowledgment of that power (as well as of
the States’ similar power, subject to federal abridgment) was
contained in Art. I, §9, which provided that “[t]he Migration
or Importation of such Persons as any of the States now existing
shall think proper to admit, shall not be prohibited by the
Congress prior to the Year one thousand eight hundred and
eight . . . .”

															In light of the predominance of federal
immigration restrictions in modern times, it is easy to lose sight
of the States’ traditional role in regulating immigration—and to
overlook their sovereign prerogative to do so. I accept as a given
that State regulation is excluded by the Constitution when (1) it
has been prohibited by a valid federal law, or (2) it conflicts
with federal regulation—when, for example, it admits those whom
federal regulation would exclude, or excludes those whom federal
regulation would admit.

															Possibility (1) need not be considered here:
there is no federal law prohibiting the States’ sovereign power to
ex- clude (assuming federal authority to enact such a law). The
mere existence of federal action in the immigration area—and the
so-called field preemption arising from that action, upon which the
Court’s opinion so heavily relies, ante, at 9–11—cannot be
regarded as such a prohibition. We are not talking here about a
federal law prohibiting the States from regulating bubble-gum
advertising, or even the construction of nuclear plants. We are
talking about a federal law going to the core of state
sovereignty: the power to exclude. Like elimination of the States’
other inherent sovereign power, immunity from suit, elimina- tion
of the States’ sovereign power to exclude requires that “Congress
. . . unequivocally expres[s] its intent to abrogate,” Seminole Tribe of Fla. v. Florida , 517 U.S.
44 , 55 (1996) (internal quotation marks and citation omitted).
Implicit “field preemption” will not do.

															Nor can federal power over illegal immigration
be deemed exclusive because of what the Court’s opinion
solicitously calls “foreign countries[ ’] concern[s] about the
status, safety, and security of their nationals in the United
States,” ante , at 3. The Constitution gives all those on our
shores the protections of the Bill of Rights—but just as those
rights are not expanded for foreign nationals because of their
countries’ views (some countries, for example, have recently
discovered the death penalty to be barbaric), neither are the
fundamental sovereign powers of the States abridged to accommodate
foreign countries’ views. Even in its international relations, the
Federal Government must live with the inconvenient fact that it is
a Union of independent States, who have their own sovereign powers.
This is not the first time it has found that a nuisance and a
bother in the conduct of foreign policy. Four years ago, for
example, the Government importuned us to interfere with thoroughly
constitutional state judicial procedures in the criminal trial of
foreign nationals because the international community, and even an
opinion of the International Court of Justice, disapproved them.
See Medellín v. Texas , 552 U.S.
491 (2008). We rejected that request, as we should reject the
Executive’s invocation of foreign-affairs considerations here.
Though it may upset foreign powers—and even when the Federal
Government desperately wants to avoid upsetting foreign powers—the
States have the right to protect their borders against foreign
nationals, just as they have the right to execute foreign nationals
for murder.

															What this case comes down to, then, is whether
the Arizona law conflicts with federal immigration law—whether it
excludes those whom federal law would admit, or admits those whom
federal law would exclude. It does not purport to do so. It applies
only to aliens who neither possess a privilege to be present under
federal law nor have been removed pursuant to the Federal
Government’s inherent authority. I proceed to consider the
challenged provisions in detail.

															§2(B)

															“For any lawful stop, detention or arrest
made by a law enforcement official . . . in the
enforcement of any other law or ordinance of a county, city or town
or this state where reasonable suspicion exists that the person is
an alien and is unlawfully present in the United States, a
reasonable attempt shall be made, when practicable, to determine
the immigration status of the person, except if the determination
may hinder or obstruct an investigation. Any person who is arrested
shall have the person’s immigration status determined before the
person is released. . . .” S. B. 1070, §2(B), as
amended , Ariz. Rev. Stat. Ann. §11–1051(B) (West 2012).

															The Government has conceded that “even before
Section 2 was enacted, state and local officers had state-law
authority to inquire of DHS [the Department of Homeland Security]
about a suspect’s unlawful status and other- wise cooperate with
federal immigration officers.” Brief for United States 47 (citing
App. 62, 82); see also Brief for United States 48–49. That
concession, in my view, ob- viates the need for further inquiry.
The Government’s conflict-pre-emption claim calls on us “to
determine whether, under the circumstances of this particular
case , [the State’s] law stands as an obstacle to the
accomplishment and execution of the full purposes and objectives of
Congress.” Hines v. Davidowitz , 312 U.S.
52 , 67 (1941) (emphasis added). It is impossible to make such a
finding without a factual record concerning the manner in which
Arizona is implementing these provisions—something the Government’s
pre-enforcement challenge has pretermitted. “The fact that [a law]
might operate unconstitutionally under some conceivable set of
circumstances is insuf- ficient to render it wholly invalid, since
we have not recognized an ‘overbreadth’ doctrine outside the
limited context of the First Amendment.” United States v. Sal- erno , 481 U.S.
739 , 745 (1987). And on its face, §2(B) merely tells state
officials that they are authorized to do something that they were,
by the Government’s con- cession, already authorized to do.

															The Court therefore properly rejects the
Government’s challenge, recognizing that, “[a]t this stage, without
the benefit of a definitive interpretation from the state courts,
it would be inappropriate to assume §2B will be construed in a way
that creates a conflict with federal law.” Ante, at 23.
Before reaching that conclusion, however, the Court goes to great
length to assuage fears that “state officers will be required to
delay the release of some detainees for no reason other than to
verify their immigration status.” Ante, at 22. Of course,
any investigatory detention, including one under §2(B), may become
an “unreasonable . . . seizur[e],” U. S. Const.,
Amdt. IV, if it lasts too long. See Illinois v. Caballes , 543 U.S.
405 , 407 (2005). But that has nothing to do with this case, in
which the Government claims that §2(B) is pre-empted by federal
immigration law, not that anyone’s Fourth Amendment rights have
been violated. And I know of no reason why a protracted detention
that does not violate the Fourth Amendment would contradict or
conflict with any federal immigration law.

															§6

															“A peace officer, without a warrant, may
arrest a person if the officer has probable cause to believe
. . . [t]he person to be arrested has committed any
public offense that makes the person removable from the United
States.” S. B. 1070, §6(A)(5), Ariz. Rev. Stat. Ann.
§13–3883(A)(5) (West Supp. 2011).

															This provision of S. B. 1070 expands the
statutory list of offenses for which an Arizona police officer may
make an arrest without a warrant. See §13–3883. If an officer has
probable cause to believe that an individual is “removable” by
reason of a public offense, then a warrant is not required to make
an arrest. The Government’s primary contention is that §6 is
pre-empted by federal immigration law because it allows state
officials to make arrests “without regard to federal priorities.”
Brief for United States 53. The Court’s opinion focuses on limits
that Congress has placed on federal officials’ authority to
arrest remov- able aliens and the possibility that state officials
will make arrests “to achieve [Arizona’s] own immigration policy”
and “without any input from the Federal Government.” Ante, at 17.

															Of course on this pre-enforcement record there
is no reason to assume that Arizona officials will ignore federal
immigration policy (unless it be the questionable policy of not
wanting to identify illegal aliens who have committed offenses that
make them removable). As Arizona points out, federal law expressly
provides that state officers may “cooperate with the Attorney
General in the identification, apprehension, detention, or removal
of aliens not lawfully present in the United States,” 8
U. S. C. §1357(g)(10)(B); and “cooperation” requires
neither identical efforts nor prior federal approval. It is
consistent with the Arizona statute, and with the “cooperat[ive]”
system that Congress has created, for state officials to arrest a
removable alien, contact federal immigration authorities, and
follow their lead on what to do next. And it is an assault on logic
to say that identifying a removable alien and holding him for
federal determination of whether he should be removed “violates the
principle that the removal process is entrusted to the discretion
of the Federal Government,” ante, at 18. The State’s
detention does not represent commencement of the removal process
unless the Federal Government makes it so.

															But that is not the most important point. The
most important point is that, as we have discussed, Arizona is entitled to have “its own immigration policy”—including a
more rigorous enforcement policy—so long as that does not conflict
with federal law. The Court says, as though the point is utterly
dispositive, that “it is not a crime for a removable alien to
remain present in the United States,” ante, at 15. It is not
a federal crime, to be sure. But there is no reason Arizona cannot
make it a state crime for a removable alien (or any illegal alien,
for that matter) to remain present in Arizona.

