U.S. Supreme Court Dow Chemical Co. v. United States, 476
U.S. 227 (1986) Dow Chemical Co. v. United
States No. 84-1259 Argued December 10,
1985 Decided May 19, 1986 476
U.S. 227 CERTIORARI TO THE UNITED STATES
COURT OF APPEALS FOR THE SIXTH CIRCUIT Syllabus Petitioner operates a 2,000-acre chemical plant consisting of
numerous covered buildings, with outdoor manufacturing equipment
and piping conduits located between the various buildings exposed
to visual observation from the air. Petitioner maintains elaborate
security around the perimeter of the complex, barring ground-level
public views of the area. When petitioner denied a request by the
Environmental Protection Agency (EPA) for an on-site inspection of
the plant, EPA did not seek an administrative search warrant, but
instead employed a commercial aerial photographer, using a standard
precision aerial mapping camera, to take photographs of the
facility from various altitudes, all of which were within lawful
navigable airspace. Upon becoming aware of the aerial photography,
petitioner brought suit in Federal District Court, alleging that
EPA's action violated the Fourth Amendment and was beyond its
statutory investigative authority. The District Court granted
summary judgment for petitioner, but the Court of Appeals reversed,
holding that EPA's aerial observation did not exceed its
investigatory authority and that the aerial photography of
petitioner's plant complex without a warrant was not a search
prohibited by the Fourth Amendment. Held: 1. The fact that aerial photography by petitioner's competitors
might be barred by state trade secrets law is irrelevant to the
questions presented in this case. Governments do not generally seek
to appropriate trade secrets of the private sector, and the right
to be free of appropriation of trade secrets is protected by law.
Moreover, state tort law governing unfair competition does not
define the limits of the Fourth Amendment. Pp. 476 U. S.
231 -233.

															2. The use of aerial observation and photography is within EPA's
statutory authority. When Congress invests an agency such as EPA
with enforcement and investigatory authority, it is not necessary
to identify explicitly every technique that may be used in the
course of executing the statutory mission. Although § 114(a) of the
Clean Air Act, which provides for EPA's right of entry to premises
for inspection purposes, Page 476 U. S. 228 does not authorize aerial observation, that section appears to
expand, not restrict, EPA's general investigatory powers, and there
is no suggestion in the statute that the powers conferred by §
114(a) are intended to be exclusive. EPA needs no explicit
statutory provision to employ methods of observation commonly
available to the public at large. Pp. 476 U. S.
233 -234.

															3. EPA's taking, without a warrant, of aerial photographs of
petitioner's plant complex from an aircraft lawfully in public
navigable airspace was not a search prohibited by the Fourth
Amendment. The open areas of an industrial plant complex such as
petitioner's are not analogous to the "curtilage" of a dwelling,
which is entitled to protection as a place where the occupants have
a reasonable and legitimate expectation of privacy that society is
prepared to accept. See California v. Ciraolo, ante, p. 476 U. S. 207 . The
intimate activities associated with family privacy and the home and
its curtilage simply do not reach the outdoor areas or spaces
between structures and buildings of a manufacturing plant. For
purposes of aerial surveillance, the open areas of an industrial
complex are more comparable to an "open field" in which an
individual may not legitimately demand privacy. Oliver v.
United States, 466 U. S. 170 .
Here, EPA was not employing some unique sensory device not
available to the public, but rather was employing a conventional,
albeit precise, commercial camera commonly used in mapmaking. The
photographs were not so revealing of intimate details as to raise
constitutional concerns. The mere fact that human vision is
enhanced somewhat, at least to the degree here, does not give rise
to constitutional problems. Pp. 476 U. S.
234 -239.

															749 F.2d 307, affirmed.

															BURGER, C.J., delivered the opinion of the Court, in which
WHITE, REHNQUIST, STEVENS, and O'CONNOR, JJ., joined, and in Part
III of which BRENNAN, MARSHALL, BLACKMUN, and POWELL, JJ., joined.
POWELL, J., filed an opinion concurring in part and dissenting in
part, in which BRENNAN, MARSHALL, and BLACKMUN, JJ., joined, post, p. 476 U. S.
240 . Page 476 U. S. 229 CHIEF JUSTICE BURGER delivered the opinion of the Court.

															We granted certiorari to review the holding of the Court of
Appeals (a) that the Environmental Protection Agency's aerial
observation of petitioner's plant complex did not exceed EPA's
statutory investigatory authority, and (b) that EPA's aerial
photography of petitioner's 2,000-acre plant complex without a
warrant was not a search under the Fourth Amendment. I Petitioner Dow Chemical Co. operates a 2,000-acre facility
manufacturing chemicals at Midland, Michigan. The facility consists
of numerous covered buildings, with manufacturing equipment and
piping conduits located between the various buildings exposed to
visual observation from the air. At all times, Dow has maintained
elaborate security around the perimeter of the complex barring
ground-level public views of these areas. It also investigates any
low-level flights by aircraft over the facility. Dow has not
undertaken, however, to conceal all manufacturing equipment within
the complex from aerial views. Dow maintains that the cost of
covering its exposed equipment would be prohibitive.

															In early 1978, enforcement officials of EPA, with Dow's consent,
made an on-site inspection of two powerplants in this complex. A
subsequent EPA request for a second inspection, however, was
denied, and EPA did not thereafter seek an administrative search
warrant. Instead, EPA employed a commercial aerial photographer,
using a standard floor-mounted, precision aerial mapping camera, to
take photographs of the facility from altitudes of 12,000, 3,000,
and 1,200 feet. At all times, the aircraft was lawfully within
navigable airspace. See 49 U.S.C.App. § 1304; 14 CFR § 91.
79 (1985). Page 476 U. S. 230 EPA did not inform Dow of this aerial photography, but when Dow
became aware of it, Dow brought suit in the District Court,
alleging that EPA's action violated the Fourth Amendment and was
beyond EPA's statutory investigative authority. The District Court
granted Dow's motion for summary judgment on the ground that EPA
had no authority to take aerial photographs, and that doing so was
a search violating the Fourth Amendment. EPA was permanently
enjoined from taking aerial photographs of Dow's premises and from
disseminating, releasing, or copying the photographs already taken. 536 F.
Supp. 1355 (ED Mich.1982).

