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															SUPREME COURT OF THE UNITED STATES

															_________________

															Nos. 12–1146, 12–1248,
12–1254, 12–1268, 12–1269, and 12–1272

															_________________

															UTILITY AIR REGULATORY
GROUP,PETITIONER

															12–1146      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															AMERICAN CHEMISTRY COUNCIL,
et al.,PETITIONERS

															12–1248      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															ENERGY-INTENSIVE MANUFACTURERS
WORKINGGROUP ON GREENHOUSE GAS REGULATION,et al.,
PETITIONERS

															12–1254      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															SOUTHEASTERN LEGAL FOUNDATION,
INC.,et al., PETITIONERS

															12–1268      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															TEXAS, et al., PETITIONERS

															12–1269      v.

															ENVIRONMENTAL PROTECTION AGENCY, et al.;
and

															CHAMBER OF COMMERCE OF THE UNITEDSTATES,
et al., PETITIONERS

															12–1272      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															on writs of certiorari to the united states
court ofappeals for the district of columbia circuit

															[June 23, 2014]

															     Justice Scalia
announced the judgment of the Court and delivered the opinion of
the Court with respect to Parts I and II.

															     Acting pursuant to the
Clean Air Act, 69Stat. 322, as amended, 42 U. S. C.
§§7401–7671q, the Environmental Protection Agency
recently set standards for emissions of “greenhouse
gases” (substances it believes contribute to “global
climate change”) from new motor vehicles. We must decide
whether it was permissible for EPA to determine that its
motor-vehicle greenhouse-gas regulations automatically triggered
permitting requirements under the Act for stationary sources that
emit greenhouse gases.

															I. Background

															A. Stationary-Source Permitting

															     The Clean Air Act
regulates pollution-generating emissions from both stationary
sources, such as factories and powerplants, and moving sources,
such as cars, trucks, and aircraft. This litigation concerns
permitting obligations imposed on stationary sources under Titles I
and V of the Act.

															     Title I charges EPA
with formulating national ambient air quality standards (NAAQS) for
air pollutants. §§7408–7409. To date, EPA has
issued NAAQS for six pollutants: sulfur dioxide, particulate
matter, nitrogen dioxide, carbon monoxide, ozone, and lead. Clean
Air Act Handbook 125 (J. Domike & A. Zacaroli eds., 3d ed.
2011); see generally 40 CFR pt. 50 (2013). States have primary
responsibility for implementing the NAAQS by developing
“State implementation plans.” 42 U. S. C.
§7410. A State must designate every area within its borders as
“attainment,” “nonattainment,” or
“unclassifiable” with respect to each NAAQS,
§7407(d), and the State’s implementation plan must
include permitting programs for stationary sources that vary
according to the classification of the area where the source is or
is proposed to be located. §7410(a)(2)(C), (I).

															     Stationary sources in
areas designated attainment or unclassifiable are subject to the
Act’s provisions relating to “Prevention of Significant
Deterioration” (PSD). §§7470–7492. EPA
interprets the PSD provisions to apply to sources located in areas
that are designated attainment or unclassifiable for any NAAQS
pollutant, regardless of whether the source emits that specific
pollutant. Since the inception of the PSD program, every area of
the country has been designated attainment or unclassifiable for at
least one NAAQS pollutant; thus, on EPA’s view, all
stationary sources are potentially subject to PSD review.

															     It is unlawful to
construct or modify a “major emitting facility” in
“any area to which [the PSD program] applies” without
first obtaining a permit. §§7475(a)(1), 7479(2)(C). To
qualify for a permit, the facility must not cause or contribute to
the violation of any applicable air-quality standard,
§7475(a)(3), and it must comply with emissions limitations
that reflect the “best available control technology”
(or BACT) for “each pollutant subject to regulation
under” the Act. §7475(a)(4). The Act defines a
“major emitting facility” as any stationary source with
the potential to emit 250 tons per year of “any air
pollutant” (or 100 tons per year for certain types of
sources). §7479(1). It defines “modification” as a
physical or operational change that causes the facility to emit
more of “any air pollutant.” §7411(a)(4).[ 1 ]

															     In addition to the PSD
permitting requirements for construction and modification, Title V
of the Act makes it unlawful to operate any “major
source,” wherever located, without a comprehensive operating
permit. §7661a(a). Unlike the PSD program, Title V generally
does not impose any substantive pollution-control requirements.
Instead, it is designed to facilitate compliance and enforcement by
consolidating into a single document all of a facility’s
obligations under the Act. The permit must include all
“emissions limitations and standards” that apply to the
source, as well as associated inspection, monitoring, and reporting
requirements. §7661c(a)–(c). Title V defines a
“major source” by reference to the Act-wide definition
of “major stationary source,” which in turn means any
stationary source with the potential to emit 100 tons per year of
“any air pollutant.” §§7661(2)(B),
7602( j).

															B. EPA’s Greenhouse-Gas Regulations

															     In 2007, the Court
held that Title II of the Act “authorize[d] EPA to regulate
greenhouse gas emissions from new motor vehicles” if the
Agency “form[ed] a ‘judgment’ that such emissions
contribute to climate change.” Massachusetts v. EPA, 549
U. S. 497 (quoting §7521(a)(1)). In response to that
decision, EPA embarked on a course of regulation resulting in
“the single largest expansion in the scope of the [Act] in
its history.” Clean Air Act Handbook, at xxi.

															     EPA first asked the
public, in a notice of proposed rulemaking, to comment on how the
Agency should respond to Massachusetts. In doing so, it explained
that regulating greenhouse-gas emissions from motor vehicles could
have far-reaching consequences for stationary sources. Under
EPA’s view, once greenhouse gases became regulated under any
part of the Act, the PSD and Title V permitting requirements would
apply to all stationary sources with the potential to emit
greenhouse gases in excess of the statutory thresholds: 100 tons
per year under Title V, and 100 or 250 tons per year under the PSD
program depending on the type of source. 73 Fed. Reg. 44420, 44498,
44511 (2008). Because greenhouse-gas emissions tend to be
“orders of magnitude greater” than emissions of
conventional pollutants, EPA projected that numerous small sources
not previously regulated under the Act would be swept into the PSD
program and Title V, including “smaller industrial
sources,” “large office and residential build-ings,
hotels, large retail establishments, and similar facilities.”
Id., at 44498–44499. The Agency warned that this would
constitute an “unprecedented expansion of EPA authority that
would have a profound effect on virtually every sector of the
economy and touch every household in the land,” yet still be
“relatively ineffective at reducing greenhouse gas
concentrations.” Id., at 44355.[ 2 ]

															     In 2009, EPA announced
its determination regarding the danger posed by motor-vehicle
greenhouse-gas emissions. EPA found that greenhouse-gas emissions
from new motor vehicles contribute to elevated atmospheric
concentrations of greenhouse gases, which endanger public health
and welfare by fostering global “climate change.” 74
Fed. Reg. 66523, 66537 (hereinafter Endangerment Finding). It
denominated a “single air pollutant” the
“combined mix” of six greenhouse gases that it
identified as “the root cause of human-induced climate
change”: carbon dioxide, methane, nitrous oxide,
hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. Id.,
at 66516, 66537. A source’s greenhouse-gas emissions would be
measured in “carbon dioxide equivalent units” (CO2e),
which would be calculated based on each gas’s “global
warming potential.” Id., at 66499, n. 4.

															     Next, EPA issued its
“final decision” regarding the prospect that
motor-vehicle greenhouse-gas standards would trigger
stationary-source permitting requirements. 75 Fed. Reg. 17004
(2010) (hereinafter Triggering Rule). EPA announced that beginning
on the effective date of its greenhouse-gas standards for motor
vehicles, stationary sources would be subject to the PSD program
and Title V on the basis of their potential to emit greenhouse
gases. As expected, EPA in short order promulgated greenhouse-gas
emission standards for passenger cars, light-duty trucks, and
medium-duty passenger vehicles to take effect on January 2, 2011.
75 Fed. Reg. 25324 (hereinafter Tailpipe Rule).

															     EPA then announced
steps it was taking to “tailor” the PSD program and
Title V to greenhouse gases. 75 Fed. Reg. 31514 (hereinafter
Tailoring Rule). Those steps were necessary, it said, because the
PSD program and Title V were designed to regulate “a
relatively small number of large industrial sources,” and
requiring permits for all sources with greenhouse-gas emissions
above the statu-tory thresholds would radically expand those
programs, making them both unadministrable and
“unrecognizable to the Congress that designed” them.
Id., at 31555, 31562. EPA nonetheless rejected calls to exclude
greenhouse gases entirely from those programs, asserting that the
Act is not “ambiguous with respect to the need to cover
[greenhouse-gas] sources under either the PSD or title V
program.” Id., at 31548, n. 31. Instead, EPA adopted a
“phase-in approach” that it said would “appl[y]
PSD and title V at threshold levels that are as close to the
statutory levels as possible, and do so as quickly as possible, at
least to a certain point.” Id., at 31523.

															     The phase-in, EPA said,
would consist of at least three steps. During Step 1, from January
2 through June 30, 2011, no source would become newly subject to
the PSD program or Title V solely on the basis of its
greenhouse-gas emissions; however, sources required to obtain
permits anyway because of their emission of conventional pollutants
(so-called “anyway” sources) would need to comply with
BACT for greenhouse gases if they emitted those gases in
significant amounts, defined as at least 75,000 tons per year CO2e.
Ibid. During Step 2, from July 1, 2011, through June 30, 2012,
sources with the potential to emit at least 100,000 tons per year
CO2e of greenhouse gases would be subject to PSD and Title V
permitting for their construction and operation and to PSD
permitting for modifications that would increase their
greenhouse-gas emissions by at least 75,000 tons per year CO2e.
Id., at 31523–31524.[ 3 ]
At Step 3, beginning on July 1, 2013, EPA said it might (or might
not) further reduce the permitting thresholds (though not below
50,000 tons per year CO2e), and it might (or might not) establish
permanent exemptions for some sources. Id., at 31524. Beyond Step
3, EPA promised to complete another round of rulemaking by April
30, 2016, in which it would “take further action to address
small sources,” which might (or might not) include
establishing permanent exemptions. Id., at 31525.