															The Court quotes 8 U. S. C. §1226(a),
which provides that, “[o]n a warrant issued by the Attorney
General, an alien may be arrested and detained pending a decision
on whether the alien is to be removed from the United States.”
Section 1357(a)(2) also provides that a federal immigration
official “shall have power without warrant . . . to
arrest any alien in the United States, if he has reason to believe
that the alien so arrested is in the United States in violation of
any [federal immigration] law or regulation and is likely to escape
before a warrant can be obtained for his arrest.” But statutory
limitations upon the actions of federal officers in enforcing the
United States’ power to protect its borders do not on their face
apply to the actions of state officers in enforcing the State’s
power to protect its borders. There is no more reason to read these
provisions as implying that state officials are subject to similar
limitations than there is to read them as implying that only
federal officials may arrest removable aliens. And in any event neither implication would constitute the sort of clear
elimination of the States’ sovereign power that our cases
demand.

															The Court raises concerns about “unnecessary
harassment of some aliens . . . whom federal officials
determine should not be removed.” Ante, at 17. But we have
no license to assume, without any support in the record, that
Arizona officials would use their arrest authority under §6 to
harass anyone. And it makes no difference that federal officials
might “determine [that some unlawfully present aliens] should not
be removed,” ibid. They may well determine not to remove
from the United States aliens who have no right to be here; but
unless and until these aliens have been given the right to remain,
Arizona is entitled to arrest them and at least bring them
to federal officials’ attention, which is all that §6 necessarily
entails. (In my view, the State can go further than this, and
punish them for their unlawful entry and presence in Arizona.)

															The Government complains that state officials
might not heed “federal priorities.” Indeed they might not,
particularly if those priorities include willful blindness or
delib- erate inattention to the presence of removable aliens in
Arizona. The State’s whole complaint—the reason this law was passed
and this case has arisen—is that the citizens of Arizona believe
federal priorities are too lax. The State has the sovereign power
to protect its borders more rigorously if it wishes, absent any
valid federal prohibition. The Executive’s policy choice of lax
federal enforcement does not constitute such a prohibition.

															§3

															“In addition to any violation of federal
law, a person is guilty of willful failure to complete or carry an
alien registration document if the person is in violation of 8
[U. S. C.] §1304(e) or §1306(a).” S. B. 1070, §3(A),
as amended, Ariz. Rev. Stat. Ann. §13–1509(A).

															It is beyond question that a State may make
violation of federal law a violation of state law as well. We have
held that to be so even when the interest protected is a
distinctively federal interest, such as protection of the dignity
of the national flag, see Halter v. Nebraska , 205 U.S.
34 (1907), or protection of the Federal Government’s ability to
recruit soldiers, Gilbert v. Minnesota , 254 U.S.
325 (1920). “[T]he State is not inhibited from making the
national purposes its own purposes to the extent of exerting its
police power to prevent its own citizens from obstructing the
accomplishment of such purposes.” Id., at 331 (internal
quotation marks omitted). Much more is that so when, as here, the
State is protecting its own interest, the integrity of its
borders. And we have said that explicitly with regard to illegal
immigration: “Despite the exclusive federal control of this
Nation’s borders, we cannot conclude that the States are without
any power to deter the influx of persons entering the United States
against federal law, and whose numbers might have a discernible
impact on traditional state concerns.” Plyler v. Doe , 457 U.S.
202 , 228, n. 23 (1982).

															The Court’s opinion relies upon Hines v. Davidowitz , supra. Ante , at 9–10. But that case did
not, as the Court believes, establish a “field preemption” that
implicitly eliminates the States’ sovereign power to exclude those
whom federal law excludes. It held that the States are not
permitted to establish “additional or auxiliary” registration
requirements for aliens. 312 U. S., at 66–67. But §3 does not
establish additional or auxiliary registration requirements. It
merely makes a violation of state law the very same failure
to register and failure to carry evidence of registration that are
violations of federal law. Hines does not prevent the State
from relying on the federal registration system as “an available
aid in the enforcement of a number of statutes of the state
applicable to aliens whose constitutional validity has not been
questioned.” Id., at 75–76 (Stone, J., dissenting). One such
statute is Arizona’s law forbidding illegal aliens to collect
unemployment benefits, Ariz. Rev. Stat. Ann. §23–781(B) (West
2012). To enforce that and other laws that validly turn on alien
status, Arizona has, in Justice Stone’s words, an interest in
knowing “the number and whereabouts of aliens within the state” and
in having “a means of their identification,” 312 U. S., at 75.
And it can punish the aliens’ failure to comply with the provisions
of federal law that make that knowledge and identification
possible.

															In some areas of uniquely federal
concern— e.g., fraud in a federal administrative process
( Buckman Co. v. Plaintiffs’ Legal Comm. , 531 U.S.
341 (2001)) or perjury in violation of a federally required
oath ( In re Loney , 134 U.S.
372 (1890))—this Court has held that a State has no legitimate
interest in enforcing a federal scheme. But the federal alien
registration system is certainly not of uniquely federal interest.
States, private entities, and individuals rely on the federal
registration system (including the E-Verify program) on a regular
basis. Arizona’s legitimate in- terest in protecting (among other
things) its unemployment-benefits system is an entirely adequate
basis for making the violation of federal registration and carry
requirements a violation of state law as well.

															The Court points out, however, ante, at
11, that in some respects the state law exceeds the punishments
prescribed by federal law: It rules out probation and pardon, which
are available under federal law. The answer is that it makes no
difference. Illegal immigrants who violate §3 violate Arizona law. It is one thing to say that the Supremacy
Clause prevents Arizona law from excluding those whom federal law
admits. It is quite something else to say that a violation of
Arizona law cannot be punished more severely than a violation of
federal law. Especially where (as here) the State is defending its
own sovereign interests, there is no precedent for such a
limitation. The sale of illegal drugs, for example, ordinarily
violates state law as well as federal law, and no one thinks that
the state penalties cannot exceed the federal. As I have discussed,
moreover, “field preemption” cannot establish a prohibition of
additional state penalties in the area of immigration.

															Finally, the Government also suggests that §3
poses an obstacle to the administration of federal immigration law,
see Brief for United States 31–33, but “there is no conflict in
terms, and no possibility of such conflict, [if] the state statute
makes federal law its own,” California v. Zook , 336 U.S.
725 , 735 (1949).

															It holds no fear for me, as it does for the
Court, that “[w]ere §3 to come into force, the State would have the
power to bring criminal charges against individuals for violating a
federal law even in circumstances where fed- eral officials in
charge of the comprehensive scheme determine that prosecution would
frustrate federal policies.” Ante, at 11. That seems to me
entirely appropriate when the State uses the federal law (as it
must) as the criterion for the exercise of its own power ,
and the implementation of its own policies of excluding
those who do not belong there. What I do fear—and what Arizona and
the States that support it fear—is that “federal policies” of
nonenforcement will leave the States helpless before those evil
effects of illegal immigration that the Court’s opinion dutifully
recites in its prologue ( ante, at 6) but leaves unremedied
in its disposition.

															§5(C)

															“It is unlawful for a person who is
unlawfully present in the United States and who is an unauthorized
alien to knowingly apply for work, solicit work in a public place
or perform work as an employee or independent contractor in this
state.” S. B. 1070, §5(C), as amended, Ariz. Rev. Stat. Ann.
§13–2928(C).

															Here, the Court rightly starts with De
Canas v. Bica , 424 U.S.
351 (1976), which involved a California law providing that
“ ‘[n]o employer shall knowingly employ an alien who is not
entitled to lawful residence in the United States if such
employment would have an adverse effect on lawful resident
workers.’ ” Id. , at 352 (quoting California Labor Code
Ann. §2805(a)). This Court concluded that the California law was
not pre-empted, as Congress had neither occupied the field of
“regulation of employment of illegal aliens” nor expressed “the
clear and manifest purpose” of displacing such state regulation. Id., at 356–357 (internal quotation marks omitted). Thus, at
the time De Canas was decided, §5(C) would have been
indubitably lawful.