															The District Court accepted the parties' concession that EPA's
" quest for evidence'" was a "search," id. at 1358, and
limited its analysis to whether the search was unreasonable under Katz v. United States, 389 U. S. 347 (1967). Proceeding on the assumption that a search in Fourth
Amendment terms had been conducted, the court found that Dow
manifested an expectation of privacy in its exposed plant areas
because it intentionally surrounded them with buildings and other
enclosures. 536 F. Supp. at 1364-1366. The District Court held that this expectation of privacy was
reasonable, as reflected in part by trade secret protections
restricting Dow's commercial competitors from aerial photography of
these exposed areas. Id. at 1366-1369. The court
emphasized that use of "the finest precision aerial camera
available" permitted EPA to capture on film "a great deal more than
the human eye could ever see." Id. at 1367.

															The Court of Appeals reversed. 749 F.2d 307 (CA6 1984). It
recognized that Dow indeed had a subjective expectation of privacy
in certain areas from ground -level intrusions, but the
court was not persuaded that Dow had a subjective expectation of
being free from aerial surveillance, since Dow had taken
no precautions against such observation, in contrast to its
elaborate ground-level precautions. Id. at 313. The court
rejected the argument that it was not feasible to shield any of the
critical parts of the exposed plant areas from aerial surveys. Id. at 312-313. The Court of Appeals, Page 476 U. S. 231 however, did not explicitly reject the District Court's factual
finding as to Dow's subjective expectations.

															Accepting the District Court finding of Dow's privacy
expectation, the Court of Appeals held that it was not a reasonable
expectation

															"[w]hen the entity observed is a multibuilding complex, and the
area observed is the outside of these buildings and the spaces in
between the buildings." Id. at 313. Viewing Dow's facility to be more like the
"open field" in Oliver v. United States, 466 U.
S. 170 (1984), than a home or an office, it held that
the common law curtilage doctrine did not apply to a large
industrial complex of closed buildings connected by pipes,
conduits, and other exposed manufacturing equipment. 749 F.2d at
313-314. The Court of Appeals looked to "the peculiarly strong
concepts of intimacy, personal autonomy and privacy associated with
the home" as the basis for the curtilage protection. Id. at 314. The court did not view the use of sophisticated
photographic equipment by EPA as controlling.

															The Court of Appeals then held that EPA clearly acted within its
statutory powers even absent express authorization for aerial
surveillance, concluding that the delegation of general
investigative authority to EPA, similar to that of other law
enforcement agencies, was sufficient to support the use of aerial
photography. Id. at 315. II The photographs at issue in this case are essentially like those
commonly used in mapmaking. Any person with an airplane and an
aerial camera could readily duplicate them. In common with much
else, the technology of photography has changed in this century.
These developments have enhanced industrial processes, and indeed
all areas of life; they have also enhanced law enforcement
techniques. Whether they may be employed by competitors to
penetrate trade secrets is not a question presented in this case.
Governments do not generally seek to appropriate trade secrets of
the private Page 476 U. S. 232 sector, and the right to be free of appropriation of trade
secrets is protected by law.

															Dow nevertheless relies heavily on its claim that trade secret
laws protect it from any aerial photography of this industrial
complex by its competitors, and that this protection is relevant to
our analysis of such photography under the Fourth Amendment. That
such photography might be barred by state law with regard to
competitors, however, is irrelevant to the questions presented
here. State tort law governing unfair competition does not define
the limits of the Fourth Amendment. Cf. Oliver v. United
States, supra, (trespass law does not necessarily define
limits of Fourth Amendment). The Government is seeking these
photographs in order to regulate, not to compete with, Dow. If the
Government were to use the photographs to compete with Dow, Dow
might have a Fifth Amendment "taking" claim. Indeed, Dow alleged
such a claim in its complaint, but the District Court dismissed it
without prejudice. But even trade secret laws would not bar all
forms of photography of this industrial complex; rather, only
photography with an intent to use any trade secrets revealed by the
photographs may be proscribed. Hence, there is no prohibition of
photographs taken by a casual passenger on an airliner, or those
taken by a company producing maps for its mapmaking purposes.

															Dow claims first that EPA has no authority to use aerial
photography to implement its statutory authority for "site
inspection" under § 114(a) of the Clean Air Act, 42 U.S.C. §
7414(a); [ Footnote 1 ] second,
Dow claims EPA's use of aerial photography Page 476 U. S. 233 was a "search" of an area that, notwithstanding the large size
of the plant, was within an "industrial curtilage," rather than an
"open field," and that it had a reasonable expectation of privacy
from such photography protected by the Fourth Amendment. III Congress has vested in EPA certain investigatory and enforcement
authority, without spelling out precisely how this authority was to
be exercised in all the myriad circumstances that might arise in
monitoring matters relating to clean air and water standards. When
Congress invests an agency with enforcement and investigatory
authority, it is not necessary to identify explicitly each and
every technique that may be used in the course of executing the
statutory mission. Aerial observation authority, for example, is
not usually expressly extended to police for traffic control, but
it could hardly be thought necessary for a legislative body to tell
police that aerial observation could be employed for traffic
control of a metropolitan area, or to expressly authorize police to
send messages to ground highway patrols that a particular
over-the-road truck was traveling in excess of 55 miles per hour.
Common sense and ordinary human experience teach that traffic
violators are apprehended by observation.

															Regulatory or enforcement authority generally carries with it
all the modes of inquiry and investigation traditionally employed
or useful to execute the authority granted. Environmental standards
such as clean air and clean water cannot be enforced only in
libraries and laboratories, helpful as those institutions may
be.

															Under § 114(a)(2), the Clean Air Act provides that "upon
presentation of . . . credentials," EPA has a "right of entry to,
upon, or through any premises." 42 U.S.C. § 7414(a)(2)(A). Dow
argues this limited grant of authority to enter does not Page 476 U. S. 234 authorize any aerial observation. In particular, Dow argues that
unannounced aerial observation deprives Dow of its right to be
informed that an inspection will be made or has occurred, and its
right to claim confidentiality of the information contained in the
places to be photographed, as provided in §§ 114(a) and (c), 42
U.S.C. §§ 7414(a) and (c). It is not claimed that EPA has disclosed
any of the photographs outside the agency.

