(Slip Opinion) OCTOBER TERM, 2006 1 

Syllabus 

NOTE: Where it is feasible, a syllabus (headnote) will be released, as is

being done in connection with this case, at the time the opinion is issued.

The syllabus constitutes no part of the opinion of the Court but has been

prepared by the Reporter of Decisions for the convenience of the reader. 

See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337. 

SUPREME COURT OF THE UNITED STATES 

Syllabus 

MASSACHUSETTS ET AL. v. ENVIRONMENTAL PROTECTION AGENCY ET AL. 

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR 

THE DISTRICT OF COLUMBIA CIRCUIT 

No. 05–1120. Argued November 29, 2006—Decided April 2, 2007 

Based on respected scientific opinion that a well-documented rise in

global temperatures and attendant climatological and environmental 

changes have resulted from a significant increase in the atmospheric 

concentration of “greenhouse gases,” a group of private organizations 

petitioned the Environmental Protection Agency (EPA) to begin regulating the emissions of four such gases, including carbon dioxide, under §202(a)(1) of the Clean Air Act, which requires that the EPA

“shall by regulation prescribe . . . standards applicable to the emission of any air pollutant from any class . . . of new motor vehicles . . . 

which in [the EPA Administrator’s] judgment cause[s], or contribute[s] to, air pollution . . . reasonably . . . anticipated to endanger

public health or welfare,” 42 U. S. C. §7521(a)(1). The Act defines 

“air pollutant” to include “any air pollution agent . . . , including any 

physical, chemical . . . substance . . . emitted into . . . the ambient

air.” §7602(g). EPA ultimately denied the petition, reasoning that

(1) the Act does not authorize it to issue mandatory regulations to

address global climate change, and (2) even if it had the authority to

set greenhouse gas emission standards, it would have been unwise to

do so at that time because a causal link between greenhouse gases

and the increase in global surface air temperatures was not unequivocally established. The agency further characterized any EPA

regulation of motor-vehicle emissions as a piecemeal approach to climate change that would conflict with the President’s comprehensive 

approach involving additional support for technological innovation,

the creation of nonregulatory programs to encourage voluntary private-sector reductions in greenhouse gas emissions, and further research on climate change, and might hamper the President’s ability 
2 MASSACHUSETTS v. EPA 

Syllabus 

to persuade key developing nations to reduce emissions.

Petitioners, now joined by intervenor Massachusetts and other 

state and local governments, sought review in the D. C. Circuit. Although each of the three judges on the panel wrote separately, two of

them agreed that the EPA Administrator properly exercised his discretion in denying the rulemaking petition. One judge concluded that 

the Administrator’s exercise of “judgment” as to whether a pollutant

could “reasonably be anticipated to endanger public health or welfare,” §7521(a)(1), could be based on scientific uncertainty as well as

other factors, including the concern that unilateral U. S. regulation of 

motor-vehicle emissions could weaken efforts to reduce other countries’ greenhouse gas emissions. The second judge opined that petitioners had failed to demonstrate the particularized injury to them 

that is necessary to establish standing under Article III, but accepted

the contrary view as the law of the case and joined the judgment on

the merits as the closest to that which he preferred. The court therefore denied review. 

Held: 

1. Petitioners have standing to challenge the EPA’s denial of their

rulemaking petition. Pp. 12–23. 

(a) This case suffers from none of the defects that would preclude

it from being a justiciable Article III “Controvers[y].” See, e.g., Luther v. Borden, 7 How. 1. Moreover, the proper construction of a congressional statute is an eminently suitable question for federal-court

resolution, and Congress has authorized precisely this type of challenge to EPA action, see 42 U. S. C. §7607(b)(1). Contrary to EPA’s

argument, standing doctrine presents no insuperable jurisdictional 

obstacle here. To demonstrate standing, a litigant must show that it

has suffered a concrete and particularized injury that is either actual 

or imminent, that the injury is fairly traceable to the defendant, and

that a favorable decision will likely redress that injury. See Lujan v. 