															The only relevant change is that Congress has
since enacted its own restrictions on employers who hire illegal
aliens, 8 U. S. C. §1324a, in legislation that also
includes some civil (but no criminal) penalties on illegal aliens
who accept unlawful employment. The Court concludes from this
(reasonably enough) “that Congress made a deliberate choice not to
impose criminal penalties on aliens who seek, or engage in,
unauthorized employment,” ante , at 13. But that is not the
same as a deliberate choice to prohibit the States from imposing
criminal penalties. Congress’s intent with regard to exclusion of
state law need not be guessed at, but is found in the law’s express
pre-emption provision, which excludes “any State or local law
impos- ing civil or criminal sanctions (other than through
licensing and similar laws) upon those who employ , or
recruit or refer for a fee for employment, unauthorized
aliens,” §1324a(h)(2) (emphasis added). Common sense, reflected in
the canon expressio unius est exclusio alterius , suggests
that the specification of pre-emption for laws punishing “those who
employ” implies the lack of pre-emption for other laws, including
laws punishing “those who seek or accept employment.”

															The Court has no credible response to this. It
quotes our jurisprudence to the effect that an “express pre-emption
provisio[n] does not bar the ordinary working of conflict
pre-emption principles.” Ante, at 14 (quoting Geier v. American Honda Motor Co. , 529 U.S.
861 , 869 (2000) (internal quotation marks omitted)). True
enough— conflict preemption principles. It then goes on say
that since “Congress decided it would be inappropriate to impose
criminal penalties on aliens who seek or engage in unauthorized
employment,” “[i]t follows that a state law to the contrary is an
obstacle to the regulatory system Congress chose.” Ante, at
15. For “ ‘[w]here a comprehensive federal scheme
intentionally leaves a portion of the regulated field without
controls, then the pre-emptive inference can be
drawn.’ ” Ibid. (quoting Puerto Rico Dept. of
Consumer Affairs v. ISLA Petroleum Corp. , 485 U.S.
495 , 503 (1988)). All that is a classic description not of conflict pre-emption but of field pre-emption, which
(concededly) does not occur beyond the terms of an express
pre-emption provision.

															The Court concludes that §5(C) “would interfere
with the careful balance struck by Congress,” ante, at 15,
(another field pre-emption notion, by the way) but that is easy to
say and impossible to demonstrate. The Court relies primarily on
the fact that “[p]roposals to make unauthorized work a criminal
offense were debated and discussed during the long process of
drafting [the Immigration Reform and Control Act of 1986 (IRCA)],”
“[b]ut Congress rejected them.” Ante, at 14. There is no
more reason to believe that this rejection was expressive of a
desire that there be no sanctions on employees, than expressive of
a desire that such sanctions be left to the States. To tell the
truth, it was most likely expressive of what inaction ordinarily
expresses: nothing at all. It is a “naïve assumption that the
failure of a bill to make it out of committee, or to be adopted
when reported to the floor, is the same as a congressional
rejection of what the bill contained.” Crosby v. National
Foreign Trade Council , 530 U.S.
363 , 389 (2000) (Scalia, J., concurring in judgment) (internal
quotation marks and alterations omitted).

															*  *  *

															The brief for the Government in this case
asserted that “the Executive Branch’s ability to exercise
discretion and set priorities is particularly important because of
the need to allocate scarce enforcement resources wisely.” Brief
for United States 21. Of course there is no reason why the Federal
Executive’s need to allocate its scarce enforcement
resources should disable Arizona from devoting its resources
to illegal immigration in Arizona that in its view the Federal
Executive has given short shrift. Despite Congress’s prescription
that “the immigration laws of the United States should be enforced
vigorously and uniformly,” IRCA §115, 100Stat. 3384, Arizona
asserts without contradiction and with supporting citations:

															“[I]n the last decade federal enforcement
efforts have focused primarily on areas in California and Texas,
leaving Arizona’s border to suffer from comparative neglect. The
result has been the funneling of an increasing tide of illegal
border crossings into Arizona. Indeed, over the past decade, over a
third of the Nation’s illegal border crossings occurred in
Arizona.” Brief for Petitioners 2–3 (footnote omitted).

															Must Arizona’s ability to protect its borders
yield to the reality that Congress has provided inadequate funding
for federal enforcement—or, even worse, to the Executive’s unwise
targeting of that funding?

															But leave that aside. It has become clear that
federal enforcement priorities—in the sense of priorities based on
the need to allocate “scarce enforcement resources”—is not the
problem here. After this case was argued and while it was under
consideration, the Secretary of Homeland Security announced a
program exempting from immi- gration enforcement some 1.4 million
illegal immigrants under the age of 30.[ 4 ] If an individual unlawfully present in the United
States

															“•came to the United States under the age of
sixteen;

															“•has continuously resided in the United
States for at least five years . . . ,

															“•is currently in school, has graduated from
high school, has obtained a general education development
certificate, or is an honorably discharged veteran
. . . ,

															“•has not been convicted of a [serious crime];
and

															“•is not above the age of thirty,”[ 5 ]

															then U. S. immigration officials have been
directed to “defe[r] action” against such individual “for a period
of two years, subject to renewal.”[ 6 ] The husbanding of scarce enforcement resources can
hardly be the justification for this, since the considerable
administrative cost of conducting as many as 1.4 million background
checks, and ruling on the biennial requests for dispensation that
the nonenforcement program envisions, will necessarily be deducted from immigration enforcement. The President said at
a news conference that the new program is “the right thing to do”
in light of Congress’s failure to pass the Administration’s
proposed revision of the Immigration Act.[ 7 ] Perhaps it is, though Arizona may not think so. But
to say, as the Court does, that Arizona contradicts federal
law by enforcing applications of the Immigration Act that the
President declines to enforce boggles the mind.

															The Court opinion’s looming specter of
inutterable horror—“[i]f §3 of the Arizona statute were valid,
every State could give itself independent authority to prosecute
fed- eral registration violations,” ante, at 10—seems to me
not so horrible and even less looming. But there has come to pass,
and is with us today, the specter that Arizona and the States that
support it predicted: A Federal Government that does not want to
enforce the immigration laws as written, and leaves the States’
borders unprotected against immigrants whom those laws would
exclude. So the issue is a stark one. Are the sovereign States at
the mercy of the Federal Executive’s refusal to enforce the
Nation’s immigration laws?

															A good way of answering that question is to ask:
Would the States conceivably have entered into the Union if the
Constitution itself contained the Court’s holding? Today’s judgment
surely fails that test. At the Constitutional Convention of 1787,
the delegates contended with “the jealousy of the states with
regard to their sovereignty.” 1 Records of the Federal Convention
19 (M. Farrand ed. 1911) (statement of Edmund Randolph). Through
ratification of the fundamental charter that the Convention
produced, the States ceded much of their sovereignty to the Federal
Government. But much of it remained jealously guarded—as reflected
in the innumerable proposals that never left Independence Hall.
Now, imagine a provision—perhaps inserted right after Art. I,
§8, cl. 4, the Naturalization Clause—which included among the
enumerated powers of Congress “To establish Limitations upon
Immigration that will be exclusive and that will be enforced only
to the extent the President deems appropriate.” The delegates to
the Grand Convention would have rushed to the exits.

															As is often the case, discussion of the dry
legalities that are the proper object of our attention suppresses
the very human realities that gave rise to the suit. Arizona bears
the brunt of the country’s illegal immigration problem. Its
citizens feel themselves under siege by large numbers of illegal
immigrants who invade their property, strain their social services,
and even place their lives in jeopardy. Federal officials have been
unable to remedy the problem, and indeed have recently shown that
they are unwilling to do so. Thousands of Arizona’s estimated
400,000 illegal immigrants—including not just children but men and
women under 30—are now assured immunity from enforcement, and will
be able to compete openly with Ari- zona citizens for
employment.