															Section 114(a), however, appears to expand, not restrict, EPA's
general powers to investigate. Nor is there any suggestion in the
statute that the powers conferred by this section are intended to
be exclusive. There is no claim that EPA is prohibited from taking
photographs from a ground-level location accessible to the general
public. EPA, as a regulatory and enforcement agency, needs no
explicit statutory provision to employ methods of observation
commonly available to the public at large: we hold that the use of
aerial observation and photography is within EPA's statutory
authority. [ Footnote 2 ] IV We turn now to Dow's contention that taking aerial photographs
constituted a search without a warrant, thereby violating Dow's
rights under the Fourth Amendment. In making this contention,
however, Dow concedes that a simple flyover with naked-eye
observation, or the taking of a photograph from a nearby hillside
overlooking such a facility, would give rise to no Fourth Amendment
problem.

															In California v. Ciraolo, ante p. 476 U. S. 207 ,
decided today, we hold that naked-eye aerial observation from an
altitude of Page 476 U. S. 235 1,000 feet of a backyard within the curtilage of a home does not
constitute a search under the Fourth Amendment.

															In the instant case, two additional Fourth Amendment claims are
presented: whether the common law "curtilage" doctrine encompasses
a large industrial complex such as Dow's, and whether photography
employing an aerial mapping camera is permissible in this context.
Dow argues that an industrial plant, even one occupying 2,000
acres, does not fall within the "open fields" doctrine of Oliver v. United States, but rather is an "industrial
curtilage" having constitutional protection equivalent to that of
the curtilage of a private home. Dow further contends that any
aerial photography of this "industrial curtilage" intrudes upon its
reasonable expectations of privacy. Plainly, a business
establishment or an industrial or commercial facility enjoys
certain protections under the Fourth Amendment. See Marshall v.
Barlow's, Inc., 436 U. S. 307 (1978); See v. City of Seattle, 387 U.
S. 541 (1967).

															Two lines of cases are relevant to the inquiry: the curtilage
doctrine and the "open fields" doctrine. The curtilage area
immediately surrounding a private house has long been given
protection as a place where the occupants have a reasonable and
legitimate expectation of privacy that society is prepared to
accept. See Ciraolo, supra. As the curtilage doctrine evolved to protect much the same kind
of privacy as that covering the interior of a structure, the
contrasting "open fields" doctrine evolved as well. From Hester
v. United States, 265 U. S. 57 (1924), to Oliver v. United States, 466 U.
S. 170 (1984), the Court has drawn a line as to what
expectations are reasonable in the open areas beyond the curtilage
of a dwelling:

															"open fields do not provide the setting for those intimate
activities that the [Fourth] Amendment is intended to shelter from
governmental interference or surveillance." Oliver, 466 U.S. at 466 U. S. 179 .
In Oliver, we held that

															"an individual may not legitimately demand privacy for
activities out of doors in fields, except in the area Page 476 U. S. 236 immediately surrounding the home." Id. at 466 U. S. 178 .
To fall within the "open fields" doctrine, the area "need be
neither open' nor a `field' as those terms are used in common
speech." Id. at 466 U. S. 180 ,
n. 11. Dow plainly has a reasonable, legitimate, and objective
expectation of privacy within the interior of its covered
buildings, and it is equally clear that expectation is one society
is prepared to observe. E.g., See v. City of Seattle,
supra. Moreover, it could hardly be expected that Dow would
erect a huge cover over a 2,000-acre tract. In contending that its
entire enclosed plant complex is an "industrial curtilage," Dow
argues that its exposed manufacturing facilities are analogous to
the curtilage surrounding a home, because it has taken every
possible step to bar access from ground level.

															The Court of Appeals held that whatever the limits of an
"industrial curtilage" barring ground -level intrusions
into Dow's private areas, the open areas exposed here were more
analogous to "open fields" than to a curtilage for purposes of
aerial observation. 749 F.2d at 312-314. In Oliver, the
Court described the curtilage of a dwelling as "the area to which
extends the intimate activity associated with the sanctity of a
man's home and the privacies of life.'" 466 U.S. at 466 U. S. 180 (quoting Boyd v. United States, 116 U.
S. 616 , 116 U. S. 630 (1886)). See California v. Ciraolo, supra. The intimate
activities associated with family privacy and the home and its
curtilage simply do not reach the outdoor areas or spaces between
structures and buildings of a manufacturing plant. Admittedly, Dow's enclosed plant complex, like the area in Oliver, does not fall precisely within the "open fields"
doctrine. The area at issue here can perhaps be seen as falling
somewhere between "open fields" and curtilage, but lacking some of
the critical characteristics of both. [ Footnote 3 ] Dow's inner Page 476 U. S. 237 manufacturing areas are elaborately secured to ensure they are
not open or exposed to the public from the ground. Any actual
physical entry by EPA into any enclosed area would raise
significantly different questions, because

															"[t]he businessman, like the occupant of a residence, has a
constitutional right to go about his business free from
unreasonable official entries upon his private commercial
property." See v. City of Seattle, supra, at 387 U. S. 543 .
The narrow issue raised by Dow's claim of search and seizure,
however, concerns aerial observation of a 2,000-acre outdoor
manufacturing facility without physical entry. [ Footnote 4 ]

															We pointed out in Donovan v. Dewey, 452 U.
S. 594 , 452 U. S.
598 -599 (1981), that the Government has "greater
latitude to conduct warrantless inspections of commercial property"
because

															"the expectation of privacy that the owner of commercial
property enjoys in such property differs significantly Page 476 U. S. 238 from the sanctity accorded an individual's home."

															We emphasized that, unlike a homeowner's interest in his
dwelling, "[t]he interest of the owner of commercial property is
not one in being free from any inspections." Id. at 452 U. S. 599 .
And with regard to regulatory inspections, we have held that
"[w]hat is observable by the public is observable, without a
warrant, by the Government inspector as well." Marshall v.
Barlow's, Inc., 436 U.S. at 436 U. S. 315 (footnote omitted). Oliver recognized that, in the open field context, "the
public and police lawfully may survey lands from the air." 466 U.S.
at 466 U. S. 179 (footnote omitted). Here, EPA was not employing some unique sensory
device that, for example, could penetrate the walls of buildings
and record conversations in Dow's plants, offices, or laboratories,
but rather a conventional, albeit precise, commercial camera
commonly used in mapmaking. The Government asserts it has not yet
enlarged the photographs to any significant degree, but Dow points
out that simple magnification permits identification of objects
such as wires as small as 1/2-inch in diameter.