															     EPA codified Steps 1
and 2 at 40 CFR §§51.166(b)(48) and 52.21(b)(49) for PSD
and at §§70.2 and 71.2 for Title V, and it codified its
commitments regarding Step 3 and beyond at §§52.22,
70.12, and 71.13. See Tailoring Rule 31606–31608. After the
decision below, EPA issued its final Step 3 rule, in which it
decided not to lower the thresholds it had established at Step 2
until at least 2016. 77 Fed. Reg. 41051 (2012).

															C. Decision Below

															     Numerous parties,
including several States, filed petitions for review in the
D. C. Circuit under 42 U. S. C. §7607(b),
challenging EPA’s greenhouse-gas-related actions. The Court
of Appeals dismissed some of the petitions for lack of jurisdiction
and denied the remainder. Coalition for Responsible Regulation,
Inc. v. EPA, 684 F. 3d 102 (2012) (per curiam). First, it
upheld the Endangerment Finding and Tailpipe Rule. Id., at 119,
126. Next, it held that EPA’s interpretation of the PSD
permitting requirement as applying to “any regulated air
pollutant,” including greenhouse gases, was “compelled
by the statute.” Id., at 133–134. The court also found
it “crystal clear that PSD permittees must install BACT for
greenhouse gases.” Id., at 137. Because it deemed
petitioners’ arguments about the PSD program insufficiently
applicable to Title V, it held they had “forfeited any
challenges to EPA’s greenhouse gas-inclusive interpretation
of Title V.” Id., at 136. Finally, it held that petitioners
were without Article III standing to challenge EPA’s efforts
to limit the reach of the PSD program and Title V through the
Triggering and Tailoring Rules. Id., at 146. The court denied
rehearing en banc, with Judges Brown and Kavanaugh each dissenting.
No. 09–1322 etc. (Dec. 20, 2012), App. 139, 2012 WL
6621785.

															     We granted six
petitions for certiorari but agreed to decide only one question:
“ ‘Whether EPA permissibly determined that its
regulation of greenhouse gas emissions from new motor vehicles
triggered permitting requirements under the Clean Air Act for
stationary sources that emit greenhouse gases.’ ”
571 U. S. ____ (2013).

															II. Analysis

															     This litigation
presents two distinct challenges to EPA’s stance on
greenhouse-gas permitting for stationary sources. First, we must
decide whether EPA permissibly determined that a source may be
subject to the PSD and Title V permitting requirements on the sole
basis of the source’s potential to emit greenhouse gases.
Second, we must decide whether EPA permissibly determined that a
source already subject to the PSD program because of its emission
of conventional pollutants (an “anyway” source) may be
required to limit its greenhouse-gas emissions by employing the
“best available control technology” for greenhouse
gases. The Solicitor General joins issue on both points but
evidently regards the second as more important; he informs us that
“anyway” sources account for roughly 83% of American
stationary-source greenhouse-gas emissions, compared to just 3% for
the additional, non-“anyway” sources EPA sought to
regulate at Steps 2 and 3 of the Tailoring Rule. Tr. of Oral Arg.
52.

															     We review EPA’s
interpretations of the Clean Air Act using the standard set forth
in Chevron U. S. A. Inc. v. Natural Resources Defense
Council, Inc., 467 U. S. 837 –843 (1984). Under Chevron,
we presume that when an agency-administered statute is ambiguous
with respect to what it prescribes, Congress has empowered the
agency to resolve the ambiguity. The question for a reviewing court
is whether in doing so the agency has acted reasonably and thus has
“stayed within the bounds of its statutory authority.”
Arlington v. FCC, 569 U. S. ___, ___ (2013) (slip op., at 5)
(emphasis deleted).

															A. The PSD and Title V Triggers

															     We first decide
whether EPA permissibly interpreted the statute to provide that a
source may be required to obtain a PSD or Title V permit on the
sole basis of its potential greenhouse-gas emissions.

															1

															     EPA thought its
conclusion that a source’s greenhouse-gas emissions may
necessitate a PSD or Title V permit followed from the Act’s
unambiguous language. The Court of Appeals agreed and held that the
statute “compelled” EPA’s interpretation. 684
F. 3d, at 134. We disagree. The statute compelled EPA’s
greenhouse-gas-inclusive interpretation with respect to neither the
PSD program nor Title V.[ 4 ]

															     The Court of Appeals
reasoned by way of a flawed syllogism: Under Massachusetts, the
general, Act-wide definition of “air pollutant”
includes greenhouse gases; the Act requires permits for major
emitters of “any air pollutant”; therefore, the Act
requires permits for major emitters of greenhouse gases. The
conclusion follows from the premises only if the air pollutants
referred to in the permit-requiring provisions (the minor premise)
are the same air pollutants encompassed by the Act-wide definition
as interpreted in Massachusetts (the major premise). Yet no
one—least of all EPA—endorses that proposition, and it
is obviously untenable.

															     The Act-wide definition
says that an air pollutant is “any air pollution agent or
combination of such agents, including any physical, chemical,
biological, [or] radioactive . . . substance or matter
which is emitted into or otherwise enters the ambient air.”
§7602(g). In Massachusetts, the Court held that the Act-wide
definition includes greenhouse gases because it is
all-encompassing; it “embraces all airborne compounds of
whatever stripe.” 549 U. S., at 529. But where the term
“air pollutant” appears in the Act’s operative
provisions, EPA has routinely given it a narrower,
context-appropriate meaning.

															     That is certainly true
of the provisions that require PSD and Title V permitting for major
emitters of “any air pollutant.” Since 1978,
EPA’s regulations have interpreted “air
pollutant” in the PSD permitting trigger as limited to
regulated air pollutants, 43 Fed. Reg. 26403, codified, as amended,
40 CFR §52.21(b)(1)–(2), (50)—a class much
narrower than Massachusetts’ “all airborne compounds of
whatever stripe,” 549 U. S., at 529. And since 1993 EPA
has informally taken the same position with regard to the Title V
permitting trigger, a position the Agency ultimately incorporated
into some of the regulations at issue here. See Memorandum from
Lydia N. Wegman, Deputy Director, Office of Air Quality Planning
and Standards, to Air Division Director, Regions I–X,
pp. 4–5 (Apr. 26, 1993); Tailoring Rule
31607–31608 (amending 40 CFR §§70.2, 71.2). Those
interpretations were appropriate: It is plain as day that the Act
does not envision an elaborate, burdensome permitting process for
major emitters of steam, oxygen, or other harmless airborne
substances. It takes some cheek for EPA to insist that it cannot
possibly give “air pollutant” a reasonable,
context-appropriate meaning in the PSD and Title V contexts when it
has been doing precisely that for decades.

															     Nor are those the only
places in the Act where EPA has inferred from statutory context
that a generic reference to air pollutants does not encompass every
substance falling within the Act-wide definition. Other examples
abound:

															The Act authorizes EPA to enforce new source
performance standards (NSPS) against a pre-existing source if,
after promulgation of the standards, the source undergoes a
physical or operational change that increases its emission of
“any air pollutant.” §7411(a)(2), (4), (b)(1)(B).
EPA interprets that provision as limited to air pollutants for
which EPA has promulgated new source performance standards. 36 Fed.
Reg. 24877 (1971), codified, as amended, 40 CFR §60.2; 40 Fed.
Reg. 58419 (1975), codified, as amended, 40 CFR §60.14(a).

															The Act requires a permit for the construction
or operation in a nonattainment area of a source with the potential
to emit 100 tons per year of “any air pollutant.”
§§7502(c)(5), 7602(j). EPA interprets that provision as
limited to pollutants for which the area is designated
nonattainment. 45 Fed. Reg. 52745 (1980), promulgating 40 CFR
§51.18(j)(2), as amended, §51.165(a)(2).

															The Act directs EPA to require “enhanced
monitoring and submission of compliance certifications” for
any source with the potential to emit 100 tons per year of
“any air pollutant.” §§7414(a)(3), 7602(j).
EPA interprets that provision as limited to regulated pollutants.
62 Fed. Reg. 54941 (1997), codifiedat 40 CFR §§64.1,
64.2.

															The Act requires certain sources of air
pollutants that interfere with visibility to undergo retrofitting
if they have the potential to emit 250 tons per year of “any
pollutant.” §7491(b)(2)(A), (g)(7). EPA interprets that
provision as limited to visibility-impairing air pollutants. 70
Fed. Reg. 39160 (2005), codified at 40 CFR pt. 51, App. Y,
§II.A.3.

															Although these limitations are nowhere to be
found in the Act-wide definition, in each instance EPA has
concluded—as it has in the PSD and Title V context—that
the statute is not using “air pollutant” in
Massachusetts’ broad sense to mean any airborne substance
whatsoever.

															     Massachusetts did not
invalidate all these longstanding constructions. That case did not
hold that EPA must always regulate greenhouse gases as an
“air pollutant” everywhere that term appears in the
statute, but only that EPA must “ground its reasons for
action or inaction in the statute,” 549 U. S., at 535
(emphasis added), rather than on “reasoning divorced from the
statutory text,” id., at 532. EPA’s inaction with
regard to Title II was not sufficiently grounded in the statute,
the Court said, in part because nothing in the Act suggested that
regulating greenhouse gases under that Title would conflict with
the statutory design. Title II would not compel EPA to regulate in
any way that would be “extreme,”
“counterintuitive,” or contrary to
“ ‘common sense.’ ” Id., at 531.
At most, it would require EPA to take the modest step of adding
greenhouse-gas standards to the roster of new-motor-vehicle
emission regulations. Ibid.