Defenders of Wildlife, 504 U. S. 555, 560–561. However, a litigant to

whom Congress has “accorded a procedural right to protect his concrete interests,” id., at 573, n. 7—here, the right to challenge agency

action unlawfully withheld, §7607(b)(1)—“can assert that right without meeting all the normal standards for redressability and immediacy,” ibid. Only one petitioner needs to have standing to authorize 

review. See Rumsfeld v. Forum for Academic and Institutional 

Rights, Inc., 547 U. S. 47, 52, n. 2. Massachusetts has a special position and interest here. It is a sovereign State and not, as in Lujan, a 

private individual, and it actually owns a great deal of the territory 

alleged to be affected. The sovereign prerogatives to force reductions 

in greenhouse gas emissions, to negotiate emissions treaties with developing countries, and (in some circumstances) to exercise the police 
Cite as: 549 U. S. ____ (2007) 3 

Syllabus 

power to reduce motor-vehicle emissions are now lodged in the Federal Government. Because congress has ordered EPA to protect Massachusetts (among others) by prescribing applicable standards,

§7521(a)(1), and has given Massachusetts a concomitant procedural 

right to challenge the rejection of its rulemaking petition as arbitrary

and capricious, §7607(b)(1), petitioners’ submissions as they pertain

to Massachusetts have satisfied the most demanding standards of the 

adversarial process. EPA’s steadfast refusal to regulate greenhouse 

gas emissions presents a risk of harm to Massachusetts that is both

“actual” and “imminent,” Lujan, 504 U. S., at 560, and there is a 

“substantial likelihood that the judicial relief requested” will prompt

EPA to take steps to reduce that risk, Duke Power Co. v. Carolina 

Environmental Study Group, Inc., 438 U. S. 59, 79. Pp. 12–17.

(b) The harms associated with climate change are serious and 

well recognized. The Government’s own objective assessment of the 

relevant science and a strong consensus among qualified experts indicate that global warming threatens, inter alia, a precipitate rise in

sea levels, severe and irreversible changes to natural ecosystems, a 

significant reduction in winter snowpack with direct and important 

economic consequences, and increases in the spread of disease and 

the ferocity of weather events. That these changes are widely shared

does not minimize Massachusetts’ interest in the outcome of this litigation. See Federal Election Comm’n v. Akins, 524 U. S. 11, 24. According to petitioners’ uncontested affidavits, global sea levels rose

between 10 and 20 centimeters over the 20th century as a result of 

global warming and have already begun to swallow Massachusetts’ 

coastal land. Remediation costs alone, moreover, could reach hundreds of millions of dollars. Pp. 17–19. 

(c) Given EPA’s failure to dispute the existence of a causal connection between man-made greenhouse gas emissions and global

warming, its refusal to regulate such emissions, at a minimum, “contributes” to Massachusetts’ injuries. EPA overstates its case in arguing that its decision not to regulate contributes so insignificantly to

petitioners’ injuries that it cannot be haled into federal court, and 

that there is no realistic possibility that the relief sought would mitigate global climate change and remedy petitioners’ injuries, especially since predicted increases in emissions from China, India, and 

other developing nations will likely offset any marginal domestic decrease EPA regulation could bring about. Agencies, like legislatures,

do not generally resolve massive problems in one fell swoop, see Williamson v. Lee Optical of Okla., Inc., 348 U. S. 483, 489, but instead 

whittle away over time, refining their approach as circumstances

change and they develop a more nuanced understanding of how best

to proceed, cf. SEC v. Chenery Corp., 332 U. S. 194, 202–203. That a 
4 MASSACHUSETTS v. EPA 

Syllabus 

first step might be tentative does not by itself negate federal-court jurisdiction. And reducing domestic automobile emissions is hardly 

tentative. Leaving aside the other greenhouse gases, the record indicates that the U. S. transportation sector emits an enormous quantity

of carbon dioxide into the atmosphere. Pp. 20–21.

(d) While regulating motor-vehicle emissions may not by itself 

reverse global warming, it does not follow that the Court lacks jurisdiction to decide whether EPA has a duty to take steps to slow or reduce it. See Larson v. Valente, 456 U. S. 228, 243, n. 15. Because of 

the enormous potential consequences, the fact that a remedy’s effectiveness might be delayed during the (relatively short) time it takes

for a new motor-vehicle fleet to replace an older one is essentially irrelevant. Nor is it dispositive that developing countries are poised to

substantially increase greenhouse gas emissions: A reduction in domestic emissions would slow the pace of global emissions increases,

no matter what happens elsewhere. The Court attaches considerable 

significance to EPA’s espoused belief that global climate change must 

be addressed. Pp. 21–23. 

2. The scope of the Court’s review of the merits of the statutory issues is narrow. Although an agency’s refusal to initiate enforcement

proceedings is not ordinarily subject to judicial review, Heckler v. 

Chaney, 470 U. S. 821, there are key differences between nonenforcement and denials of rulemaking petitions that are, as in the present circumstances, expressly authorized. EPA concluded alternatively in its petition denial that it lacked authority under §7521(a)(1)

to regulate new vehicle emissions because carbon dioxide is not an

“air pollutant” under §7602, and that, even if it possessed authority,

it would decline to exercise it because regulation would conflict with

other administration priorities. Because the Act expressly permits 

review of such an action, §7607(b)(1), this Court “may reverse [it if it

finds it to be] arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law,” §7607(d)(9). Pp. 24–25.