															It may well be, as the Government concedes, that surveillance of
private property by using highly sophisticated surveillance
equipment not generally available to the public, such as satellite
technology, might be constitutionally proscribed absent a warrant.
But the photographs here are not so revealing of intimate details
as to raise constitutional concerns. Although they undoubtedly give
EPA more detailed information than naked-eye views, they remain
limited to an outline of the facility's buildings and equipment.
The mere fact that human vision is enhanced somewhat, at least to
the degree here, does not give rise to constitutional problems.
[ Footnote 5 ] Page 476 U. S. 239 An electronic device to penetrate walls or windows so as to hear
and record confidential discussions of chemical formulae or other
trade secrets would raise very different and far more serious
questions; other protections such as trade secret laws are
available to protect commercial activities from private
surveillance by competitors. [ Footnote 6 ]

															We conclude that the open areas of an industrial plant complex
with numerous plant structures spread over an area of 2,000 acres
are not analogous to the "curtilage" of a dwelling for purposes of
aerial surveillance; [ Footnote
7 ] such an industrial complex is more comparable to an open
field, and, as such, it is open to the view and observation of
persons in aircraft lawfully in the public airspace immediately
above or sufficiently near the area for the reach of cameras.

															We hold that the taking of aerial photographs of an industrial
plant complex from navigable airspace is not a search prohibited by
the Fourth Amendment. Affirmed. [ Footnote 1 ]

															Section 114(a)(2) provides:

															"(2) the Administrator or his authorized representative, upon
presentation of his credentials -- "

															"(A) shall have a right of entry to, upon, or through any
premises of such person or in which any records required to be
maintained under paragraph (1) of this section are located,
and"

															"(B) may at reasonable times have access to and copy any
records, inspect any monitoring equipment or method required under
paragraph (1), and sample any emissions which such person is
required to sample under paragraph (1)."

															[ Footnote 2 ]

															Assuming the Clean Air Act's explicit provisions for protecting
trade secrets obtained by EPA as the result of its investigative
efforts is somehow deemed inapplicable to the information obtained
here, see 42 U.S.C. § 7414(c), Dow's fear that EPA might
disclose trade secrets revealed in these photographs appears
adequately addressed by federal law prohibiting such disclosure
generally under the Trade Secrets Act. 18 U.S.C. § 1905, and the
Freedom of Information Act, 5 U.S.C. § 552(b)(4). See Chrysler
Corp. v. Brown, 441 U. S. 281 (1979).

															[ Footnote 3 ]

															In Oliver, we observed that,

															"for most homes, the boundaries of the curtilage will be clearly
marked; and the conception defining the curtilage -- as the area
around the home to which the activity of home life extends -- is a
familiar one easily understood from our daily experience."

															466 U.S. at 466 U. S. 182 ,
n. 12. While we did not attempt to definitively mark the boundaries
of what constitutes an open field, we noted that "[i]t is clear . .
. that the term open fields' may include any unoccupied or
undeveloped area outside of the curtilage." Id. at 466 U. S. 180 ,
n. 11. As Oliver recognized, the curtilage surrounding a
home is generally a well-defined, limited area. In stark contrast,
the areas for which Dow claims enhanced protection cover the
equivalent of a half-dozen family farms. [ Footnote 4 ]

															We find it important that this is not an area immediately
adjacent to a private home, where privacy expectations are most
heightened. Nor is this an area where Dow has made any effort to
protect against aerial surveillance. Contrary to the partial
dissent's understanding, post at 476 U. S.
241 -242, the Court of Appeals emphasized:

															"Dow did not take any precautions against aerial
intrusions, even though the plant was near an airport and within
the pattern of planes landing and taking off. If elaborate and
expensive measures for Found security show that Dow has an actual
expectation of privacy in ground security, as Dow argues, then
taking no measure for aerial security should say something
about its actual privacy expectation in being free from aerial
observation."

															749 F.2d 307, 312 (CA6 1984) (emphasis added). Simply keeping
track of the identification numbers of any planes flying overhead,
with a later followup to see if photographs were taken, does not
constitute a "procedur[e] designed to protect the facility from
aerial photography." Post at 476 U. S.
241 .

															[ Footnote 5 ]

															The partial dissent emphasizes Dow's claim that, under
magnification, power lines as small as 1/2-inch in diameter can be
observed. Post at 476 U. S. 243 . But a glance at the photographs in issue
shows that those power lines are observable only because of their
stark contrast with the snow-white background. No objects as small
as 1/2-inch in diameter such as a class ring, for example, are
recognizable, nor are there any identifiable human faces or secret
documents captured in such a fashion as to implicate more serious
privacy concerns. Fourth Amendment cases must be decided on the
facts of each case, not by extravagant generalizations.

															"[W]e have never held that potential, as opposed to actual,
invasions of privacy constitute searches for purposes of the Fourth
Amendment." United States v. Karo, 468 U.
S. 705 , 468 U. S. 712 (1984). On these facts, nothing in these photographs suggests that
any reasonable expectations of privacy have been infringed.

															[ Footnote 6 ]

															The partial dissent relies heavily on Dow's claim that aerial
photography of its facility is proscribed by trade secret laws. Post at 476 U. S.
248 -249, and n. 11. While such laws may protect against
use of photography by competitors in the same trade to advance
their commercial interests, in no manner do "those laws constitute
society's express determination" that all photography of
Dow's facility violates reasonable expectations of privacy. Post at 476 U. S. 249 .
No trade secret law cited to us by Dow proscribes the use of aerial
photography of Dow's facilities for law enforcement purposes, let
alone photography for private purposes unrelated to competition
such as mapmaking or simple amateur snapshots. See supra at 476 U. S.
232 .

															[ Footnote 7 ]

															Our holding here does not reach the issues raised by the Court
of Appeals for the Seventh Circuit's holding regarding a "business
curtilage" in United States v. Swart, 679 F.2d 698 (CA7
1982); that case involved actual physical entry onto the business
premises.

															JUSTICE POWELL, with whom JUSTICE BRENNAN, JUSTICE MARSHALL, and
JUSTICE BLACKMUN join, concurring in part, and dissenting in
part.