															     Massachusetts does not
strip EPA of authority to exclude greenhouse gases from the class
of regulable air pollutants under other parts of the Act where
their inclusion would be inconsistent with the statutory scheme.
The Act-wide definition to which the Court gave a
“sweeping” and “capacious” interpretation,
id., at 528, 532, is not a command to regulate, but a description
of the universe of substances EPA may consider regulating under the
Act’s operative provisions. Massachusetts does not foreclose
the Agency’s use of statutory context to infer that certain
of the Act’s provisions use “air pollutant” to
denote not every conceivable airborne substance, but only those
that may sensibly be encompassed within the particular regulatory
program. As certain amici felicitously put it, while Massachusetts
“rejected EPA’s categorical contention that greenhouse
gases could not be ‘air pollutants’ for any purposes of
the Act,” it did not “embrace EPA’s current,
equally categorical position that greenhouse gases must be air
pollutants for all purposes” regardless of the statutory
context. Brief for Administrative Law Professors et al. as
Amici Curiae 17.[ 5 ]

															     To be sure,
Congress’s profligate use of “air pollutant”
where what is meant is obviously narrower than the Act-wide
definition is not conducive to clarity. One ordinarily assumes
“ ‘that identical words used in different parts of
the same act are intended to have the same
meaning.’ ” Environmental Defense v. Duke Energy
Corp., 549 U. S. 561, 574 (2007) . In this respect (as in
countless others), the Act is far from a chef d’oeuvre of
legislative draftsmanship. But we, and EPA, must do our best,
bearing in mind the “ ‘fundamental canon of
statutory construction that the words of a statute must be read in
their context and with a view to their place in the overall
statutory scheme.’ ” FDA v. Brown & Williamson
Tobacco Corp., 529 U. S. 120, 133 (2000) . As we reiterated
the same day we decided Massachusetts, the presumption of
consistent usage “ ‘readily
yields’ ” to context, and a statutory
term—even one defined in the statute—“may take on
distinct characters from association with distinct statutory
objects calling for different implementation strategies.”
Duke Energy, supra, at 574.

															     We need not, and do
not, pass on the validity of all the limiting constructions EPA has
given the term “air pollutant” throughout the Act. We
merely observe that taken together, they belie EPA’s rigid
insistence that when interpreting the PSD and Title V permitting
requirements it is bound by the Act-wide definition’s
inclusion of greenhouse gases, no matter how incompatible that
inclusion is with those programs’ regulatory structure.

															     In sum, there is no
insuperable textual barrier to EPA’s interpreting “any
air pollutant” in the permitting triggers of PSD and Title V
to encompass only pollutants emitted in quantities that enable them
to be sensibly regulated at the statutory thresholds, and to
exclude those atypical pollutants that, like greenhouse gases, are
emitted in such vast quantities that their inclusion would
radically transform those programs and render them unworkable as
written.[ 6 ]

															2

															     Having determined
that EPA was mistaken in thinking the Act compelled a
greenhouse-gas-inclusive interpretation of the PSD and Title V
triggers, we next consider the Agency’s alternative position
that its interpretation was justified as an exercise of its
“discretion” to adopt “a reasonable construction
of the statute.” Tailoring Rule 31517. We conclude that
EPA’s interpretation is not permissible.

															     Even under
Chevron’s deferential framework, agencies must operate
“within the bounds of reasonable interpretation.”
Arlington, 569 U. S., at ___ (slip op., at 5). And reasonable
statutory interpretation must account for both “the specific
context in which . . . language is used” and
“the broader context of the statute as a whole.”
Robinson v. Shell Oil Co., 519 U. S. 337, 341 (1997) . A
statutory “provision that may seem ambiguous in isolation is
often clarified by the remainder of the statutory scheme
. . . because only one of the permissible meanings
produces a substantive effect that is compatible with the rest of
the law.” United Sav. Assn. of Tex. v. Timbers of Inwood
Forest Associates, Ltd., 484 U. S. 365, 371 (1988) . Thus, an
agency interpretation that is “inconsisten[t] with the design
and structure of the statute as a whole,” University of Tex.
Southwestern Medical Center v. Nassar, 570 U. S. ___, ___
(2013) (slip op., at 13), does not merit deference.

															     EPA itself has
repeatedly acknowledged that applying the PSD and Title V
permitting requirements to greenhouse gases would be inconsistent
with—in fact, would overthrow—the Act’s structure
and design. In the Tailoring Rule, EPA described the calamitous
consequences of interpreting the Act in that way. Under the PSD
program, annual permit applications would jump from about 800 to
nearly 82,000; annual administrative costs would swell from $12
million to over $1.5 billion; and decade-long delays in issuing
permits would become common, causing construction projects to grind
to a halt nationwide. Tailoring Rule 31557. The picture under Title
V was equally bleak: The number of sources required to have permits
would jump from fewer than 15,000 to about 6.1 million; annual
administrative costs would balloon from $62 million to $21 billion;
and collectively the newly covered sources would face permitting
costs of $147 billion. Id., at 31562–31563. Moreover,
“the great majority of additional sources brought into the
PSD and title V programs would be small sources that Congress did
not expect would need to undergo permitting.” Id., at 31533.
EPA stated that these results would be so “contrary to
congressional intent,” and would so “severely undermine
what Congress sought to accomplish,” that they necessitated
as much as a 1,000-fold increase in the permitting thresholds set
forth in the statute. Id., at 31554, 31562.

															     Like EPA, we think it
beyond reasonable debate that requiring permits for sources based
solely on their emission of greenhouse gases at the 100- and
250-tons-per-year levels set forth in the statute would be
“incompatible” with “the substance of
Congress’ regulatory scheme.” Brown & Williamson,
529 U. S., at 156. A brief review of the relevant statutory
provisions leaves no doubt that the PSD program and Title V are
designed to apply to, and cannot rationally be extended beyond, a
relative handful of large sources capable of shouldering heavy
substantive and procedural burdens.

															     Start with the PSD
program, which imposes numerous and costly requirements on those
sources that are required to apply for permits. Among other things,
the applicant must make available a detailed scientific analysis of
the source’s potential pollution-related impacts, demonstrate
that the source will not contribute to the violation of any
applicable pollution standard, and identify and use the “best
available control technology” for each regulated pollutant it
emits. §7475(a)(3), (4), (6), (e). The permitting authority
(the State, usually) also bears its share of the burden: It must
grant or deny a permit within a year, during which time it must
hold a public hearing on the application. §7475(a)(2), (c).
Not surprisingly, EPA acknowledges that PSD review is a
“complicated, resource-intensive, time-consuming, and
sometimes contentious process” suitable for “hundreds
of larger sources,” not “tens of thousands of smaller
sources.” 74 Fed. Reg. 55304, 55321–55322.

															     Title V contains no
comparable substantive requirements but imposes elaborate
procedural mandates. It requires the applicant to submit, within a
year of becoming subject to Title V, a permit application and a
“compliance plan” describing how it will comply with
“all applicable requirements” under the Act; to certify
its compliance annually; and to submit to “inspection, entry,
monitoring, . . . and reporting requirements.”
§§7661b(b)–(c), 7661c(a)–(c). The procedural
burdens on the permitting authority and EPA are also significant.
The permitting authority must hold a public hearing on the
application, §7661a(b)(6), and it must forward the application
and any proposed permit to EPA and neighboring States and respond
in writing to their comments, §7661d(a), (b)(1). If it fails
to issue or deny the permit within 18 months, any interested party
can sue to require a decision “without additional
delay.” §§7661a(b)(7), 7661b(c). An interested
party also can petition EPA to block issuance of the permit; EPA
must grant or deny the petition within 60 days, and its decision
may be challenged in federal court. §7661d(b)(2)–(3). As
EPA wrote, Title V is “finely crafted for thousands,”
not millions, of sources. Tailoring Rule 31563.

															     The fact that
EPA’s greenhouse-gas-inclusive interpretation of the PSD and
Title V triggers would place plainly excessive demands on limited
governmental resources is alone a good reason for rejecting it; but
that is not the only reason. EPA’s interpretation is also
unreasonable because it would bring about an enormous and
transformative expansion in EPA’s regulatory authority
without clear congressional authorization. When an agency claims to
discover in a long-extant statute an unheralded power to regulate
“a significant portion of the American economy,” Brown
& Williamson, 529 U. S., at 159, we typically greet its
announcement with a measure of skepticism. We expect Congress to
speak clearly if it wishes to assign to an agency decisions of vast
“economic and political significance.” Id., at 160; see
also MCI Telecommunications Corp. v. American Telephone &
Telegraph Co., 512 U. S. 218, 231 (1994) ; Industrial Union
Dept., AFL–CIO v. American Petroleum Institute, 448
U. S. 607 –646 (1980) (plurality opinion). The power to
require permits for the construction and modification of tens of
thousands, and the operation of millions, of small sources
nationwide falls comfortably within the class of authorizations
that we have been reluctant to read into ambiguous statutory text.
Moreover, in EPA’s assertion of that authority, we confront a
singular situation: an agency laying claim to extravagant statutory
power over the national economy while at the same time strenuously
asserting that the authority claimed would render the statute
“unrecognizable to the Congress that designed” it.
Tailoring Rule 31555. Since, as we hold above, the statute does not
compel EPA’s interpretation, it would be patently
unreason-able—not to say outrageous—for EPA to insist
on seizing expansive power that it admits the statute is not
designed to grant.[ 7 ]

															3

															     EPA thought that
despite the foregoing problems, it could make its interpretation
reasonable by adjusting the levels at which a source’s
greenhouse-gas emissions would oblige it to undergo PSD and Title V
permitting. Although the Act, in no uncertain terms, requires
permits for sources with the potential to emit more than 100 or 250
tons per year of a relevant pollutant, EPA in its Tailoring Rule
wrote a new threshold of 100,000 tons per year for greenhouse
gases. Since the Court of Appeals thought the statute unambiguously
made greenhouse gases capable of triggering PSD and Title V, it
held that petitioners lacked Article III standing to challenge the
Tailoring Rule because that rule did not injure petitioners but
merely relaxed the pre-existing statutory requirements. Because we,
however, hold that EPA’s greenhouse-gas-inclusive
interpretation of the triggers was not compelled, and because EPA
has essentially admitted that its interpretation would be
unreasonable without “tailoring,” we consider the
validity of the Tailoring Rule.