															Arizona has moved to protect its sovereignty—not
in contradiction of federal law, but in complete compliance with
it. The laws under challenge here do not extend or revise federal
immigration restrictions, but merely enforce those restrictions
more effectively. If securing its territory in this fashion is not
within the power of Arizona, we should cease referring to it as a
sovereign State. I dissent. Notes 1 Many of the 17th-, 18th-,
and 19th-century commentators maintained that states should exclude
foreigners only for good reason. Pufendorf, for example, maintained
that states are generally expected to grant “permanent settlement
to strangers who have been driven from their former home,” though
acknowledging that, when faced with the prospect of mass
immigration, “every state may decide after its own custom what
privilege should be granted in such a situation.” 2 Of the Law of
Nature and Nations, bk. III, ch. III, §10, p. 366 (C. Oldfather
& W. Oldfather eds. 1934). See generally Cleveland, Powers
Inherent in Sovereignty: Indians, Aliens, Territories, and the
Nineteenth Century Origins of Plenary Power over Foreign Affairs,
81 Tex. L. Rev. 1, 83–87 (2002). But the authority to exclude
was universally accepted as inherent in sovereignty, whatever
prudential limitations there might be on its exercise. 2 E.g., Va. Code
Tit. 54, ch. 198, §39 (1849) (“If a master of a vessel or other
person, knowingly, import or bring into this state, from any place
out of the United States , any person convicted of crime
. . . he shall be confined in jail for three months, and
be fined one hundred dollars”). 3 There were two Alien
Acts, one of which dealt only with enemyaliens. An Act respecting
Alien Enemies, 1Stat. 577. 4 Preston & Cushman,
Obama to Permit Young Migrants to Remain in U. S., N. Y.
Times, June 16, 2012, p. A1. 5 Memorandum from Janet
Napolitano, Secretary of Homeland Security, to David V. Aguilar,
Acting Commissioner, U. S. Customs and Border Protection;
Alejandro Mayorkas, Director, U. S. Citizenshipand Immigration
Services; and John Morton, Director, U. S. Immigra-tion and
Customs Enforcement, p. 1 (June 15, 2012), online at
http://www.dhs.gov (all Internet materials as visited June 22,
2012, and available in Clerk of Court’s case file). 6 Id., at
2. 7 Remarks by the President
on Immigration (June 15, 2012), online at
http://www.whitehouse.gov. SUPREME COURT OF THE UNITED STATES

															_________________

															No. 11–182

															_________________

															ARIZONA, et al., PETITIONERS v. UNITED STATES

															on writ of certiorari to the united states
court of appeals for the ninth circuit

															[June 25, 2012]

															Justice Thomas, concurring in part and
dissenting in part.

															I agree with Justice Scalia that federal
immigration law does not pre-empt any of the challenged provisions
of S. B. 1070. I reach that conclusion, however, for the
simple reason that there is no conflict between the “ordinary
meanin[g]” of the relevant federal laws and that of the four
provisions of Arizona law at issue here. Wyeth v. Levine , 555 U.S.
555 , 588 (2009) (Thomas, J., concurring in judgment)
(“Pre-emption analysis should not be a freewheeling judicial
inquiry into whether a state statute is in tension with federal
objectives, but an inquiry into whether the ordinary meanings of
state and federal law conflict” (brackets; internal quotation marks
omitted)).

															Section 2(B) of S. B. 1070 provides that,
when Arizona law enforcement officers reasonably suspect that a
person they have lawfully stopped, detained, or arrested is
unlawfully present, “a reasonable attempt shall be made, when
practicable, to determine the immigration status of the person”
pursuant to the verification procedure established by Congress in 8
U. S. C. §1373(c). Ariz. Rev. Stat. Ann. §11–1051(B)
(West 2012). Nothing in the text of that or any other federal
statute prohibits Arizona from directing its officers to make
immigration-related inquiries in these situations. To the contrary,
federal law expressly states that “no State or local government
entity may be prohib- ited, or in any way restricted, from sending
to or receiving from” federal officials “information regarding the
immigration status” of an alien. 8 U. S. C. §1644. And,
federal law imposes an affirmative obligation on federal officials
to respond to a State’s immigration-related inquiries.
§1373(c).

															Section 6 of S. B. 1070 authorizes Arizona
law enforcement officers to make warrantless arrests when there is
probable cause to believe that an arrestee has committed a public
offense that renders him removable under federal immigration law.
States, as sovereigns, have inherent authority to conduct arrests
for violations of federal law, unless and until Congress removes
that authority. See United States v. Di Re , 332 U.S.
581 , 589 (1948) (holding that state law determines the validity
of a warrantless arrest for a violation of federal law “in the
absence of an applicable federal statute”). Here, no federal
statute purports to withdraw that authority. As Justice Scalia
notes, ante, at 12 (opinion concurring in part and
dissenting in part), federal law does limit the authority of federal officials to arrest removable aliens, but those
statutes do not apply to state officers. And, federal law
expressly recognizes that state officers may “cooperate with the
Attorney General” in the “apprehension” and “detention” of “aliens
not lawfully present in the United States.” §1357(g)(10)(B).
Nothing in that statute indicates that such cooperation requires a
prior “request, approval, or other instruction from the Federal
Government.” Ante, at 18 (majority opinion).

															Section 3 of S. B. 1070 makes it a crime
under Arizona law for an unlawfully present alien to willfully fail
to complete or carry an alien registration document in violation of
8 U. S. C. §1304(e) and §1306(a). Section 3 simply
incorporates federal registration standards. Unlike the Court, I
would not hold that Congress pre-empted the field of enforcing
those standards. “[O]ur recent cases have frequently rejected field
pre-emption in the absence of statutory language expressly
requiring it.” Camps Newfound/Owatonna, Inc. v. Town of
Harrison , 520 U.S.
564 , 617 (1997) (Thomas, J., dissenting); see, e.g., New York State Dept. of Social Servs. v. Dublino , 413 U.S.
405 , 415 (1973). Here, nothing in the text of the relevant
federal statutes indicates that Congress intended enforcement of
its registration requirements to be exclusively the province of the
Federal Government. That Congress created a “full set of standards
governing alien registration,” ante, at 10 (majority
opinion), merely indicates that it intended the scheme to be
capable of working on its own, not that it wanted to preclude the
States from enforcing the federal standards. Hines v. Davidowitz , 312 U.S.
52 (1941), is not to the contrary. As Justice Scalia explains, ante, at 14, Hines at most holds that federal law
pre-empts the States from creating additional registration
requirements. But here, Arizona is merely seeking to enforce the
very registration requirements that Congress created.

															Section 5(C) of S. B. 1070 prohibits
unlawfully present aliens from knowingly applying for, soliciting,
or performing work in Arizona. Section 5(C) operates only on
individuals whom Congress has already declared ineligible to work
in the United States. Nothing in the text of the federal
immigration laws prohibits States from imposing their own criminal
penalties on such individuals. Fed- eral law expressly pre-empts
States from “imposing civil or criminal sanctions (other than
through licensing and similar laws) upon those who employ ,
or recruit or refer for a fee for employment, unauthorized aliens.”
8 U. S. C. §1324a(h)(2) (emphasis added). But it leaves
States free to impose criminal sanctions on the employees
themselves.

															Despite the lack of any conflict between the
ordinary meaning of the Arizona law and that of the federal laws at
issue here, the Court holds that various provisions of the Arizona
law are pre-empted because they “stan[d] as an obstacle to the
accomplishment and execution of the full purposes and objectives of
Congress.” Hines , supra , at 67. I have explained that
the “purposes and objectives” theory of implied pre-emption is
inconsistent with the Constitution because it invites courts to
engage in freewheeling speculation about congressional purpose that
roams well beyond statutory text. See Wyeth , 555 U. S.,
at 604 (opinion concurring in judgment); see also Williamson v. Mazda Motor of America, Inc. , 562 U. S. ___, ___–___
(2011) (opinion concurring in judgment) (slip op., at 2–3); Haywood v. Drown , 556 U.S.
729 , 767 (2009) (dissenting opinion). Under the Supremacy
Clause, pre-emptive effect is to be given to congressionally
enacted laws, not to judicially divined legislative purposes. See Wyeth , supra , at 604 (Thomas, J., concurring in
judgment). Thus, even assuming the existence of some tension
between Arizona’s law and the supposed “purposes and objectives” of
Congress, I would not hold that any of the provisions of the
Arizona law at issue here are pre-empted on that basis. SUPREME COURT OF THE UNITED STATES

															_________________

															No. 11–182

															_________________

															ARIZONA, et al., PETITIONERS v. UNITED STATES

															on writ of certiorari to the united states
court of appeals for the ninth circuit

															[June 25, 2012]

															Justice Alito, concurring in part and
dissenting in part.