															The Fourth Amendment protects private citizens from arbitrary
surveillance by their Government. For nearly 20 years, this Court
has adhered to a standard that ensured that Fourth Amendment rights
would retain their vitality as technology expanded the Government's
capacity to commit unsuspected intrusions into private areas and
activities. Today, in the context of administrative aerial
photography of commercial premises, the Court retreats from that
standard. It holds that the photography was not a Fourth Amendment
"search" because it was not accompanied by a physical trespass and
because the equipment used was not the most highly sophisticated
form of technology available to the Government. Under this holding,
the existence of an asserted privacy interest apparently will be
decided solely by reference to the manner of surveillance used to
intrude on that interest. Such an inquiry will not protect Fourth
Amendment rights, but rather will permit their gradual decay as
technology advances. I Since the 1890's, petitioner Dow Chemical Company (Dow) has been
manufacturing chemicals at a facility in Midland, Michigan. Its
complex covers 2,000 acres, and contains a number of chemical
process plants. Many of these are "open-air" plants, with reactor
equipment, loading and storage facilities, transfer lines, and
motors located in the open areas between buildings. Dow claims that
the technology used in these plants constitutes confidential
business information, and that the design and configuration of the
equipment located there reveal details of Dow's secret
manufacturing processes. [ Footnote
2/1 ] Page 476 U. S. 241 Short of erecting a roof over the Midland complex, Dow has, as
the Court states, undertaken "elaborate" precautions to secure the
facility from unwelcome intrusions. Ante at 476 U. S. 229 .
In fact, Dow appears to have done everything commercially feasible
to protect the confidential business information and property
located within the borders of the facility. Security measures
include an 8-foot-high chain link fence completely surrounding the
facility that is guarded by security personnel and monitored by
closed-circuit television, alarm systems that are triggered by
unauthorized entry into the facility, motion detectors that
indicate movement of persons within restricted areas, a prohibition
on use of camera equipment by anyone other than authorized Dow
personnel, and a strict policy under which no photographs of the
facility may be taken or released without prior management review
and approval. [ Footnote 2/2 ] In
addition to these precautions, the open-air plants were placed
within the internal portion of the 2,000-acre complex to conceal
them from the view of members of the public outside the perimeter
fence.

															Dow's security program also includes procedures designed to
protect the facility from aerial photography. Dow has instructed
its employees that it is "concerned when other than commercial
passenger flights pass over the plant property." App. 14. When
"suspicious" overflights occur, such as where a plane makes several
passes over the facility, employees try to obtain the plane's
identification number and description. Page 476 U. S. 242 Working with personnel from the State Police and local airports,
Dow employees then locate the pilot to determine if he has
photographed the facility. If Dow learns that he has done so, Dow
takes steps to prevent dissemination of photographs that show
details of its proprietary technology. [ Footnote 2/3 ]

															The controversy underlying this litigation arose out of the
efforts of the Environmental Protection Agency (EPA) to check
emissions from the power houses located within Dow's Midland
complex for violations of federal air quality standards. After
making one ground-level inspection with Dow's consent, and
obtaining schematic drawings of the power houses from Dow, EPA
requested Dow's permission to conduct a second inspection during
which EPA proposed to photograph the facility. Dow objected to
EPA's decision to take photographs, and denied the request. EPA
then informed Dow that it was considering obtaining a search
warrant to gain entry to the plant. Inexplicably, EPA did not
follow that procedure, but instead hired a private firm to take
aerial photographs of the facility.

															Using a sophisticated aerial mapping camera, [ Footnote 2/4 ] this firm took approximately 75 color
photographs of various parts of Page 476 U. S. 243 the plant. The District Court found that

															"some of the photographs taken from directly above the plant at
1,200 feet are capable of enlargement to a scale of 1 inch equals
20 feet or greater, without significant loss of detail or
resolution. When enlarged in this manner, and viewed under
magnification, it is possible to discern equipment, pipes, and
power lines as small as 1/2-inch in diameter." 536 F.
Supp. 1355 , 1357 (ED Mich.1982) (emphasis in original).
Observation of these minute details is, as the District Court
found, "a near physical impossibility" from anywhere "but directly above " the complex. Ibid. (emphasis in
original). Because of the complicated details captured in the
photographs, the District Court concluded, "the camera saw a great
deal more than the human eye could ever see," even if the observer
was located directly above the facility. [ Footnote 2/5 ] Id. at 1367.

															Several weeks later, Dow learned about the EPA-authorized
overflight from an independent source. Dow filed this lawsuit,
alleging that the aerial photography was an unreasonable search
under the Fourth Amendment and constituted an inspection technique
outside the scope of EPA's authority under the Clean Air Act, 42
U.S.C. §§ 7413, 7414. [ Footnote
2/6 ] The District Court upheld Dow's position on both issues,
and entered a permanent injunction restraining EPA from conducting
future aerial surveillance and photography of the Midland facility.
The Court of Appeals for the Sixth Circuit reversed. 749 F.2d 307
(1984). It concluded that, while Dow had a reasonable expectation
of privacy with respect to Page 476 U. S. 244 ground-level intrusion into the enclosed buildings within its
facility, it did not have such an expectation with respect to
aerial observation and photography. [ Footnote 2/7 ] The court also held that EPA's use of
aerial photography did not exceed its authority under § 114 of the
Clean Air Act, 42 U.S.C. § 7414. We granted certiorari to review
both of these holdings. 472 U.S. 1007 (1985).

															The Court rejects Dow's constitutional claim on the ground
that

															"the taking of aerial photographs of an industrial plant complex
from navigable airspace is not a search prohibited by the Fourth
Amendment." Ante at 476 U. S. 239 .
[ Footnote 2/8 ] The Court does not
explicitly reject application of the reasonable expectation of
privacy standard of Katz v. United States, 389 U.
S. 347 (1967), in this context; nor does it explain how
its result squares with Katz and its progeny. Instead, the
Court relies on questionable assertions concerning the manner of
the surveillance, and on its conclusion that the Midland facility
more closely resembles an "open field" than it does the "curtilage"
of a private home. The Court's decision marks a drastic reduction
in the Fourth Amendment protections previously afforded to private
commercial premises under our decisions. Along with California
v. Ciraolo, ante p. 476 U. S. 207 ,
also decided today, the decision may signal a significant retreat
from the rationale of prior Fourth Amendment decisions. Page 476 U. S. 245 II Fourth Amendment protection of privacy interests in business
premises "is . . . based upon societal expectations that have deep
roots in the history of the Amendment." Oliver v. United
States, 466 U. S. 170 , 466 U. S. 178 ,
n. 8 (1984). In Marshall v. Barlow's, Inc., 436 U.
S. 307 (1978), we observed that the "particular
offensiveness" of the general warrant and writ of assistance, so
despised by the Framers of the Constitution, "was acutely felt by
the merchants and businessmen whose premises and products were
inspected" under their authority. Id. at 436 U. S. 311 .
Against that history, "it is untenable that the ban on warrantless
searches was not intended to shield places of business as well as
of residence." Id. at 436 U. S. 312 .
Our precedents therefore leave no doubt that proprietors of
commercial premises, including corporations, have the right to
conduct their business free from unreasonable official intrusion. See G. M. Leasing Corp. v. United States, 429 U.
S. 338 , 429 U. S. 353 (1977); See v. City of Seattle, 387 U.
S. 541 , 387 U. S. 543 (1967).