															     We conclude that
EPA’s rewriting of the statutory thresholds was impermissible
and therefore could not validate the Agency’s interpretation
of the triggering provisions. An agency has no power to
“tailor” legislation to bureaucratic policy goals by
rewriting unambiguous statutory terms. Agencies exercise discretion
only in the interstices created by statutory silence or ambiguity;
they must always “ ‘give effect to the
unambiguously expressed intent of Congress.’ ”
National Assn. of Home Builders v. Defenders of Wildlife, 551
U. S. 644, 665 (2007) (quoting Chevron, 467 U. S., at
843). It is hard to imagine a statutory term less ambiguous than
the precise numerical thresholds at which the Act requires PSD and
Title V permitting. When EPA replaced those numbers with others of
its own choosing, it went well beyond the “bounds of its
statutory authority.” Arlington, 569 U. S., at ___ (slip
op., at 5) (emphasis deleted).

															     The Solicitor General
does not, and cannot, defend the Tailoring Rule as an exercise of
EPA’s enforcement discretion. The Tailoring Rule is not just
an announcement of EPA’s refusal to enforce the statutory
permitting requirements; it purports to alter those requirements
and to establish with the force of law that otherwise-prohibited
conduct will not violate the Act. This alteration of the statutory
requirements was crucial to EPA’s “tailoring”
efforts. Without it, small entities with the potential to emit
greenhouse gases in amounts exceeding the statutory thresholds
would have remained subject to citizen suits—authorized by
the Act—to enjoin their construction, modification, or
operation and to impose civil penalties of up to $37,500 per day of
violation. §§7413(b), 7604(a), (f)(4); 40 CFR §19.4.
EPA itself has recently affirmed that the “independent
enforcement authority” furnished by the citizen-suit
provision cannot be displaced by a permitting authority’s
decision not to pursue enforcement. 78 Fed. Reg. 12477,
12486–12487 (2013). The Solicitor General is therefore quite
right to acknowledge that the availability of citizen suits made it
necessary for EPA, in seekingto mitigate the unreasonableness of
its greenhouse-gas-inclusive interpretation, to go beyond merely
exercising its enforcement discretion. See Tr. of Oral Arg.
87–88.

															     For similar reasons,
Morton v. Ruiz, 415 U. S. 199 (1974) —to which the
Solicitor General points as the best case supporting the Tailoring
Rule, see Tr. of Oral Arg. 71, 80–81—is irrelevant. In
Ruiz, Congress had appropriated funds for the Bureau of Indian
Affairs to spend on providing assistance to
“ ‘Indians throughout the United
States’ ” and had not “impose[d] any
geographical limitation on the availability of general assistance
benefits.” Id., at 206–207, and n. 7. Although we
held the Bureau could not deny benefits to off-reservation Indians
because it had not published its eligibility criteria, we stated in
dictum that the Bureau could, if it followed proper administrative
procedures, “create reasonable classifications and
eligibility requirements in order to allocate the limited funds
available.” Id., at 230–231. That dictum stands only
for the unremarkable proposition that an agency may adopt policies
to prioritize its expenditures within the bounds established by
Congress. See also Lincoln v. Vigil, 508 U. S. 182 –193
(1993). Nothing in Ruiz remotely authorizes an agency to modify
unambiguous requirements imposed by a federal statute. An agency
confronting resource constraints may change its own conduct, but it
cannot change the law.

															     Were we to recognize
the authority claimed by EPA in the Tailoring Rule, we would deal a
severe blow to the Constitution’s separation of powers. Under
our system of government, Congress makes laws and the President,
acting at times through agencies like EPA, “faithfully
execute[s]” them. U. S. Const., Art. II, §3;
see Medellín v. Texas, 552 U. S. 491 –527 (2008).
The power of executing the laws necessarily includes both authority
and responsibility to resolve some questions left open by Congress
that arise during the law’s administration. But it does not
include a power to revise clear statutory terms that turn out not
to work in practice. See, e.g., Barnhart v. Sigmon Coal Co., 534
U. S. 438, 462 (2002) (agency lacked authority “to
develop new guidelines or to assign liability in a manner
inconsistent with” an “unambiguous statute”).

															     In the Tailoring Rule,
EPA asserts newfound authority to regulate millions of small
sources—including retail stores, offices, apartment
buildings, shopping centers, schools, and churches—and to
decide, on an ongoing basis and without regard for the thresholds
prescribed by Congress, how many of those sources to regulate. We
are not willing to stand on the dock and wave goodbye as EPA
embarks on this multiyear voyage of discovery. We reaffirm the core
administrative-law principle that an agency may not rewrite clear
statutory terms to suit its own sense of how the statute should
operate. EPA therefore lacked authority to “tailor” the
Act’s unambiguous numerical thresholds to accommodate its
greenhouse-gas-inclusive interpretation of the permitting triggers.
Instead, the need to rewrite clear provisions of the statute should
have alerted EPA that it had taken a wrong interpretive turn.
Agencies are not free to “adopt . . . unreasonable
interpretations of statutory provisions and then edit other
statu-tory provisions to mitigate the unreasonableness.” App.
175, 2012 WL 6621785, *16 (Kavanaugh, J., dissenting from denial of
rehearing en banc). Because the Tailoring Rule cannot save
EPA’s interpretation of the triggers, that interpretation was
impermissible under Chevron.[ 8 ]

															B. BACT for “Anyway” Sources

															     For the reasons we
have given, EPA overstepped its statutory authority when it decided
that a source could become subject to PSD or Title V permitting by
reason of its greenhouse-gas emissions. But what about
“anyway” sources, those that would need permits based
on their emissions of more conventional pollutants (such as
particulate matter)? We now consider whether EPA reasonably
interpreted the Act to require those sources to comply with
“best available control technology” emission standards
for greenhouse gases.

															1

															     To obtain a PSD
permit, a source must be “subject to the best available
control technology” for “each pollutant subject to
regulation under [the Act]” that it emits. §7475(a)(4).
The Act defines BACT as “an emission limitation based on the
maximum degree of reduction of each pollutant subject to
regulation” that is “achievable . . . through
application of production processes and available methods, systems,
and techniques, including fuel cleaning, clean fuels, or treatment
or innovative fuel combustion techniques.” §7479(3).
BACT is determined “on a case-by-case basis, taking into
account energy, environmental, and economic impacts and other
costs.” Ibid.

															     Some petitioners urge
us to hold that EPA may never require BACT for greenhouse
gases—even when a source must undergo PSD review based on its
emissions of conventional pollutants—because BACT is
fundamentally unsuited to greenhouse-gas regulation. BACT, they
say, has traditionally been about end-of-stack controls “such
as catalytic converters or particle collectors”; but applying
it to greenhouse gases will make it more about regulating energy
use, which will enable regulators to control “every aspect of
a facility’s operation and design,” right down to the
“light bulbs in the factory cafeteria.” Brief for
Petitioner Energy-Intensive Manufacturers Working Group on
Greenhouse Gas Regulation et al. in No. 12–1254, p. 7;
see Joint Reply Brief for Petitioners in No. 12–1248 etc.,
pp. 14–15 (“BACT for [greenhouse gases] becomes an
unbounded exercise in command-and-control regulation” of
everything from “efficient light bulbs” to “basic
industrial processes”). But see Brief for Calpine Corp. as
Amicus Curiae 10 (“[I]n Calpine’s experience with
‘anyway’ sources, the [greenhouse-gas] analysis was
only a small part of the overall permitting process”).

															     EPA has published a
guidance document that lends some credence to petitioners’
fears. It states that at least initially, compulsory improvements
in energy efficiency will be the “foundation” of
greenhouse-gas BACT, with more traditional end-of-stack controls
either not used or “added as they become more
available.” PSD and Title V Permitting Guidance for
Greenhouse Gases 29 (Mar. 2011) (hereinafter Guidance); see Peloso
& Dobbins, Greenhouse Gas PSD Permitting: The Year in Review,
42 Tex. Env. L. J. 233, 247 (2012) (“Because [other
controls] tend to prove infeasible, energy efficiency measures
dominate the [greenhouse-gas] BACT controls approved by the states
and EPA”). But EPA’s guidance also states that BACT
analysis should consider options other than energy efficiency, such
as “carbon capture and storage.” Guidance 29, 32,
35–36, 42–43. EPA argues that carbon capture is
reasonably comparable to more traditional, end-of-stack BACT
technologies, id., at 32, n. 86, and petitioners do not dispute
that.

															     Moreover, assuming
without deciding that BACT may be used to force some improvements
in energy efficiency, there are important limitations on BACT that
may work to mitigate petitioners’ concerns about
“unbounded” regulatory authority. For one, BACT is
based on “control technology” for the applicant’s
“proposed facility,” §7475(a)(4); therefore, it
has long been held that BACT cannot be used to order a fundamental
redesign of the facility. See, e.g., Sierra Club v. EPA, 499
F. 3d 653, 654–655 (CA7 2007); In re Pennsauken
Cty., N. J., Resource Recovery Facility, 2 E. A. D.
667, 673 (EAB 1988). For another, EPA has long interpreted BACT as
required only for pollutants that the source itself emits, see 44
Fed. Reg. 51947 (1979); accordingly, EPA acknowledges that BACT may
not be used to require “reductions in a facility’s
demand for energy from the electric grid.” Guidance 24.
Finally, EPA’s guidance suggests that BACT should not require
every conceivable change that could result in minor improvements in
energy efficiency, such as the aforementioned light bulbs. Id., at
31. The guidance explains that permitting authorities should
instead consider whether a proposed regulatory burden outweighs any
reduction in emissions to be achieved, and should concentrate on
the facility’s equipment that uses the largest amounts of
energy. Ibid.