															This case concerns four provisions of Arizona’s
Support Our Law Enforcement and Safe Neighborhoods Act, S. B. 1070.
Section 2(B) requires Arizona law enforcement officers to make a
“reasonable attempt,” “when practicable,” to ascertain the
immigration status of any person whom an officer lawfully stops,
detains, or arrests “where reasonable suspicion exists that the
person is an alien and is unlawfully present in the United States.”
Ariz. Rev. Stat. Ann. §11–1051(B) (West 2012). Section 3 provides
that an alien who willfully fails “to complete or carry an alien
registration document” in violation of 8 U. S. C.
§1304(e) or §1306(a) is guilty of a misdemeanor. Ariz. Rev. Stat.
Ann. §13–1509(A) (West Supp. 2011). Section 5(C) makes it a
misdemeanor for an unauthorized alien who is unlawfully present in
the United States “to knowingly apply for work, solicit work in a
public place or perform work as an employee or independent
contractor.” Ariz. Rev. Stat. Ann. §13–2928(C). And §6 authorizes
Arizona law enforcement officers to arrest without a warrant any
person whom the officer has probable cause to believe “has
committed any public offense that makes the person removable from
the United States.” Ariz. Rev. Stat. Ann. §13–3883(A)(5).

															I agree with the Court that §2(B) is not
pre-empted. That provision does not authorize or require Arizona
law enforcement officers to do anything they are not already
allowed to do under existing federal law. The United States’
argument that §2(B) is pre-empted, not by any federal statute or
regulation, but simply by the Executive’s current enforcement
policy is an astounding assertion of federal executive power that
the Court rightly rejects.

															I also agree with the Court that §3 is
pre-empted by virtue of our decision in Hines v. Davidowitz , 312 U.S.
52 (1941). Our conclusion in that case that Congress had
enacted an “all-embracing system” of alien registration and that
States cannot “enforce additional or auxiliary regulations,” id., at 66–67, 74, forecloses Arizona’s attempt here to
impose additional, state-law penalties for violations of the
federal registration scheme.

															While I agree with the Court on §2(B) and §3, I
part ways on §5(C) and §6. The Court’s holding on §5(C) is
inconsistent with De Canas v. Bica , 424 U.S.
351 (1976), which held that employment regulation, even of
aliens unlawfully present in the country, is an area of traditional
state concern. Because state police powers are implicated here, our
precedents require us to presume that federal law does not displace
state law unless Congress’ intent to do so is clear and manifest. I
do not believe Congress has spoken with the requisite clarity to
justify invalidation of §5(C). Nor do I believe that §6 is invalid.
Like §2(B), §6 adds virtually nothing to the authority that Arizona
law enforcement officers already exercise. And whatever little
authority they have gained is consistent with federal law. Section 2(B) A

															Although §2(B) of the Arizona law has
occasioned much controversy, it adds nothing to the authority that
Arizona law enforcement officers, like officers in all other
States, already possess under federal law. For that reason, I agree
with the Court that §2(B) is not pre-empted.

															Section 2(B) quite clearly does not expand the
authority of Arizona officers to make stops or arrests. It is
triggered only when a “lawful stop, detention or arrest [is] made .
. . in the enforcement of any other [state or local] law or
ordinance .” Ariz. Rev. Stat. Ann. §11–1051(B) (emphasis added).
Section 2(B) thus comes into play only when an officer has
reasonable suspicion or probable cause to believe that a person has
committed a nonimmigration offense. Arizona officers plainly
possessed this authority before §2(B) took effect.

															Section 2(B) also does not expand the authority
of Arizona officers to inquire about the immigration status of
persons who are lawfully detained. When a person is stopped or
arrested and “reasonable suspicion exists that the person is an
alien and is unlawfully present in the United States,” §2(B)
instructs Arizona officers to make a “reasonable attempt,” “when
practicable,” to ascertain that person’s immigration status. Ariz.
Rev. Stat. Ann. §11–1051(B). Even before the Arizona Legislature
enacted §2(B), federal law permitted state and local officers to
make such inquiries. In 8 U. S. C. §1357(g)(10)(A),
Congress has made clear that state and local governments need not
enter into formal agreements with the Federal Government in order
“to communicate with the [Federal Government] regarding the
immigration status of any individual.” In addition, Congress has
mandated that neither the Federal Government nor any state or local
government may “prohibit, or in any way restrict, any government
entity or official from sending to, or receiving from, [the Federal
Government] information regarding the citizenship or immigration
status, lawful or unlawful, of any individual.” §1373(a); see also
§1644 (providing that “no State or local government entity may be
prohibited, or in any way restricted, from sending to or receiving
from [the Federal Government] information regarding the immigration
status, lawful or unlawful, of an alien in the United States”). And
while these provisions preserve the authority of state and local
officers to seek immigration-status information from the Federal
Government, another federal statute, §1373(c), requires that the
Federal Government respond to any such inquiries “by providing the
requested verification or status information.” It comes as no
surprise, therefore, that many States and localities permit their
law enforcement officers to make the kinds of inquiries that §2(B)
prescribes. See App. 294–298 (reporting that officers in 59
surveyed state and local jurisdictions “generally” ask arrestees
about their immigration status while 34 do not and that officers in
78 jurisdictions “generally” inform Immigration and Customs
Enforcement (ICE) when they believe an arrestee to be an
undocumented alien while only 17 do not). Congress has invited
state and local governments to make immigration-related inquiries
and has even obligated the Federal Government to respond. Through
§2(B), Arizona has taken Congress up on that invitation.

															The United States does not deny that officers
may, at their own discretion , inquire about the immigration
status of persons whom they lawfully detain. Instead, the United
States argues that §2(B) is pre-empted because it impedes
federal-state cooperation by mandating that officers verify
the immigration status of every detained person if there is reason
to believe that the person is unlawfully present in the country.
The United States claims that §2(B)’s mandate runs contrary to
federal law in that it “precludes officers from taking [the Federal
Government’s] priorities and discretion into account.” Brief for
United States 50. “[B]y interposing a mandatory state law between
state and local officers and their federal counterparts,” writes
the United States, §2(B) “stands as an obstacle to the ac-
complishment of the federal requirement of cooperation and the full
effectuation of the enforcement judgment and discretion Congress
has vested in the Executive Branch.” Ibid. (internal
quotation marks and citation omitted).

															The underlying premise of the United States’
argument seems to be that state and local officers, when left to
their own devices, generally take federal enforcement priorities
into account. But there is no reason to think that this premise is
true. And even if it were, it would not follow that §2(B)’s blanket
mandate is at odds with federal law. Nothing in the relevant
federal statutes requires state and local officers to
consider the Federal Government’s priorities before requesting
verification of a person’s immigration status. Neither 8 U. S.
C. §1357(g)(10) nor §1373(a) conditions the right of state and
local officers to communicate with the Federal Government on their
first taking account of its priorities. Nor does §1373(c) condition
the Federal Government’s obligation to answer requests for in-
formation on the sensitivity of state and local officers to its
enforcement discretion. In fact, §1373(c) dictates that the Federal
Government “shall respond” to any inquiry seeking verification of
immigration status, and that command applies whether or not the
requesting officer has bothered to consider federal priorities.
Because no federal statute requires such consideration, §2(B) does
not conflict with federal law.

															In any event, it is hard to see how state and
local offi- cers could proceed in conformity with the Federal
Government’s enforcement priorities without making an inquiry into
a suspected alien’s immigration status. For example, one of the
Federal Government’s highest priorities is the apprehension and
removal of aliens who have failed to comply with a final order of
removal. See App. 108. How can an officer identify those persons
without first in- quiring about their status? At bottom, the
discretion that ultimately matters is not whether to verify a
person’s immigration status but whether to act once the person’s
status is known. For that reason, §2(B)’s verification requirement
is not contrary to federal law because the Federal Government
retains the discretion that matters most––that is, the discretion
to enforce the law in par- ticular cases. If an Arizona officer
contacts the Federal Government to verify a person’s immigration
status and federal records reveal that the person is in the coun-
try unlawfully, the Federal Government decides, presumably based on
its enforcement priorities, whether to have the person released or
transferred to federal custody. Enforcement discretion thus lies
with the Federal Government, not with Arizona. Nothing in §2(B)
suggests otherwise.

															The United States’ attack on §2(B) is quite
remarkable. The United States suggests that a state law may be
pre-empted, not because it conflicts with a federal statute or
regulation, but because it is inconsistent with a federal agency’s
current enforcement priorities. Those priorities, however, are not
law. They are nothing more than agency policy. I am aware of no
decision of this Court recognizing that mere policy can have
pre-emptive force. Cf. Barclays Bank PLC v. Franchise Tax
Bd. of Cal. , 512 U.S.
298 , 330 (1994) (holding that “Executive Branch communications
that express federal policy but lack the force of law cannot render
unconstitutional” an “otherwise valid, congressionally condoned”
state law). If §2(B) were pre-empted at the present time because it
is out of sync with the Federal Government’s current priorities,
would it be unpre-empted at some time in the future if the agency’s
priorities changed?