															In the context of administrative inspections of business
premises, the Court has recognized an exception to the Fourth
Amendment rule that warrantless searches of property not accessible
to members of the public are presumptively unreasonable. Since the
interest of the owner of commercial property is "in being free from unreasonable intrusions onto his property by agents of the
government," not in being free from any inspections whatsoever, the
Court has held that "the assurance of regularity provided by a
warrant may be unnecessary under certain inspection schemes." Donovan v. Dewey, 452 U. S. 594 , 452 U. S. 599 (1981) (emphasis in original). Thus, where Congress has made a
reasonable determination that a system of warrantless inspections
is necessary to enforce its regulatory purpose, and where

															"the federal regulatory presence is sufficiently comprehensive
and defined that the owner of commercial property cannot help but
be aware that his property will be subject to periodic inspections,
" Page 476 U. S. 246 warrantless inspections may be permitted. Id. at 452 U. S. 600 .
This exception does not apply here. The Government does not
contend, nor does the Court hold, that the Clean Air Act authorizes
a warrantless inspection program that adequately protects the
privacy interests of those whose premises are subject to
inspection.

															Instead, the Court characterizes our decisions in this area
simply as giving the Government " greater latitude to conduct
warrantless inspections of commercial property'" because privacy
interests in such property differ significantly from privacy
interests in the home. Ante at 476 U. S. 237 (citation omitted). This reasoning misunderstands the relevant
precedents. The exception we have recognized for warrantless
inspections, limited to pervasively regulated businesses, see
Donovan v. Dewey, supra; United States v. Biswell, 406 U. S. 311 (1972); Colonnade Catering Corp. v. United States, 397 U. S. 72 (1970), is not founded solely on the differences between the
premises occupied by such businesses and homes, or on a conclusion
that administrative inspections do not intrude on protected privacy
interests, and therefore do not implicate Fourth Amendment
concerns. Rather, the exception is based on a determination that
the reasonable expectation of privacy that the owner of a business
does enjoy may be adequately protected by the regulatory scheme
itself. Donovan v. Dewey, supra, at 452 U. S. 599 .
We have never held that warrantless intrusions on commercial
property generally are acceptable under the Fourth Amendment. On
the contrary, absent a sufficiently defined and regular program of
warrantless inspections, the Fourth Amendment's warrant requirement
is fully applicable in the commercial context. Marshall v.
Barlow's, Inc., supra, at 436 U. S.
312 -315, 436 U. S. 324 ; G.M. Leasing Corp. v. United States, supra, at 429 U. S. 358 ; See v. City of Seattle, supra, at 387 U. S.
543 -546. III Since our decision in Katz v. United States, the
question whether particular governmental conduct constitutes a Page 476 U. S. 247 Fourth Amendment "search" has turned on whether that conduct
intruded on a constitutionally protected expectation of privacy. Smith v. Maryland, 442 U. S. 735 (1979); United States v. United States District Court, 407 U. S. 297 (1972). In the context of governmental inspection of commercial
property, the Court has relied on the standard of Katz to
determine whether an inspection violated the Fourth Amendment
rights of the owner of the property. See Marshall v. Barlow's,
Inc., supra, at 436 U. S. 313 , 436 U. S. 315 .
Today, while purporting to consider the Fourth Amendment question
raised here under the rubric of Katz, the Court's analysis
of the issue ignores the heart of the Katz standard. A The Court correctly observes that Dow has an expectation of
privacy in the buildings located on the Midland property, and that
society is prepared to recognize that expectation as reasonable. Ante at 476 U. S. 236 .
Similarly, in view of the numerous security measures protecting the
entire Dow complex from intrusion on the ground, the Court properly
concludes that Dow has a reasonable expectation in being free from
such intrusion. Ante at 476 U. S.
236 -237. Turning to the issue presented in this case,
however, the Court erroneously states that the Fourth Amendment
protects Dow only from "actual physical entry" by the Government
"into any enclosed area." Ibid. This statement simply repudiates Katz. The reasonable
expectation of privacy standard was designed to ensure that the
Fourth Amendment continues to protect privacy in an era when
official surveillance can be accomplished without any physical
penetration of or proximity to the area under inspection. Writing
for the Court in Katz, Justice Stewart explained that
Fourth Amendment protections would mean little in our modern world
if the reach of the Amendment "turn[ed] upon the presence or
absence of a physical intrusion into any given enclosure." 389 U.S.
at 389 U. S. 353 .
Thus, the Court's observation that the aerial photography was not
accompanied by a physical trespass is irrelevant to the
analysis Page 476 U. S. 248 of the Fourth Amendment issue raised here, just as it was
irrelevant in Katz. Since physical trespass no longer
functions as a reliable proxy for intrusion on privacy, it is
necessary to determine if the surveillance, whatever its form,
intruded on a reasonable expectation that a certain activity or
area would remain private. B An expectation of privacy is reasonable for Fourth Amendment
purposes if it is rooted in a

															"source outside of the Fourth Amendment, either by reference to
concepts of real or personal property law or to understandings that
are recognized and permitted by society. [ Footnote 2/9 ]" Rakas v. Illinois, 439 U. S. 128 , 439 U. S.
143 -144, n. 12 (1978). Dow argues that, by enacting
trade secret laws, society has recognized that it has a legitimate
interest in preserving the privacy of the relevant portions of its
open-air plants. As long as Dow takes reasonable steps to protect
its secrets, the law should enforce its right against theft or
disclosure of those secrets. [ Footnote 2/10 ]