															2

															     The question before
us is whether EPA’s decision to require BACT for greenhouse
gases emitted by sources otherwise subject to PSD review is, as a
general matter, a permissible interpretation of the statute under
Chevron. We conclude that it is.

															     The text of the BACT
provision is far less open-ended than the text of the PSD and Title
V permitting triggers. It states that BACT is required “for
each pollutant subject to regulation under this chapter”
(i.e., the entire Act), §7475(a)(4), a phrase that—as
the D. C. Circuit wrote 35 years ago—“would not
seem readily susceptible [of] misinterpretation.” Alabama
Power Co. v. Costle, 636 F. 2d 323, 404 (1979). Whereas the
dubious breadth of “any air pollutant” in the
permitting triggers suggests a role for agency judgment in
identifying the subset of pollutants covered by the particular
regulatory program at issue, the more specific phrasing of the BACT
provision suggests that the necessary judgment has already been
made by Congress. The wider statutory context likewise does not
suggest that the BACT provision can bear a narrowing construction:
There is no indication that the Act elsewhere uses, or that EPA has
interpreted, “each pollutant subject to regulation under this
chapter” to mean anything other than what it says.

															     Even if the text were
not clear, applying BACT to greenhouse gases is not so disastrously
unworkable, and need not result in such a dramatic expansion of
agency authority, as to convince us that EPA’s interpretation
is unreasonable. We are not talking about extending EPA
jurisdiction over millions of previously unregulated entities, but
about moderately increasing the demands EPA (or a state permitting
authority) can make of entities already subject to its regulation.
And it is not yet clear that EPA’s demands will be of a
significantly different character from those traditionally
associated with PSD review. In short, the record before us does not
establish that the BACT provision as written is incapable of being
sensibly applied to greenhouse gases.

															     We acknowledge the
potential for greenhouse-gas BACT to lead to an unreasonable and
unanticipated degree of regulation, and our decision should not be
taken as an endorsement of all aspects of EPA’s current
approach, nor as a free rein for any future regulatory application
of BACT in this distinct context. Our narrow holding is that
nothing in the statute categorically prohibits EPA from
interpreting the BACT provision to apply to greenhouse gases
emitted by “anyway” sources.

															     However, EPA may
require an “anyway” source to comply with
greenhouse-gas BACT only if the source emits more than a de minimis
amount of greenhouse gases. As noted above, the Tailoring Rule
applies BACT only if a source emits greenhouse gases in excess of
75,000 tons per year CO2e, but the Rule makes clear that EPA did
not arrive at that number by identifying the de minimis level. See
nn. 1, 3, supra. EPA may establish an appropriate de minimis
threshold below which BACT is not required for a source’s
greenhouse-gas emissions. We do not hold that 75,000 tons per year
CO2e necessarily exceeds a true de minimis level, only that EPA
must justify its selection on proper grounds. Cf. Alabama Power,
supra, at 405.[ 9 ]

															*  *  *

															     To sum up: We hold
that EPA exceeded its statutory authority when it interpreted the
Clean Air Act to require PSD and Title V permitting for stationary
sources based on their greenhouse-gas emissions. Specifically, the
Agency may not treat greenhouse gases as a pollutant for pur-poses
of defining a “major emitting facility” (or a
“modification” thereof) in the PSD context or a
“major source” in the Title V context. To the extent
its regulations purport to do so, they are invalid. EPA may,
however, continue to treat greenhouse gases as a “pollutant
subject to regulation under this chapter” for purposes of
requiring BACT for “anyway” sources. The judgment of
the Court of Appeals is affirmed in part and reversed in part.

															It is so ordered. Notes 1 Although the statute sets
numerical thresholds (100 or 250 tons per year) for emissions that
will make a facility “major,” it does not specify by
how much a physical or operational change must increase emissions
to constitute a permit-requiring “modification.” Nor
does it say how much of a given regulated pollutant a “major
emitting facility” must emit before it is subject to BACT for
that pollutant. EPA, however, has established pollutant-specific
numerical thresholds below which a facility’s emissions of a
pollutant, and increases therein, are considered for those
purposes. See 40 CFR §§51.166(b)(2)(i), (23), (39),
(j)(2)–(3), 52.21(b)(2)(i), (23), (40), (j)(2)–(3); see
also v. , 636 F. 2d 323, 360–361, 400, 405 (CADC 1979)
(recognizing this authority in EPA); cf. v. , (“
. . . is part of the established background of legal
principles against which all enactments are
adopted”). 2 Comments from other
Executive Branch agencies reprinted in the notice echoed those
concerns. See, 73 Fed. Reg. 44360 (Departments of Agriculture,
Commerce, Transportation, and Energy noting EPA would
“exercis[e] de facto zoning authority through control
over thousands of what formerly were local or private decisions,
impacting the construction of schools, hospitals, and commercial
and residential development”); at 44383 (Council of Economic
Advisers and Office of Science and Technology Policy stating that
“[s]mall manufacturing facilities, schools, and shopping
centers” would be subject to “full major source
permitting”); at 44385 (Council on Environmental Quality
noting “the prospect of essentially automatic and immediate
regulation over a vast range of community and business
activity”); at 44391 (Small Business Administration finding
it “difficult to overemphasize how potentially disruptive and
burdensome such a new regulatory regime would be to small
entities” such as “office buildings, retail
establishments, hotels, . . . schools, prisons, and
private hospitals”). 3 EPA stated that its
adoption of a 75,000-tons-per-year threshold for emissions
requiring BACT and modifications requiring permits was not an
exercise of its authority to establish exceptions and that a truly
level might be “well below” 75,000 tons per year.
Tailoring Rule 31560; cf. n. 1, . 4 The Court of Appeals held
that petitioners’ arguments applied only to the PSD program
and that petitioners had therefore “forfeited any challenges
to EPA’s greenhouse gas-inclusive interpretation of Title
V.” 684 F. 3d, at 136. The Solicitor General does not
defend the Court of Appeals’ ruling on forfeiture, and he
concedes that some of the arguments petitioners have made before
this Court apply to Title V as well as the PSD program. See Brief
for Federal Respondents 56. We agree, and we are satisfied that
those arguments were also made below. See, Brief for State
Petitioners et al. in No. 10–1073 etc. (CADC), pp.
59–73; Brief for Non-State Petitioners et al. in No.
10–1073 etc. (CADC), pp. 46–47. 5 Our decision in v. , 564
U. S. ___ (2011), does not suggest otherwise. We there held
that the Act’s authorization for EPA to establish performance
standards for powerplant greenhouse-gas emissions displaced any
federal-common-law right that might otherwise have existed to seek
abatement of those emissions. at ___ (slip op., at 10). The
authorization to which we referred was that given in the NSPS
program of §7411, a part of the Act not at issue here and one
that no party in argued was ill suited to accommodating greenhouse
gases. 6 During the course of this
litigation, several possible limiting constructions for the PSD
trigger have been proposed. Judge Kavanaugh argued below that it
would be plausible for EPA to read “any air pollutant”
in the PSD context as limited to the six NAAQS pollutants. See v. ,
No. 09–1322 etc. (CADC, Dec. 20, 2012), App. 171–180,
2012 WL 6621785, *15–*18 (opinion dissenting from denial of
rehearing en banc). Some petitioners make a slightly different
argument: that because PSD permitting is required only for major
emitting facilities “in any area to which [the PSD program]
applies,” §7475(a), the relevant pollutants are only
those NAAQS pollutants for which the area in question is designated
attainment or unclassifiable. That approach would bring EPA’s
interpretation of the PSD trigger in line with its longstanding
interpretation of the permitting requirements for nonattainment
areas. Others maintain that “any air pollutant” in the
PSD provision should be limited to air pollutants with localized
effects on air quality. We do not foreclose EPA or the courts from
considering those constructions in the future, but we need not do
so today. 7 A few additional points
bear mentioning. The Solicitor General conjectures that EPA might
eventually alter its longstanding interpretation of
“potential to emit” in order to reduce the number of
sources required to have permits at the statutory thresholds. But
neither he nor the Agency has given us any reason to believe that
there exists a plausible reading of “potential to emit”
that EPA would willingly adopt and that would eliminate the
unreasonableness of EPA’s interpretation. Nor have we been
given any information about the ability of other possible
“streamlining” techniques alluded to by EPA—such
as “general” or “electronic”
permitting—to reduce the administrability problems identified
above; and in any event, none of those techniques would address the
more fundamental problem of EPA’s claiming regulatory
authority over millions of small entities that it acknowledges the
Act does not seek to regulate. Finally, the Solicitor General
suggests that the incompatibility of greenhouse gases with the PSD
program and Title V results chiefly from the inclusion of carbon
dioxide in the “aggregate pollutant” defined by EPA. We
decide these cases on the basis of the pollutant “greenhouse
gases” as EPA has defined and regulated it, and we express no
view on how our analysis might change were EPA to define it
differently. 8 argues, at 10 (opinion
concurring in part and dissenting in part), that when the statutory
permitting thresholds of 100 or 250 tons per year do not provide a
“sensible regulatory line,” EPA is entitled to
“read an unwritten exception” into “the
particular number used by the statute”—by which he
apparently means that the Agency is entitled to substitute a
dramatically higher number, such as 100,000. We are aware of no
principle of administrative law that would allow an agency to
rewrite such a clear statutory term, and we shudder to contemplate
the effect that such a principle would have on demo-cratic
governance. 9 argues that BACT is
“fundamentally incompatible” with greenhouse gases for
two reasons. at 4 (opinion concurring in part and dissenting in
part). First, BACT requires consideration of “ambient air
quality at the proposed site and in areas which may be affected by
emissions from [the proposed] facility for each pollutant subject
to regulation under this chapter,” §7475(e)(1); see also
§7475(e)(3)(B); and it is not obvious how that requirement
should apply, or even whether it can apply, to greenhouse gases. ,
at 4–5. But the possibility that that requirement may be
inoperative as to greenhouse gases does not convince us that they
must be categorically excluded from BACT even though they are
indisputably a “pollutant subject to regulation.”
Second, argues that EPA’s guidance on how to implement
greenhouse-gas BACT is a recipe for “arbitrary and
inconsistent decisionmaking.” at 8. But we are not reviewing
EPA’s guidance in these cases, and we cannot say that it is
impossible for EPA and state permitting authorities to devise
rational ways of complying with the statute’s directive to
determine BACT for greenhouse gases “on a case-by-case basis,
taking into account energy, environmental, and economic impacts and
other costs.” §7479(3). SUPREME COURT OF THE UNITED STATES

															_________________

															Nos. 12–1146, 12–1248,
12–1254, 12–1268, 12–1269, and 12–1272

															_________________

															UTILITY AIR REGULATORY
GROUP,PETITIONER

															12–1146      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															AMERICAN CHEMISTRY COUNCIL,
et al.,PETITIONERS

															12–1248      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															ENERGY-INTENSIVE MANUFACTURERS
WORKINGGROUP ON GREENHOUSE GAS REGULATION,et al.,
PETITIONERS

															12–1254      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															SOUTHEASTERN LEGAL FOUNDATION,
INC.,et al., PETITIONERS

															12–1268      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															TEXAS, et al., PETITIONERS

															12–1269      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.; and

															CHAMBER OF COMMERCE OF THE UNITEDSTATES,
et al., PETITIONERS

															12–1272      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															on writs of certiorari to the united states
court ofappeals for the district of columbia circuit

															[June 23, 2014]

															     Justice Alito, with
whom Justice Thomas joins, concurring in part and dissenting in
part.