															Like most law enforcement agencies, ICE does not
set out inflexible rules for its officers to follow. To the con-
trary, it provides a list of factors to guide its officers’
enforcement discretion on a case-by-case basis. See Memorandum from
John Morton, Director, ICE, to All Field Office Directors
et al., p. 4 (June 17, 2011) (“This list is not exhaustive and
no one factor is determinative. ICE offi- cers, agents, and
attorneys should always consider prosecutorial discretion on a
case-by-case basis. The decisions should be based on the totality
of the circumstances, with the goal of conforming to ICE’s
enforcement priorities”). Among those factors is “the agency’s
civil immigration enforcement priorities,” ibid. , which
change from administration to administration. If accepted, the
United States’ pre-emption argument would give the Executive
unprecedented power to invalidate state laws that do not meet with
its approval, even if the state laws are otherwise consistent with
federal statutes and duly promulgated regulations. This argument,
to say the least, is fundamentally at odds with our federal
system.

															B

															It has been suggested that §2(B) will cause
some persons who are lawfully stopped to be detained in violation
of their constitutional rights while a prolonged investigation of
their immigration status is undertaken. But nothing on the face of
the law suggests that it will be enforced in a way that violates
the Fourth Amendment or any other provision of the Constitution.
The law instructs officers to make a “reasonable attempt” to
investigate immigration status, and this language is best
understood as incorporating the Fourth Amendment’s standard of
reasonableness. Indeed, the Arizona Legislature has directed that
§2(B) “shall be implemented in a manner consistent with federal
laws . . . protecting the civil rights of all persons and
respecting the privileges and immunities of United States
citizens.” Ariz. Rev. Stat. Ann. §11–1051(L).

															In the situations that seem most likely to
occur, enforcement of §2(B) will present familiar Fourth Amendment
questions. To take a common situation, suppose that a car is
stopped for speeding, a nonimmigration offense. (Recall that §2(B)
comes into play only where a stop or arrest is made for a
nonimmigration offense.) Suppose also that the officer who makes
the stop subsequently acquires reasonable suspicion to believe that
the driver entered the country illegally, which is a federal crime.
See 8 U. S. C. §1325(a).

															It is well established that state and local
officers generally have authority to make stops and arrests for
violations of federal criminal laws. See, e.g., Miller v. United States , 357
U.S. 301 , 305 (1958); United States v. Di Re , 332 U.S.
581 , 589 (1948). I see no reason why this principle should not
apply to immigration crimes as well. Lower courts have so held.
See, e.g., Estrada v. Rhode Island , 594 F.3d 56, 65
(CA1 2010) (upholding the lawfulness of a detention because the
officer had an objectively reason- able belief that the arrestees
“had committed immigra- tion violations”); United States v. Vasquez-Alvarez , 176 F.3d 1294 , 1296 (CA10 1999) (noting that “state
law-enforcement officers have the general authority to investigate
and make arrests for violations of federal immigration laws”); Gonzales v. Peoria , 722 F.2d 468, 475 (CA9 1983),
overruled on other grounds, Hodgers-Durgin v. de la
Vina , 199 F.3d 1037 (1999) (en banc) (holding that “federal law does
not preclude local enforcement of the criminal provisions” of
federal immigration law). And the United States, consistent with
the position long taken by the Office of Legal Counsel (OLC) in the
Department of Justice, does not contend otherwise. See Brief for
United States 55, n. 33; see also Memorandum from OLC to the
Attorney General (Apr. 3, 2002), App. 268–273; Assistance by State
and Local Police in Apprehending Illegal Aliens, 20 Op. Off. Legal
Counsel 26 (1996).

															More importantly, no federal statute casts doubt
on this authority. To be sure, there are a handful of statutes that
purport to authorize state and local officers to make
immigration-related arrests in certain situations. See, e.g., 8 U. S. C. §1103(a)(10) (providing for the
extension of “any” immigration enforcement authority to state and
local officers in the event of an “actual or imminent mass in- flux
of aliens arriving off the coast”); §1252c(a) (provid- ing
authority to arrest criminal aliens who had illegally reentered the
country but only after consultation with the Federal Government);
§1324(c) (providing authority to make arrests for transporting and
harboring certain aliens). But a grant of federal arrest authority
in some cases does not manifest a clear congressional intent to
displace the States’ police powers in all other cases. Without
more, such an inference is too weak to overcome our presumption
against pre-emption where traditional state police powers are at
stake. Accordingly, in our hypothetical case, the Arizona officer
may arrest the driver for violating §1325(a) if the officer has
probable cause. And if the officer has reasonable suspicion, the
officer may detain the driver, to the extent permitted by the
Fourth Amendment, while the question of illegal entry is
investigated.

															We have held that a detention based on
reasonable suspicion that the detainee committed a particular crime
“can become unlawful if it is prolonged beyond the time reasonably
required to complete that mission.” Illinois v. Caballes , 543 U.S.
405 , 407 (2005). But if during the course of a stop an officer
acquires suspicion that a de- tainee committed a different crime,
the detention may be extended for a reasonable time to verify or
dispel that suspicion. Cf. Muehler v. Mena , 544 U.S.
93 , 101 (2005) (holding that “no additional Fourth Amendment
justification” was required because any questioning concerning
immigration status did not prolong the detention). In our
hypothetical case, therefore, if the officer, after initially
stopping the car for speeding, has a reasonable suspicion that the
driver entered the country illegally, the officer may investigate
for evidence of illegal entry. But the length and nature of this
investigation must remain within the limits set out in our Fourth
Amendment cases. An investigative stop, if prolonged, can become an
arrest and thus require probable cause. See Caballes , supra , at 407. Similarly, if a person is moved from the site
of the stop, probable cause will likely be required. See Hayes v. Florida , 470 U.S.
811 , 816 (1985) (holding that the line be- tween detention and
arrest is crossed “when the police, without probable cause or a
warrant, forcibly remove a person from his home or other place in
which he is entitled to be and transport him to the police station,
where he is detained, although briefly, for investigative
purposes”).

															If properly implemented, §2(B) should not lead
to fed- eral constitutional violations, but there is no denying
that enforcement of §2(B) will multiply the occasions on which
sensitive Fourth Amendment issues will crop up. These civil-liberty
concerns, I take it, are at the heart of most objections to §2(B).
Close and difficult questions will in- evitably arise as to whether
an officer had reasonable suspicion to believe that a person who is
stopped for some other reason entered the country illegally, and
there is a risk that citizens, lawful permanent residents, and
others who are lawfully present in the country will be detained. To
mitigate this risk, Arizona could issue guidance to officers
detailing the circumstances that typically give rise to reasonable
suspicion of unlawful presence. And in the spirit of the
federal-state cooperation that the United States champions, the
Federal Government could share its own guidelines. Arizona could
also provide officers with a nonexclusive list containing forms of
identification sufficient under §2(B) to dispel any suspicion of
unlawful presence. If Arizona accepts licenses from most States as
proof of legal status, the problem of roadside detentions will be
greatly mitigated.[ 1 ] Section 3 I agree that §3 is pre-empted because, like the
Court, I read the opinion in Hines to require that result.
Although there is some ambiguity in Hines , the Court largely
spoke in the language of field pre-emption. The Court explained
that where Congress “has enacted a complete scheme of regulation
and has therein provided a standard for the registration of aliens,
states cannot, inconsistently with the purpose of Congress,
conflict or interfere with, curtail or complement, the federal law,
or enforce additional or auxiliary regulations.” 312 U. S., at
66–67. In finding the Pennsylvania alien-registration law
pre-empted, the Court observed that Congress had “provided a
standard for alien registration in a single integrated and
all-embracing system” and that its intent was “to protect the
personal liberties of law-abiding aliens through one uniform
national registration system.” Id., at 74. If we credit our
holding in Hines that Congress has enacted “a single in-
tegrated and all-embracing system” of alien registration and that
States cannot “complement” that system or “enforce additional or
auxiliary regulations,” id., at 66–67, 74, then Arizona’s
attempt to impose additional, state-law penalties for violations of
federal registration requirements must be invalidated. Section 5(C) While I agree that §3 is pre-empted, I
disagree with the Court’s decision to strike down §5(C). I do so in
large measure because the Court fails to give the same solicitude
to our decision in De Canas , 424 U.S.
351 , as it is willing to give our decision in Hines . In De Canas , the Court upheld against a pre-emption challenge a
state law imposing fines on employers that hired aliens who were
unlawfully present in the United States. The Court explained that
the mere fact that “aliens are the subject of a state statute does
not render it a regulation of immigration.” 424 U. S., at 355.
The Court emphasized instead that “States possess broad authority
under their police powers to regulate the employment relationship
to protect workers within the State.” Id., at 356. In light
of that broad authority, the Court declared that “[o]nly a
demonstration that complete ouster of state power . . . was ‘the
clear and manifest purpose of Congress’ would justify” the
conclusion that “state regulation designed to protect vital state
interests must give way to paramount federal legislation.” Id., at 357 (some internal quotation marks omitted); see
also Bates v. Dow Agrosciences LLC , 544 U.S.
431 , 449 (2005) (“In areas of traditional state regulation,
[the Court] assume[s] that a federal statute has not supplanted
state law unless Congress has made such an intention ‘clear and
manifest’ ” (some internal quotation marks omitted)).