3. Because greenhouse gases fit well within the Act’s capacious 

definition of “air pollutant,” EPA has statutory authority to regulate 

emission of such gases from new motor vehicles. That definition— 

which includes “any air pollution agent . . . , including any physical,

chemical, . . . substance . . . emitted into . . . the ambient air . . . ,” 

§7602(g) (emphasis added)—embraces all airborne compounds of 

whatever stripe. Moreover, carbon dioxide and other greenhouse

gases are undoubtedly “physical [and] chemical . . . substance[s].” 

Ibid. EPA’s reliance on postenactment congressional actions and deliberations it views as tantamount to a command to refrain from 

regulating greenhouse gas emissions is unavailing. Even if postenactment legislative history could shed light on the meaning of an 
Cite as: 549 U. S. ____ (2007) 5 

Syllabus 

otherwise-unambiguous statute, EPA identifies nothing suggesting

that Congress meant to curtail EPA’s power to treat greenhouse 

gases as air pollutants. The Court has no difficulty reconciling Congress’ various efforts to promote interagency collaboration and research to better understand climate change with the agency’s preexisting mandate to regulate “any air pollutant” that may endanger 

the public welfare. FDA v. Brown & Williamson Tobacco Corp., 529 

U. S. 120, 133, distinguished. Also unpersuasive is EPA’s argument

that its regulation of motor-vehicle carbon dioxide emissions would 

require it to tighten mileage standards, a job (according to EPA) that

Congress has assigned to the Department of Transportation. The 

fact that DOT’s mandate to promote energy efficiency by setting

mileage standards may overlap with EPA’s environmental responsibilities in no way licenses EPA to shirk its duty to protect the public

“health” and “welfare,” §7521(a)(1). Pp. 25–30.

4. EPA’s alternative basis for its decision—that even if it has statutory authority to regulate greenhouse gases, it would be unwise to do 

so at this time—rests on reasoning divorced from the statutory text. 

While the statute conditions EPA action on its formation of a “judgment,” that judgment must relate to whether an air pollutant

“cause[s], or contribute[s] to, air pollution which may reasonably be 

anticipated to endanger public health or welfare.” §7601(a)(1). Under 

the Act’s clear terms, EPA can avoid promulgating regulations only if 

it determines that greenhouse gases do not contribute to climate

change or if it provides some reasonable explanation as to why it

cannot or will not exercise its discretion to determine whether they 

do. It has refused to do so, offering instead a laundry list of reasons 

not to regulate, including the existence of voluntary Executive 

Branch programs providing a response to global warming and impairment of the President’s ability to negotiate with developing nations to reduce emissions. These policy judgments have nothing to do 

with whether greenhouse gas emissions contribute to climate change 

and do not amount to a reasoned justification for declining to form a

scientific judgment. Nor can EPA avoid its statutory obligation by

noting the uncertainty surrounding various features of climate 

change and concluding that it would therefore be better not to regulate at this time. If the scientific uncertainty is so profound that it 

precludes EPA from making a reasoned judgment, it must say so. 

The statutory question is whether sufficient information exists for it

to make an endangerment finding. Instead, EPA rejected the rulemaking petition based on impermissible considerations. Its action 

was therefore “arbitrary, capricious, or otherwise not in accordance

with law,” §7607(d)(9). On remand, EPA must ground its reasons for 

action or inaction in the statute. Pp. 30–32. 
6 MASSACHUSETTS v. EPA 

Syllabus 

415 F. 3d 50, reversed and remanded. 

STEVENS, J., delivered the opinion of the Court, in which KENNEDY, 

SOUTER, GINSBURG, and BREYER, JJ., joined. ROBERTS, C. J., filed a dissenting opinion, in which SCALIA, THOMAS, and ALITO, JJ., joined. 

SCALIA, J., filed a dissenting opinion, in which ROBERTS, C. J., and 

THOMAS and ALITO, JJ., joined. 
_________________ 

_________________ 

Cite as: 549 U. S. ____ (2007) 1 

Opinion of the Court 

NOTICE: This opinion is subject to formal revision before publication in the

preliminary print of the United States Reports. Readers are requested to

notify the Reporter of Decisions, Supreme Court of the United States, Washington, D. C. 20543, of any typographical or other formal errors, in order

that corrections may be made before the preliminary print goes to press. 

SUPREME COURT OF THE UNITED STATES 

No. 05–1120 

MASSACHUSETTS, ET AL., PETITIONERS v. ENVIRONMENTAL PROTECTION AGENCY ET AL. 