															     In Massachusetts v.
EPA, 549 U. S. 497 (2007) , this Court considered whether
greenhouse gases fall within the Clean Air Act’s general
definition of an air “pollutant.” Id., at
528–529. The Environmental Protection Agency cautioned us
that “key provisions of the [Act] cannot cogently be applied
to [greenhouse gas] emissions,” Brief for Federal Respondent
in Massachusetts v. EPA, O. T. 2006, No. 05–1120, p. 22, but
the Court brushed the warning aside and had “little
trouble” concluding that the Act’s “sweeping
definition” of a pollutant encompasses greenhouse gases. 549
U. S., at 528–529. I believed Massachusetts v. EPA was
wrongly decided at the time, and these cases further expose the
flaws with that decision.

															I

															     As the present cases
now show, trying to fit greenhouse gases into “key
provisions” of the Clean Air Act involves more than a
“little trouble.” These cases concern the provisions of
the Act relating to the “Prevention of Significant
Deterioration” (PSD), 42 U. S. C.
§§7470–7492, as well as Title V of the Act,
§7661. And in order to make those provisions apply to
greenhouse gases in a way that does not produce absurd results, the
EPA effectively amended the Act. The Act contains specific
emissions thresholds that trigger PSD and Title V coverage, but the
EPA crossed out the figures enacted by Congress and substituted
figures of its own.

															     I agree with the Court
that the EPA is neither required nor permitted to take this
extraordinary step, and I therefore join Parts I and II–A of
the Court’s opinion.

															II

															     I do not agree,
however, with the Court’s conclusion that what it terms
“anyway sources,” i.e., sources that are subject to PSD
and Title V permitting as the result of the emission of
conventional pollutants, must install “best available control
technology” (BACT) for greenhouse gases. As is the case with
the PSD and Title V thresholds,trying to fit greenhouse gases into
the BACT analysis badly distorts the scheme that Congress
adopted.

															     The Court gives two
main reasons for concluding that BACT applies to
“anyway” sources, one based on textand one based on
practical considerations. Neither isconvincing.

															A

															     With respect to the
text, it is curious that the Court, having departed from a literal
interpretation of the term “pollutant” in Part
II–A, turns on its heels and adopts a literal interpretation
in Part II–B. The coverage thresholds at issue in Part
II–A apply to any “pollutant.” The Act’s
general definition of this term is broad, and in Massachusetts v.
EPA, supra, the Court held that this definition covers greenhouse
gases. The Court does not disturb that holding, but it nevertheless
concludes that, as used in the provision triggering PSD coverage,
the term “pollutant” actually means “pollutant,
other than a greenhouse gas.”

															     In Part II–B, the
relevant statutory provision saysthat BACT must be installed for
any “pollutant subjectto regulation under [the Act].”
§7475(a)(4). If the term “pollutant” means
“pollutant, other than a greenhouse gas,” as the Court
effectively concludes in Part II–A, the term “pollutant
subject to regulation under [the Act]” in §7475(a)(4)
should mean “pollutant, other than a greenhouse gas, subject
to regulation under [the Act], and that is subject to regulation
under [the Act].” The Court’s literalism is selective,
and it results in a strange and disjointed regulatory scheme.

															     Under the Court’s
interpretation, a source can emit an unlimited quantity of
greenhouse gases without triggering the need for a PSD permit. Why
might Congress have wanted to allow this? The most likely
explanation is that the PSD permitting process is simply not suited
for use in regulating this particular pollutant. And if that is so,
it makes little sense to require the installation of BACT for
greenhouse gases in those instances in which a source happens to be
required to obtain a permit due to the emission of a qualifying
quantity of some other pollutant that is regulated under the
Act.

															B

															     The Court’s
second reason for holding that BACT applies to “anyway”
sources is its belief that this can be done without disastrous
consequences. Only time will tell whether this hope is well
founded, but it seems clear that BACT analysis is fundamentally
incompatible with the regulation of greenhouse-gas emissions for at
least two important reasons.

															1

															     First, BACT looks to
the effects of covered pollutants in the area in which a source is
located. The PSD program is implemented through “emission
limitations and such other measures” as are “necessary
. . . to prevent significant deterioration of air quality
in each region.” §7471 (emphasis added). The Clean Air
Act provides that BACT must be identified “on a case-by-case
basis,” §7479(3), and this necessarily means that local
conditions must be taken into account. For this reason, the Act
instructs the EPA to issue regulations requiring an analysis of
“the ambient air quality . . . at the site of the
proposed major emitting facil-ity and in the area potentially
affected by the emissions from such facility for each pollutant
regulated under [the Act].” §7475(e)(3)(B) (emphasis
added). The Act also requires a public hearing on “the air
quality at the proposed site and in areas which may be affected by
emissions from such facility for each pollutant subject to
regulation under [the Act] which will be emitted from such
facility.” §§7475(a)(2), (e)(1) (emphasis added).
Accordingly, if BACT is required for greenhouse gases, the Act
demands that the impact of these gases in the area surrounding a
site must be monitored, explored at a public hearing, and
considered as part of the permitting process. The effects of
greenhouse gases, however, are global, not local. See PSD and Title
V Permitting Guidance for Greenhouse Gases 41–42 (Mar. 2011)
(hereinafter Guidance). As a result, the EPA has declared that PSD
permit applicants and permitting officials may disregard these
provisions of the Act. 75 Fed. Reg. 31520 (2010).

															2

															     Second, as part of
the case-by-case analysis required by BACT, a permitting authority
must balance the environmental benefit expected to result from the
installation of an available control measure against adverse
consequences that may result, including any negative impact on the
environment, energy conservation, and the economy. And the EPA
itself has admitted that this cannot be done on a case-by-case
basis with respect to greenhouse gases.

															     The Clean Air Act makes
it clear that BACT must be determined on a “case-by-case
basis, taking into account energy, environmental, and economic
impacts and other costs.” §7479(3). To implement this
directive, the EPA adopted a five-step framework for making a BACT
determination. See New Source Review Workshop Manual: Prevention of
Significant Deterioration and Nonattainment Area Permitting (Oct.
1990).[ 1 ] Under the fourth step
of this analysis, potentially applicable and feasible control
technologies that are candidates for selection as BACT for a
particular source are eliminated from consideration based on their
“collateral impacts,” such as any adverse environmental
effects or adverse effects on energy consumption or the
economy.

															     More recently, the EPA
provided guidance to permitting authorities regarding the treatment
of greenhouse-gas emissions under this framework, and the
EPA’s guidance demonstrates the insuperable problem that
results when an attempt is made to apply this framework to
greenhouse gas emissions. As noted above, at step 4 of the
framework, a permitting authority must balance the positive effect
likely to result from requiring a particular source to install a
particular technology against a variety of negative effects that
are likely to occur if that step is taken. Butin the case of
greenhouse gases, how can a permit-ting authority make this
individualized, source-specific determination?

															     The EPA instructs
permitting authorities to take into consideration all the adverse
effects that the EPA has found to result from the overall increase
in greenhouse gases in the atmosphere. These include an increased
risk of dangerous heat waves, hurricanes, floods, wildfires, and
drought, as well as risks to agriculture, forestry, and water
resources. Guidance 40–41. But the EPA admits that it is
simply not possible for a permitting authority to calculate in any
meaningful way the degree to which any potential reduction in
greenhouse gas emissions from any individual source might reduce
these risks. And without making such a calculation in even a very
rough way, a permitting authority cannot do what the Clean Air Act
and the EPA’s framework demand—compare the benefits of
some specified reduction in the emission of greenhouse gases from a
particular source with any adverse environmental or economic
effects that might result from mandating such a reduction.

															     Suppose, for example,
that a permitting authority must decide whether to mandate a change
that both decreases a source’s emission of greenhouse gases
and increases its emission of a conventional pollutant that has a
negative effect on public health. How should a permitting authority
decide whether to require this change? Here is the EPA’s
advice:

															“[W]hen considering the trade-offs
between the environmental impacts of a particular level of GHG
[greenhouse gas] reduction and a collateral increase in another
regulated NSR pollutant,[[ 2 ]]
rather than attempting to determine or characterize specific
environmental impacts from GHGs emitted at particular locations,
EPA recommends that permitting authorities focus on the amount of
GHG emission reductions that may be gained or lost by employing a
particular control strategy and how that compares to the
environmental or other impacts resulting from the collateral
emissions increase of other regulated NSR pollutants.”
Guidance 42.