															The Court now tells us that times have changed.
Since De Canas , Congress has enacted “a comprehensive
framework for combating the employment of illegal aliens,” and even
though aliens who seek or obtain unauthorized work are not subject
to criminal sanctions, they can suffer civil penalties. Ante, at 12–13 (internal quotation marks omitted).
Undoubtedly, federal regulation in this area is more pervasive
today. But our task remains unchanged: to determine whether the
federal scheme discloses a clear and manifest congressional intent
to displace state law.

															The Court gives short shrift to our presumption against pre-emption. Having no express statement of
congressional intent to support its analysis, the Court infers from
stale legislative history and from the comprehensiveness of the
federal scheme that “Congress made a deliberate choice not to
impose criminal penalties on aliens who seek, or engage in,
unauthorized employment.” Ante, at 13. Because §5(C) imposes
such penalties, the Court concludes that it stands as an obstacle
to the method of enforcement chosen by Congress. Ante, at
15.

															The one thing that is clear from the federal
scheme is that Congress chose not to impose federal criminal
penalties on aliens who seek or obtain unauthorized work. But that
does not mean that Congress also chose to pre-empt state criminal penalties. The inference is plausible, but far from
necessary. As we have said before, the “decision not to adopt a
regulation” is not “the functional equivalent of a regulation
prohibiting all States and their political subdivisions from
adopting such a regulation.” Sprietsma v. Mercury
Marine , 537 U.S.
51 , 65 (2002). With any statutory scheme, Congress chooses to
do some things and not others. If that alone were enough to
demonstrate pre-emptive intent, there would be little left over for
the States to regulate, especially now that federal authority
reaches so far and wide. States would occupy tiny islands in a sea
of federal power. This explains why state laws implicating
traditional state powers are not pre-empted unless there is a
“clear and manifest” congressional intention to do so.

															Not only is there little evidence that Congress
intended to pre-empt state laws like §5(C), there is some evidence
that Congress intended the opposite result. In making it unlawful
for employers to hire unauthorized aliens, see 8 U. S. C.
§1324a(a), Congress made it clear that “any State or local law
imposing civil or criminal sanctions (other than through licensing
and similar laws)” upon employers was pre-empted, §1324a(h)(2).
Noticeably absent is any similar directive pre-empting state or
local laws targeting aliens who seek or obtain unauthorized
employment. Given that Congress expressly pre-empted certain state
and local laws pertaining to employers but remained silent about
laws pertaining to employees, one could infer that Congress
intended to preserve state and local authority to regulate the
employee side of the equation. At the very least, it raises serious
doubts about whether Congress intended to pre-empt such
authority.

															The Court dismisses any inferences that might be
drawn from the express pre-emption provision. See ante, at
14. But even though the existence of that provision “does not bar the ordinary working of conflict pre-emption
principles” or impose a “ ‘special burden’ ” against
pre-emption, Geier v. American Honda Motor Co. , 529 U.S.
861 , 869–870 (2000), it is still probative of congressional
intent. And it is the intent of Congress that is the “ultimate
touchstone.” Retail Clerks v. Schermerhorn , 375 U.S.
96 , 103 (1963).

															The Court infers from Congress’ decision not to
impose federal criminal penalties that Congress intended to
pre-empt state criminal penalties. But given that the
express pre-emption provision covers only state and local laws
regulating employers , one could just as well infer that
Congress did not intend to pre-empt state or local laws aimed at
alien employees who unlawfully seek or obtain work. Surely
Congress’ decision not to extend its express pre-emption provision
to state or local laws like §5(C) is more probative of its intent
on the subject of pre-emption than its decision not to impose
federal criminal penalties for unauthorized work. In any event, the
point I wish to emphasize is that inferences can be drawn either
way. There are no necessary inferences that point decisively for or
against pre-emption. Therefore, if we take seriously that state
employment regulation is a traditional state concern and can be
pre-empted only on a showing of “clear and manifest” congressional
intent as required by De Canas , then §5(C) must survive.
“Our precedents establish that a high threshold must be met if a
state law is to be pre-empted for conflicting with the purposes of
a fed- eral Act.” Chamber of Commerce of United States of
America v. Whiting , 563 U. S. ___, ___ (2011)
(plurality opinion) (slip op., at 22) (internal quotation marks
omitted). I do not believe the United States has surmounted that
barrier here. Section 6 I also disagree with the Court’s decision that
§6 is pre-empted. This provision adds little to the authority that
Arizona officers already possess, and whatever additional authority
it confers is consistent with federal law. Section 6 amended an
Arizona statute that authorizes warrantless arrests. See Ariz. Rev.
Stat. §13–3883 (West 2010). Before §6 was added, that statute
already permitted arrests without a warrant for felonies,
misdemeanors committed in the arresting officer’s presence, petty
offenses, and certain traffic-related criminal violations. See
§§13–3883(A)(1)–(4). Largely duplicating the authority already
conferred by these prior subsections, §6 added a new subsection,
§13–3883(A)(5) (West Supp. 2011), that authorizes officers to make
warrantless arrests on probable cause that the arrestee has
committed a “public offense” for which the arrestee is removable
from the United States. A “public offense” is defined as conduct
that is punishable by imprisonment or a fine according to the law
of the State where the conduct occurred and that would be
punishable under Arizona law had the conduct occurred in Arizona.
See §13–105(27).

															In what way, if any, does §6 enlarge the arrest
authority of Arizona officers? It has been suggested that §6
confers new authority in the following three circumstances: (1)
where the arrestee committed but has not been charged with
committing an offense in another State; (2) where the officer has
probable cause to believe the arrestee committed an offense for
which he was previously arrested but not prosecuted; and (3) where
the arrestee committed but has already served the sentence for a
removable offense. 641 F.3d 359, 361 (CA9 2011). These are
exceedingly narrow categories, involving circumstances that will
rarely arise. But such cases are possible, and therefore we must
decide whether there are circumstances under which fed- eral law
precludes a state officer from making an arrest based on probable
cause that the arrestee committed a removable offense.

															A

															The idea that state and local officers may
carry out arrests in the service of federal law is not
unprecedented. As previously noted, our cases establish that state
and local officers may make warrantless arrests for violations of
federal law and that “in the absence of an applicable federal
statute the law of the state where an arrest without warrant takes
place determines its validity.” Di Re , 332 U. S., at
589; see also Miller, 357 U. S., at 305 (stating that,
where a state officer makes an arrest based on fed- eral law, “the
lawfulness of the arrest without warrant is to be determined by
reference to state law”). Therefore, given the premise, which I
understand both the United States and the Court to accept, that
state and local officers do have inherent authority to make arrests
in aid of fed- eral law, we must ask whether Congress has done
anything to curtail or pre-empt that authority in this particular
case.

															Neither the United States nor the Court goes so
far as to say that state and local officers have no power to arrest
criminal aliens based on their removability. To do so would fly in
the face of 8 U. S. C. §1357(g)(10). Under
§§1357(g)(1)–(9), the Federal Government may enter into formal
agreements with States and municipalities under which their
officers may perform certain duties of a fed- eral immigration
officer. But §1357(g)(10)(B) makes clear that States and
municipalities need not enter into those agreements “otherwise to
cooperate . . . in the identification, apprehension, detention, or
removal of aliens not lawfully present in the United States.” It
goes without saying that state and local officers could not provide
meaningful cooperation in the apprehension, detention, and ultimate
removal of criminal aliens without some power to make arrests.