															As discussed above, our cases holding that Fourth Amendment
protections extend to business property have expressly relied on
our society's historical understanding that owners Page 476 U. S. 249 of such property have a legitimate interest in being free from
unreasonable governmental inspection. Marshall v. Barlow's,
Inc., 436 U.S. at 436 U. S.
311 -313; see Oliver v. United States, 466 U.S.
at 466 U. S. 178 ,
n. 8. Moreover, despite the Court's misconception of the nature of
Dow's argument concerning the laws protecting the trade secrets
within its open-air plants, [ Footnote
2/11 ] Dow plainly is correct to argue that those laws
constitute society's express determination that commercial entities
have a legitimate interest in the privacy of certain kinds of
property. Dow has taken every feasible step to protect information
claimed to constitute trade secrets from the public, and
particularly from its competitors. Accordingly, Dow has a
reasonable expectation of privacy in its commercial facility in the
sense required by the Fourth Amendment. EPA's conduct in this case
intruded on that expectation because the aerial photography
captured information that Dow had taken reasonable steps to
preserve as private. C In this case, the Court does not claim that Dow's expectation of
privacy is unreasonable because members of the public fly in
airplanes. Whatever the merits of this position in California
v. Ciraolo, ante p. 476 U. S. 207 , it
is inapplicable here, for it is not the case that "[a]ny member of
the public flying in this airspace who cared to glance down" could
have obtained the information captured by the aerial photography of
Dow's facility. California v. Ciraolo, ante at 476 U. S. 213 .
As the District Court expressly found, the camera used to
photograph the facility "saw a great deal more than the human eye
could Page 476 U. S. 250 ever see." [ Footnote 2/12 ] 536
F. Supp. at 1367. See supra at 476 U. S.
242 -243, and n. 5. Thus, the possibility of casual
observation by passengers on commercial or private aircraft
provides no support for the Court's rejection of Dow's privacy
interests.

															The Court nevertheless asserts that Dow has no constitutionally
protected privacy interests in its open-air facility because the
facility more closely resembles an "open field" than a "curtilage."
Of course, the Dow facility resembles neither. The purpose of the
curtilage doctrine is to identify the limited outdoor area closely
associated with a home. See Oliver v. United States,
supra, at 466 U. S. 180 .
The doctrine is irrelevant here since Dow makes no argument that
its privacy interests are equivalent to those in the home.
Moreover, the curtilage doctrine has never been held to constitute
a limit on Fourth Amendment protection. Yet, the Court applies the
doctrine, which affords heightened protection to homeowners, in a
manner that eviscerates the protection traditionally given to the
owner of commercial property. The Court offers no convincing
explanation for this application.

															Nor does the open field doctrine have a role to play in this
case. Open fields, as we held in Oliver, are places in
which people do not enjoy reasonable expectations of privacy, and
therefore are open to warrantless inspections from ground Page 476 U. S. 251 and air alike. Oliver v. United States, supra, at 466 U. S.
180 -181. Here, the Court concedes that Dow was
constitutionally protected against warrantless intrusion by the
Government on the ground. The complex bears no resemblance to an
open field, either in fact or within the meaning of our cases.

															The other basis for the Court's judgment -- assorted
observations concerning the technology used to photograph Dow's
plant -- is even less convincing. The Court notes that EPA did not
use "some unique sensory device that, for example, could penetrate
the walls of buildings and record conversations." Ante at 476 U. S. 238 .
Nor did EPA use "satellite technology" or another type of
"equipment not generally available to the public." Ibid. Instead, as the Court states, the surveillance was accomplished by
using "a conventional, albeit precise, commercial camera commonly
used in mapmaking." Ibid. These observations shed no light
on the antecedent question whether Dow had a reasonable expectation
of privacy. Katz measures Fourth Amendment rights by
reference to the privacy interests that a free society recognizes
as reasonable, not by reference to the method of surveillance used
in the particular case. If the Court's observations were to become
the basis of a new Fourth Amendment standard that would replace the
rule in Katz, privacy rights would be seriously at risk as
technological advances become generally disseminated and available
in our society. [ Footnote
2/13 ] Page 476 U. S. 252 IV I would reverse the decision of the Court of Appeals. EPA's
aerial photography penetrated into a private commercial enclave, an
area in which society has recognized that privacy interests
legitimately may be claimed. The photographs captured highly
confidential information that Dow had taken reasonable and
objective steps to preserve as private. Since the Clean Air Act
does not establish a defined and regular program of warrantless
inspections, see Marshall v. Barlow's, Inc., 436 U.
S. 307 (1978), EPA should have sought a warrant from a
neutral judicial officer. [ Footnote
2/14 ] The Court's holding that the warrantless photography does
not constitute an unreasonable search within the meaning of the
Fourth Amendment is based on the absence of any physical trespass
-- a theory disapproved in a line of cases beginning with the
decision in Katz v. United States. E.g., United States
v. United States District Court, 407 U.
S. 297 (1972). These cases have provided a sensitive and
reasonable means of preserving interests in privacy cherished by
our society. The Court's decision today cannot be reconciled with
our precedents or with the purpose of the Fourth Amendment.

															[ Footnote 2/1 ]

															The record establishes that Dow used the open-air design
primarily for reasons of safety. Dow determined that, if an
accident were to occur and hazardous chemicals were inadvertently
released, the concentration of toxic and explosive fumes within
enclosed plants would constitute an intolerable risk to employee
health and safety. Moreover, as the Court correctly observes, Dow
found that the cost of enclosing the facility would be prohibitive. Ante at 229, 236. The record reflects that the cost of
roofing just one of the open-air plants would have been
approximately $15 million in 1978. The record further shows that
enclosing the plants would greatly increase the cost of routine
maintenance. App. 74-75.

															[ Footnote 2/2 ]

															On these and other security measures protecting the Midland
facility, the District Court found that Dow has "spent at least
3.25 million dollars in each of the last ten years" preceding this
litigation. 536 F.
Supp. 1355 , 1365 (ED Mich 1982).

															[ Footnote 2/3 ]

															When Dow discovers that aerial photographs have been taken, it
requests the photographer to turn over the film. Dow then develops
the film and reviews the photographs. If the photographs depict
private business information, Dow retains them and the negatives.
In the event that the photographer refuses to cooperate, Dow
commences litigation to protect its trade secrets.