															     As best I can make out,
what this means is that permitting authorities should not even try
to assess the net impact on public health. Instead of comparing the
positive and negative public health effects of a particular option,
permitting authorities are instructed to compare the adverse public
health effects of increasing the emissions of the conventional
pollutants with the amount of the reduction of the source’s
emissions of greenhouse gases. But without knowing the positive
effects of the latter, this is a meaningless comparison.

															     The EPA tries to
ameliorate this problem by noting that permitting authorities are
entitled to “a great deal of discretion,” Guidance 41,
but without a comprehensible standard, what this will mean is
arbitrary and inconsistent decisionmaking. That is not what the
Clean Air Act contemplates.[ 3 ]

															*  *  *

															     BACT analysis, like
the rest of the Clean Air Act, was developed for use in regulating
the emission of conventional pollutants and is simply not suited
for use with respect to greenhouse gases. I therefore respectfully
dissent from Part II–B–2 of the opinion of the
Court. Notes 1 The EPA describes these
steps as follows: 2 “New source review
pollutants” are those pollutants for which a National Ambient
Air Quality standard has been set and a few others, such as sulphur
dioxide. See 40 CFR 51.165(a)(1)(xxxvii) (2013). 3 While I do not think that
BACT applies at all to “anyway sources,” if it is to
apply, the limitations suggested in Part II–B–1 might
lessen the inconsistencies highlighted in Part II of this opinion,
and on that understanding I join Part
II–B–1. SUPREME COURT OF THE UNITED STATES

															_________________

															Nos. 12–1146, 12–1248,
12–1254, 12–1268, 12–1269, and 12–1272

															_________________

															UTILITY AIR REGULATORY
GROUP,PETITIONER

															12–1146      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															AMERICAN CHEMISTRY COUNCIL,
et al.,PETITIONERS

															12–1248      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															ENERGY-INTENSIVE MANUFACTURERS
WORKINGGROUP ON GREENHOUSE GAS REGULATION,et al.,
PETITIONERS

															12–1254      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															SOUTHEASTERN LEGAL FOUNDATION,
INC.,et al., PETITIONERS

															12–1268      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															TEXAS, et al., PETITIONERS

															12–1269      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.; and

															CHAMBER OF COMMERCE OF THE UNITEDSTATES,
et al., PETITIONERS

															12–1272      v.

															ENVIRONMENTAL PROTECTION AGENCY,
et al.;

															on writs of certiorari to the united states
court ofappeals for the district of columbia circuit

															[June 23, 2014]

															     Justice Breyer, with
whom Justice Ginsburg, Justice Sotomayor, and Justice Kagan join,
concurring in part and dissenting in part.

															     In Massachusetts v.
EPA, 549 U. S. 497 (2007) , we held that greenhouse gases fall
within the Clean Air Act’s general definition of the term
“air pollutant,” 42 U. S. C. §7602(g).
549 U. S., at 528–529. We also held, consequently, that
the Environmental Protection Agency is empowered and required by
Title II of the Act to regulate greenhouse gas emissions from
mobile sources (such as cars and trucks) if it decides that
greenhouse gases “contribute to . . . air pollution
which may reasonably be anticipated to endanger public health or
welfare,” §7521(a)(1). 549 U. S., at 532–533.
The EPA determined that greenhouse gases endanger human health and
welfare, 74 Fed. Reg. 66496 (2009) (Endangerment Finding), and so
it issued regulations for mobile emissions, 75 Fed. Reg. 25324
(2010) (Tailpipe Rule).

															     These cases take as a
given our decision in Massachusetts that the Act’s general
definition of “air pollutant” includes greenhouse
gases. One of the questions posed by these cases is whether those
gases fall within the scope of the phrase “any air
pollutant” as that phrase is used in the more specific
provisions of the Act here at issue. The Court’s answer is
“no.” Ante, at 10–24. I disagree.

															     The Clean Air Act
provisions at issue here are Title I’s Prevention of
Significant Deterioration (PSD) program, §7470 et seq., and
Title V’s permitting regime, §7661 et seq. By contrast
to Title II, Titles I and V apply to stationary sources, such as
power plants and factories. Under the PSD program, “major
emitting facilities” constructed in the United States must
meet certain requirements, including obtaining a permit that
imposes emissions limitations, §7475(a)(1), and using
“the best available control technology for each pollutant
subject to regulation under [the Act] emitted from” the
facility, §7475(a)(4). Title V requires each “major
source” to obtain an operating permit. §7661a(a).

															     These cases concern the
definitions of “major emitting facility” and
“major source,” each of which is defined to mean any
stationary source that emits more than a threshold quantity of
“any air pollutant.” See §7479(1) (“major
emitting facility”); §§7602(j), 7661(2)(B)
(“major source”). To simplify the exposition, I will
refer only to the PSD program and its definition of “major
emitting facility”; a parallel analysis applies to Title
V.

															     As it is used in the
PSD provisions,

															“[t]he term ‘major emitting
facility’ means any of [a list of specific categories of]
stationary sources of air pollutants which emit, or have the
potential to emit, one hundred tons per year or more of any air
pollutant . . . . Such term also includes any other
source with the potential to emit two hundred and fifty tons per
year or more of any air pollutant.” §7479(1).

															To simplify further, I will ignore the reference
to specific types of source that emit at least 100 tons per year
(tpy) of any air pollutant. In effect, we are dealing with a
statute that says that the PSD program’s regulatory
requirements must be applied to

															“any stationary source that has the
potential to emit two hundred fifty tons per year or more of any
airpollutant.”

															     The interpretive
difficulty in these cases arises out of the definition’s use
of the phrase “two hundred fifty tons per year or
more,” which I will call the “250 tpy threshold.”
When applied to greenhouse gases, 250 tpy is far too low a
threshold. As the Court explains, tens of thousands of stationary
sources emit large quantities of one greenhouse gas, carbon
dioxide. See ante, at 17–20, and n. 7. To apply the
programs at issue here to all those sources would be extremely
expensive and burdensome, counterproductive, and perhaps
impossible; it would also contravene Congress’s intent that
the programs’ coverage be limited to those large sources
whose emissions are substantial enough to justify the regulatory
burdens. Ibid. The EPA recognized as much, and it addressed the
problem by issuing a regulation—the Tailoring Rule—that
purports to raise the coverage threshold for greenhouse gases from
the statutory figure of 250 tpy to 100,000 tpyin order to keep the
programs’ coverage limited to “a rela-tively small
number of large industrial sources.” 75 Fed. Reg. 31514,
31555 (2010); see id., at 31523–31524.

															     The Tailoring Rule
solves the practical problems that would have been caused by the
250 tpy threshold. But what are we to do about the statute’s
language? The statute specifies a definite number—250, not
100,000—and it says that facilities that are covered by that
number must meet the program’s requirements. The statute says
nothing about agency discretion to change that number. What is to
be done? How, given the statute’s language, can the EPA
exempt from regulation sources that emit more than 250 but less
than 100,000 tpy of greenhouse gases (and that also do not emit
other regulated pollutants at threshold levels)?

															     The Court answers by
(1) pointing out that regulation at the 250 tpy threshold would
produce absurd results, (2) refusing to read the statute as
compelling such results, and (3) consequently interpreting the
phrase “any air pollutant” as containing an implicit
exception for greenhouse gases. (Emphasis added.) Put differently,
the Court reads the statute as defining “major emitting
facility”to mean “stationary sources that have the
potential to emit two hundred fifty tons per year or more of any
air pollutant except for those air pollutants, such as carbon
dioxide, with respect to which regulation at that threshold would
be impractical or absurd or would sweep in smaller sources that
Congress did not mean to cover.” See ante, at 15–16
(“[T]here is no insuperable textual barrier to EPA’s
interpreting ‘any air pollutant’ in the permitting
triggers of PSD and Title V to encompass only pollutants emitted in
quantities that enable them to be sensibly regulated at the
statutory thresholds, and to exclude those atypical pollutants
that, like greenhouse gases, are emitted in such vast quantities
that their inclusion would radically transform those programs and
render them unworkable as written”).

															     I agree with the Court
that the word “any,” when used in a statute, does not
normally mean “any in the universe.” Cf. FCC v.
NextWave Personal Communications Inc., 537 U. S. 293, 311
(2003) (Breyer, J., dissenting) (“ ‘Tell all
customers that . . .’ does not refer to every
customer of every business in the world”). Rather,
“[g]eneral terms as used on particular occasions often carry
with them implied restrictions as to scope,” ibid., and so
courts must interpret the word “any,” like all other
words, in context. As Judge Learned Hand pointed out when
interpreting another statute many years ago, “[w]e can best
reach the meaning here, as always, by recourse to the underlying
purpose, and, with that as a guide, by trying to project upon the
specific occasion how we think persons, actuated by such a purpose,
would have dealt with it, if it had been presented to them at the
time.” Borella v. Borden Co., 145 F. 2d 63, 64 (CA2
1944). The pursuit of that underlying purpose may sometimes require
us to “abandon” a “literal interpretation”
of a word like “any.” Id., at 64–65.

															     The law has long
recognized that terms such as “any” admit of unwritten
limitations and exceptions. Legal philosophers like to point out
that a statute providing that “ ‘[w]hoever shall
willfully take the life of another shall be punished by
death’ ” need not encompass a man who kills in
self-defense; nor must an ordinance imposing fines upon those who
occupy a public parking spot for more than two hours penalize a
driver who is unable to move because of a parade. See Fuller, The
Case of the Speluncean Explorers, 62 Harv. L. Rev. 616, 619,
624 (1949); see also United States v. Kirby, 7 Wall. 482,
485–487 (1869) (holding that a statute forbidding knowing and
willful obstruction of the mail contains an implicit exception
permitting a local sheriff to arrest a mail carrier). The maxim
cessante ratione legis cessat ipse lex—where a law’s
rationale ceases to apply, so does the law itself—is not of
recent origin. See, e.g., Zadvydas v. Davis, 533 U. S. 678,
699 (2001) (citing 1 E. Coke, Institutes *70b); Green v. Liter, 8
Cranch 229, 249 (1814) (Story, J.) (“cessante ratione, cessat
ipsa lex”).