															Although §1357(g)(10) contemplates state and
local authority to apprehend criminal aliens for the purpose of
removal, the Court rejects out of hand any possibility that
officers could exercise that authority without federal direction.
Despite acknowledging that there is “ambiguity as to what
constitutes cooperation,” the Court says that “no coherent
understanding of the term would incorporate the unilateral decision
of state officers to arrest an alien for being removable absent any
request, approval, or other instruction from the Federal
Government.” Ante, at 18. The Court adopts an unnecessarily
stunted view of cooperation. No one would say that a state or local
officer has failed to cooperate by making an on-the-spot arrest to
enforce federal law. Unsolicited aid is not necessarily
uncooperative.

															To be sure, were an officer to persist in making
an arrest that the officer knows is unwanted, such conduct would
not count as cooperation. But nothing in the relevant federal
statutes suggests that Congress does not want aliens who have
committed removable offenses to be arrested.[ 2 ] To the contrary, §1226(c)(1) commands that the
Executive “shall take into custody any alien” who is deportable for
having committed a specified offense. And §1226(c)(2) substantially
limits the circumstances under which the Executive has discretion
to release aliens held in custody under paragraph (1). So if an
officer arrests an alien who is removable for having committed one
of the crimes listed in §1226(c)(1), the Federal Government is
obligated to take the alien into custody.

															That Congress generally requires the Executive
to take custody of criminal aliens casts considerable doubt on the
Court’s concern that §6 is an obstacle to the Federal Government’s
exercise of discretion. The Court claims that the authority
conferred by §6 “could be exercised without any input from the
Federal Government about whether an arrest is warranted in a
particular case” and that this “would allow the State to achieve
its own immigration policy,” resulting in the “unnecessary
harassment of some aliens . . . whom federal officials determine
should not be removed.” Ante, at 17. But §1226(c)(1) belies
the Court’s fear. In many, if not most, cases involving aliens who
are removable for having committed criminal offenses, Congress has
left the Executive no discretion but to take the alien into
custody. State and local officers do not frus- trate the removal
process by arresting criminal aliens. The Executive retains
complete discretion over whether those aliens are ultimately
removed. And once the Fed- eral Government makes a determination
that a particular criminal alien will not be removed, then Arizona
officers are presumably no longer authorized under §6 to arrest the
alien.

															To be sure, not all offenses for which officers
have authority to arrest under §6 are covered by §1226(c)(1). As
for aliens who have committed those offenses, Congress has given
the Executive discretion under §1226(a) over whether to arrest and
detain them pending a decision on removal. But the mere fact that
the Executive has enforcement discretion cannot mean that the
exercise of state police powers in support of federal law is
automatically pre-empted. If that were true, then state and local
officers could never make arrests to enforce any federal statute
because the Executive always has at least some general discretion
over the enforcement of federal law as a practical matter. But even
assuming that the express statutory grant of discretion in §1226(a)
somehow indicates a congressional desire to pre-empt unilateral
state and local authority to arrest criminal aliens covered by that
provision, §6 is not pre-empted on its face given its substantial
overlap with §1226(c)(1).

															It bears emphasizing that §6 does not mandate
the warrantless apprehension of all aliens who have committed
crimes for which they are removable. Instead, it only grants state
and local officers permission to make such arrests. The trouble
with this premature, facial challenge is that it affords Arizona no
opportunity to implement its law in a way that would avoid any
potential conflicts with federal law. For example, Arizona could
promulgate guidelines or regulations limiting the arrest authority
conferred by §6 to the crimes specified in §1226(c)(1). And to the
extent §1226(c)(1) is unclear about which exact crimes are
covered,[ 3 ] Arizona could go
even further and identify specific crimes for which there is no
doubt an alien would be removable. The point is that there are
plenty of permissible applications of §6, and the Court should not
invalidate the statute at this point without at least some
indication that Arizona has implemented it in a manner at odds with
Congress’ clear and manifest intent. We have said that a facial
challenge to a statute is “the most difficult challenge to mount
successfully” because “the challenger must establish that no set of
circumstances exists under which the [statute] would be valid.” United States v. Salerno , 481
U.S. 739 , 745 (1987); see also Anderson v. Edwards , 514 U.S.
143 , 155, n. 6 (1995) (applying the Salerno standard in a pre-emption case). As to §6, I do not believe the
United States has carried that heavy burden.

															B

															Finally, the Court tells us that §6 conflicts
with federal law because it provides state and local officers with
“even greater authority to arrest aliens on the basis of possible
removability than Congress has given to trained federal immigration
officers.” Ante, at 16–17. The Court points to 8
U. S. C. §1357(a)(2), which empowers “authorized” offi-
cers and employees of ICE to make arrests without a fed- eral
warrant if “the alien so arrested is in the United States in
violation of any [immigration] law or regulation and is likely to
escape before a warrant can be obtained for his arrest.” Because §6
would allow Arizona officers to make arrests “regardless of whether
a federal warrant has issued or the alien is likely to escape,” ante, at 17, the Court concludes that §6 is an obstacle to
the accomplishment of Congress’ objectives. But §6 is an obstacle
only to the extent it conflicts with Congress’ clear and manifest
intent to preclude state and local officers from making arrests
except where a federal warrant has issued or the arrestee is likely
to escape. By granting warrantless arrest authority to federal
officers , Congress has not manifested an unmistakable intent to
strip state and local officers of their warrantless arrest
authority under state law.

															Likewise, limitations on federal arrest
authority do not mean that the arrest authority of state and local
officers must be similarly limited. Our opinion in Miller, 357 U.S.
301 , is instructive. In that case, a District of Columbia
officer, accompanied by a federal officer, made an arrest based on
a suspected federal narcotics offense. Id., at 303–304. The
federal officer did not have statutory authorization to arrest
without a warrant, but the local officer did. Id., at 305.
We held that District of Columbia law dictated the lawfulness of
the arrest. Id., at 305–306. Where a state or local officer
makes a warrantless arrest to enforce federal law, we said that
“the lawfulness of the arrest without warrant is to be determined
by reference to state law.” Id., at 305. Under §6, an
Arizona officer may be authorized to make an arrest that a federal
officer may not be authorized to make under §1357(a)(2). As Miller makes clear, that fact alone does not render arrests
by state or local officers pursuant to §6 unlawful. Nor does it
manifest a clear congressional intent to displace the exercise of
state police powers that are brought to bear in aid of federal
law. Notes 1 When the Real ID Act
takes effect, the Federal Government will no longer accept state
forms of identification that fail to meet certain federal
requirements. §202(a)(1), 119Stat. 312. One requirement is that any
identification be issued only on proof that the applicantis
lawfully present in the United States. §202(c)(2)(B), id., at 313. I anticipate that most, if not all, States will eventually
issue forms of identification that suffice to establish lawful
presence under §2(B). 2 That goes for the
Executive Branch as well, which has made the apprehension and
removal of criminal aliens a priority. See App. 108. 3 I readily admit that it
can be difficult to determine whether aparticular conviction will
necessarily make an alien removable. See Padilla v. Kentucky , 559 U. S. ___, ___ (2010) (Alito, J.,
concurring in judgment) (slip op., at 4).

Summary:
The Supreme Court of the United States reviewed Arizona's Support Our Law Enforcement and Safe Neighborhoods Act, also known as S.B. 1070, which aimed to address the state's large number of illegal aliens. The Court examined four provisions of the law, including the creation of new state offenses for failing to comply with federal alien-registration requirements and for unauthorized aliens seeking work. The Court also looked at provisions granting state and local law enforcement officers authority to arrest individuals suspected of being removable from the country and requiring officers to verify immigration status during stops, detentions, or arrests.

The Court's opinion, delivered by Justice Kennedy, concluded that federal law preempts and renders invalid certain provisions of Arizona's law. Specifically, the Court found that Section 3, which made failure to comply with federal alien-registration requirements a state misdemeanor, and Section 5(C), which made it a misdemeanor for unauthorized aliens to seek or engage in work, were preempted by federal law. On the other hand, the Court upheld Section 6, authorizing officers to arrest without a warrant individuals suspected of being removable, and Section 2(B), requiring officers to verify immigration status, as not posing an obstacle to federal law.

The Court's decision considered the balance between federal and state powers in immigration enforcement, with Justice Kennedy emphasizing that state laws could aid in the enforcement of federal immigration standards. However, the Court struck down provisions that conflicted with or posed an obstacle to Congress's objectives in enacting federal immigration laws.