															[ Footnote 2/4 ]

															The District Court believed it was "important to an
understanding of this case to provide a description of the highly
effective equipment used" in photographing Dow's facility. Id. at 1357, n. 2. "The aircraft used was a twin engine
Beechcraft," which is "able to provide photographic stability,
fast mobility and flight endurance required for precision
photography.'" Ibid. (citation omitted). The camera
used "cost in excess of $22,000.00, and is described by the company
as the 'finest precision aerial camera available.' . . . The camera
was mounted to the floor inside the aircraft, and was capable of
taking several photographs in precise and rapid succession." Ibid. (citation omitted). This technique facilitates
stereoscopic examination, a type of examination that permits depth
perception.

															[ Footnote 2/5 ]

															As the District Court explained, when a person is "flying at
1,200 or 6,000 feet, [his] eye can discern only the basic sizes,
shapes, outlines, and colors of the objects blow." Id. at
1367. The aerial camera used in this case, on the other hand,
"successfully captured vivid images of Dow's plant which EPA could
later analyze under enlarged and magnified conditions." Ibid. [ Footnote 2/6 ]

															Dow also claimed that the aerial photography constituted a
"taking" of its property without due process of law in violation of
the Fifth Amendment. The District Court dismissed that claim
without prejudice, and it is not before us.

															[ Footnote 2/7 ]

															The Court of Appeals' holding rested in part on its erroneous
observation that Dow had taken no steps to protect its privacy from
aerial intrusions. See 749 F.2d at 312-313. Moreover, the
court apparently assumed that Dow would have to build some kind of
barrier against aerial observation in order to have an actual
expectation of privacy from aerial surveillance. Ibid. The
court did not explain the basis for this assumption or discuss why
it disagreed with the District Court's conclusion that commercial
overflights posed virtually no risk to Dow's privacy interests.

															[ Footnote 2/8 ]

															I agree with the Court's determination that the use of aerial
photography as an inspection technique, absent Fourth Amendment
constraints, does not exceed the scope of EPA's authority under the
Clean Air Act, 42 U.S.C. § 7414(a), and to this extent, I join Part
III of the Court's opinion.

															[ Footnote 2/9 ]

															Our decisions often use the words "reasonable" and "legitimate"
interchangeably to describe a privacy interest entitled to Fourth
Amendment protection. See California v. Ciraolo, ante at 476 U. S.
219 -220, n. 4 (POWELL, J., dissenting).

															[ Footnote 2/10 ]

															As the District Court observed:

															"Society has spoken in this area through Congress, the State
Legislatures, and the courts. Federal law, under the Trade Secrets
Act, 18 U.S.C. § 1905, makes it a crime for government employees to
disclose trade secret information. The Clean Air Act itself, in
Section 114(c), 42 U.S.C. § 7414(c), addresses this concern for
[proprietary] information. Moreover, EPA has adopted regulations
providing for protection of trade secrets. 40 CFR 2.201-2.309.
Michigan law, in addition to recognizing a tort action, also makes
it a crime to appropriate trade secrets, M.C.L.A. § 752.772, as
well as to invade one's privacy by means of surveillance. M.C.L.A.
§§ 750.539a-539b. These legislative and judicial pronouncements are
reflective of a societal acceptance of Dow's privacy expectation as
reasonable."

															536 F. Supp. at 1367.

															[ Footnote 2/11 ]

															Contrary to the Court's assertion, Dow does not claim that
Fourth Amendment protection of its facility is coextensive with the
scope of trade secret statutes. Ante at 476 U. S. 232 .
Rather, Dow argues that the existence of those statutes provides
support for its claim that society recognizes commercial privacy
interests as reasonable.

															[ Footnote 2/12 ]

															The Court disregards the fact that photographs taken by the
sophisticated camera used in this case can be significantly
enlarged without loss of acuity. As explained in 476
U.S. 227 fn2/4|>n. 4, supra, the technique used in
taking these pictures facilitates stereoscopic examination, which
provides the viewer of the photographs with depth perception.
Moreover, if the photographs were taken on transparent slides, they
could be projected on a large screen. These possibilities
illustrate the intrusive nature of aerial surveillance ignored by
the Court today. The only Fourth Amendment limitation on such
surveillance under today's decision apparently is based on the means of surveillance. The Court holds that Dow had no
reasonable expectation of privacy from surveillance accomplished by
means of a $22,000 mapping camera, but that it does have a
reasonable expectation of privacy from satellite surveillance and
photography. This type of distinction is heretofore wholly unknown
in Fourth Amendment jurisprudence.

															[ Footnote 2/13 ]

															With all respect, the Court's purported distinction -- for
purposes of Fourth Amendment analysis -- between degrees of
sophistication in surveillance equipment simply cannot be supported
in fact or by the reasoning of any prior Fourth Amendment decision
of this Court. The camera used by the firm hired by EPA is
described by the Court as a "conventional" camera commonly used in
mapmaking. Ante at 476 U. S. 238 .
The Court suggests, if not holds, that its decision would have been
different if EPA had used "satellite technology" or other equipment
not "available to the public." Ibid. But the camera used
in this case was highly sophisticated in terms of its capability to
reveal minute details of Dow's confidential technology and
equipment. The District Court found that the photographs revealed
details as "small as 1/2-inch in diameter." See supra at 476 U. S. 243 .
Satellite photography hardly could have been more informative about
Dow's technology. Nor are "members of the public" likely to
purchase $22,000 cameras.

															[ Footnote 2/14 ]

															Our cases have explained that an administrative agency need not
demonstrate "[p]robable cause in the criminal law sense" to obtain
a warrant to inspect property for compliance with a regulatory
scheme. Marshall v. Barlow's, Inc., 436 U.S. at 436 U. S. 320 .
Rather, an administrative warrant may issue

															"not only on specific evidence of an existing violation, but
also on a showing that 'reasonable legislative or administrative
standards for conducting an . . . inspection are satisfied with
respect to a particular [establishment].'" Ibid. (footnote omitted; quoting Camara v.
Municipal Court, 387 U. S. 523 , 387 U. S. 538 (1967)).

Summary:
Here is a summary of the case:

In Dow Chemical Co. v. United States, the Supreme Court ruled that the Environmental Protection Agency (EPA) did not violate the Fourth Amendment or exceed its statutory authority when it took aerial photographs of a chemical company's plant without a warrant. The Court held that aerial observation and photography are within the EPA's investigative powers and that the company had no reasonable expectation of privacy from aerial surveillance in lawful navigable airspace. The Court also noted that the EPA did not need an explicit statutory provision to employ methods of observation available to the public. Additionally, the Court rejected the argument that state trade secrets law or tort law governing unfair competition defined the limits of the Fourth Amendment.