															     I also agree with the
Court’s point that “a generic reference to air
pollutants” in the Clean Air Act need not “encompass
every substance falling within the Act-wide definition” that
we construed in Massachusetts, §7602(g). See ante, at
12–13. As the Court notes, the EPA has interpreted the phrase
“any air pollutant,” which is used several times in the
Act, as limited to “air pollutants for which EPA has
promulgated [new source performance standards]” in the
portion of the Act dealing with those standards, as limited to
“visibility-impairing air pollutants” in the part of
the Act concerned with deleterious effects on visibility, and as
limited to “pollutants for which the area is designated
nonattainment” in the part of the Act aimed at regions that
fail to attain air quality standards. Ibid.

															     But I do not agree with
the Court that the only way to avoid an absurd or otherwise
impermissible result in these cases is to create an atextual
greenhouse gas exception to the phrase “any air
pollutant.” After all, the word “any” makes an
earlier appearance in the definitional provision, which defines
“major emitting facility” to mean “any
. . . source with the potential to emit two hundred and
fifty tons per year or more of any air pollutant.”
§7479(1) (emphasis added). As a linguistic matter, one can
just as easily read an implicit exception for small-scale
greenhouse gas emissions into the phrase “any source”
as into the phrase “any air pollutant.” And given the
purposes of the PSD program and the Act as a whole, as well as the
specific roles of the different parts of the statutory definition,
finding flexibility in “any source” is far more
sensible than the Court’s route of finding it in “any
air pollutant.”

															     The implicit exception
I propose reads almost word for word the same as the Court’s,
except that the location of the exception has shifted. To repeat,
the Court reads the definition of “major emitting
facility” as if it referred to “any source with the
potential to emit two hundred fifty tons per year or more of any
air pollutant except for those air pollutants, such as carbon
dioxide, with respect to which regulation at that threshold would
be impractical or absurd or would sweep in smaller sources that
Congress did not mean to cover.” I would simply move the
implicit exception, which I’ve italicized, so that it applies
to “source” rather than “air pollutant”:
“any source with the potential to emit two hundred fifty tons
per year or more of any air pollutant except for those sources,
such as those emitting unmanageably small amounts of greenhouse
gases, with respect to which regulation at that threshold would be
impractical or absurd or would sweep in smaller sources that
Congress did not mean to cover.”

															     From a legal,
administrative, and functional perspective—that is, from a
perspective that assumes that Congress was not merely trying to
arrange words on paper but was seeking to achieve a real-world
purpose—my way of reading the statute is the more sensible
one. For one thing, my reading is consistent with the specific
purpose underlying the 250 tpy threshold specified by the statute.
The purpose of that number was not to prevent the regulation of
dangerous air pollutants that cannot be sensibly regulated at that
particular threshold, though that is the effect that the
Court’s reading gives the threshold. Rather, the purpose was
to limit the PSD program’s obligations to larger sources
while exempting the many small sources whose emissions are low
enough that imposing burdensome regulatory requirements on them
would be senseless.

															     Thus, the accompanying
Senate Report explains that the PSD program “is reasonable
and necessary for very large sources, such as new electrical
generating plants or new steel mills. But the procedure would prove
costly and potentially unreasonable if imposed on construction of
storage facilities for a small gasoline jobber or on the
construction of a new heating plant at a junior college.”
S. Rep. No. 95–127, p. 96 (1977). And the principal
sponsor of the Clean Air Act amendments at issue here, Senator
Edmund Muskie, told the Senate that the program would not cover
“houses, dairies, farms, highways, hospitals, schools,
grocery stores, and other such sources.” 123 Cong. Rec.
18013, 18021 (1977).

															     The EPA, exercising the
legal authority to which it is entitled under Chevron
U. S. A. Inc. v. Natural Resources Defense Council, Inc.,
467 U. S. 837 (1984) , understood the threshold’s
purpose in the same light. It explained that Congress’s
objective was

															“to limit the PSD program to large
industrial sources because it was those sources that were the
primary cause of the pollution problems in question and because
those sources would have the resources to comply with the PSD
requirements. Congress’s mechanism for limiting PSD was the
100/250 tpy threshold limitations. Focused as it was primarily on
NAAQS pollutants [that is, those air pollutants for which the EPA
has issued a national ambient air quality standard under Title I of
the Act, see EPA v. EME Homer City Generation, L. P., 572
U. S. ___, ___ (2014) (slip op., at 4)], Congress considered
sources that emit NAAQS pollutants in those quantities generally to
be the large industrial sources to which it intended PSD to be
limited.” Tailoring Rule, 75 Fed. Reg. 31555.

															     The Court similarly
acknowledges that “the PSD program and Title V are designed
to apply to, and cannot rationally be extended beyond, a relative
handful of large sources capable of shouldering heavy substantive
and procedural burdens.” Ante, at 18; see also Alabama Power
Co. v. Costle, 636 F. 2d 323, 353 (CADC 1979)
(“Congress’s intention was to identify facilities
which, due to their size, are financially able to bear the
substantial regulatory costs imposed by the PSD provisions and
which, as a group, are primarily responsible for emission of the
deleterious pollutants that befoul our nation’s
air”).

															     An implicit
source-related exception would serve this statutory purpose while
going no further. The implicit exception that the Court reads into
the phrase “any air pollutant,” by contrast, goes well
beyond the limited congressional objective. Nothing in the
statutory text, the legislative history, or common sense suggests
that Congress, when it imposed the 250 tpy threshold, was trying to
undermine its own deliberate decision to use the broad language
“any air pollutant” by removing some substances (rather
than some facilities) from the PSD program’s coverage.

															     For another thing, a
source-related exception serves the flexible nature of the Clean
Air Act. We observed in Massachusetts that “[w]hile the
Congresses that drafted” the Act “might not have
appreciated the possibility that burning fossil fuels could lead to
global warming, they did understand that without regulatory
flexibility, changing circumstances and scientific developments
would soon render the Clean Air Act obsolete.” 549
U. S., at 532. We recognized that “[t]he broad language
of” the Act-wide definition of “air pollutant”
“reflects an intentional effort to confer the flexibility
necessary to forestall such obsolescence.” Ibid.

															     The Court’s
decision to read greenhouse gases out of the PSD program drains the
Act of its flexibility and chips away at our decision in
Massachusetts. What sense does it make to read the Act as generally
granting the EPA the authority to regulate greenhouse gas emissions
and then to read it as denying that power with respect to the
programs for large stationary sources at issue here? It is
anomalous to read the Act to require the EPA to regulate air
pollutants that pose previously unforeseen threats to human health
and welfare where “250 tons per year” is a sensible
regulatory line but not where, by chemical or regulatory
happenstance, a higher line must be drawn. And it is anomalous to
read an unwritten exception into the more important phrase of the
statutory definition (“any air pollutant”) when a
similar unwritten exception to less important language (the
particular number used by the statute) will do just as well. The
implicit exception preferred by the Court produces all of these
anomalies, while the source-related exception I propose creates
none of them.

															     In addition, the
interpretation I propose leaves the EPA with the sort of discretion
as to interstitial matters that Congress likely intended it to
retain. My interpretation gives the EPA nothing more than the
authority to exempt sources from regulation insofar as the Agency
reasonably determines that applying the PSD program to them would
expand the program so much as to contravene Congress’s
intent. That sort of decision, which involves the Agency’s
technical expertise and administrative experience, is the kind of
decision that Congress typically leaves to the agencies to make.
Cf. Barnhart v. Walton, 535 U. S. 212, 222 (2002) (enumerating
factors that we take to indicate that Congress intends the agency
to exercise the discre-tion provided by Chevron). To read the Act
to grant that discretion here is to read it as furthering
Congress’s (and the public’s) interest in more
effective, less wastefulregulation.

															     Last, but by no means
least, a source-related exception advances the Act’s overall
purpose. That broad purpose, as set forth at the beginning of the
statute, is “to protect and enhance the quality of the
Nation’s air resources so as to promote the public health and
welfare and the productive capacity of its population.”
§7401(b)(1); see also §7470(1) (A purpose of the PSD
program in particularis “to protect public health and welfare
from any actualor potential adverse effect which in the
Administra-tor’s judgment may reasonably be anticipate[d] to
occur from air pollution”); §7602(h) (“All
language [in the Act] referring to effects on welfare includes
. . . effects on . . . weather . . .
and climate”). The expert agency charged with administering
the Act has determined in its En-dangerment Finding that greenhouse
gases endanger human health and welfare, and so sensible regulation
of industrial emissions of those pollutants is at the core of the
purpose behind the Act. The broad “no greenhouse gases”
exception that the Court reads into the statute unnecessarily
undercuts that purpose, while my narrow source-related exception
would leave the Agency with the tools it needs to further it.

															*  *  *

															     I agree with the
Court’s holding that stationary sources that are subject to
the PSD program because they emit other (non-greenhouse-gas)
pollutants in quantities above the statutory threshold—those
facilities that the Court refers to as “anyway”
sources—must meet the “best available control
technology” requirement of §7475(a)(4) with respect to
greenhouse gas emissions. I therefore join Part II–B–2
of the Court’s opinion. But as for the Court’s holding
that the EPA cannot interpret the language at issue here to cover
facilities that emit more than 100,000 tpy of greenhouse gases by
virtue of those emissions, I respectfully dissent.

Summary: The Supreme Court ruled that the Environmental Protection Agency (EPA) overstepped its authority in regulating greenhouse gas emissions from stationary sources, such as factories and power plants, based solely on the EPA's previous regulation of greenhouse gas emissions from motor vehicles. The Court found that the EPA's interpretation of the Clean Air Act was impermissible and that the EPA has the authority to exempt sources from regulation if applying the regulation would significantly expand the program contrary to Congress's intent. The Court's decision considered the Act's overall purpose of protecting public health and welfare from adverse effects of air pollution, including climate change, while also ensuring effective and less wasteful regulation.