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF

APPEALS FOR THE DISTRICT OF COLUMBIA CIRCUIT

[April 2, 2007]

 JUSTICE STEVENS delivered the opinion of the Court. 

A well-documented rise in global temperatures has

coincided with a significant increase in the concentration

of carbon dioxide in the atmosphere. Respected scientists

believe the two trends are related. For when carbon dioxide is released into the atmosphere, it acts like the ceiling 

of a greenhouse, trapping solar energy and retarding the

escape of reflected heat. It is therefore a species—the

most important species—of a “greenhouse gas.” 

Calling global warming “the most pressing environmental challenge of our time,”1 a group of States,2 local 

governments,3 and private organizations,4 alleged in a 

—————— 

1Pet. for Cert. 22. 2California, Connecticut, Illinois, Maine, Massachusetts, New Jersey, 

New Mexico, New York, Oregon, Rhode Island, Vermont, and Washington. 3District of Columbia, American Samoa, New York City, and Baltimore. 4Center for Biological Diversity, Center for Food Safety, Conservation Law Foundation, Environmental Advocates, Environmental 

Defense, Friends of the Earth, Greenpeace, International Center for 

Technology Assessment, National Environmental Trust, Natural 

Resources Defense Council, Sierra Club, Union of Concerned Scientists, 

and U. S. Public Interest Research Group. 
2 MASSACHUSETTS v. EPA 

Opinion of the Court 

petition for certiorari that the Environmental Protection

Agency (EPA) has abdicated its responsibility under the 

Clean Air Act to regulate the emissions of four greenhouse 

gases, including carbon dioxide. Specifically, petitioners

asked us to answer two questions concerning the meaning

of §202(a)(1) of the Act: whether EPA has the statutory 

authority to regulate greenhouse gas emissions from new 

motor vehicles; and if so, whether its stated reasons for 

refusing to do so are consistent with the statute. 

In response, EPA, supported by 10 intervening States5 

and six trade associations,6 correctly argued that we may

not address those two questions unless at least one petitioner has standing to invoke our jurisdiction under Article III of the Constitution. Notwithstanding the serious

character of that jurisdictional argument and the absence 

of any conflicting decisions construing §202(a)(1), the

unusual importance of the underlying issue persuaded us 

to grant the writ. 548 U. S. __ (2006). 

I 

Section 202(a)(1) of the Clean Air Act, as added by Pub. 

L. 89–272, §101(8), 79 Stat. 992, and as amended by, inter 

alia, 84 Stat. 1690 and 91 Stat. 791, 42 U. S. C. §7521(a)(1), 

provides: 

“The [EPA] Administrator shall by regulation prescribe (and from time to time revise) in accordance

with the provisions of this section, standards applicable to the emission of any air pollutant from any class 

or classes of new motor vehicles or new motor vehicle 

engines, which in his judgment cause, or contribute

to, air pollution which may reasonably be anticipated 

—————— 

5Alaska, Idaho, Kansas, Michigan, Nebraska, North Dakota, Ohio, 

South Dakota, Texas, and Utah. 6Alliance of Automobile Manufacturers, National Automobile Dealers 

Association, Engine Manufacturers Association, Truck Manufacturers

Association, CO2 Litigation Group, and Utility Air Regulatory Group. 
Cite as: 549 U. S. ____ (2007) 3 

Opinion of the Court 

to endanger public health or welfare . . . .”7 

The Act defines “air pollutant” to include “any air pollution agent or combination of such agents, including any

physical, chemical, biological, radioactive . . . substance or 

matter which is emitted into or otherwise enters the ambient air.” §7602(g). “Welfare” is also defined broadly: 

among other things, it includes “effects on . . . weather . . .

and climate.” §7602(h).

When Congress enacted these provisions, the study of

climate change was in its infancy.8 In 1959, shortly after 

the U. S. Weather Bureau began monitoring atmospheric 

carbon dioxide levels, an observatory in Mauna Loa, Hawaii, recorded a mean level of 316 parts per million. This 

was well above the highest carbon dioxide concentration—

no more than 300 parts per million—revealed in the 

420,000-year-old ice-core record.9 By the time Congress 

—————— 

7The 1970 version of §202(a)(1) used the phrase “which endangers

the public health or welfare” rather than the more-protective “which

may reasonably be anticipated to endanger public health or welfare.” 

See §6(a) of the Clean Air Amendments of 1970, 84 Stat. 1690. Congress amended §202(a)(1) in 1977 to give its approval to the decision in 

Ethyl Corp. v. EPA, 541 F. 2d 1, 25 (CADC 1976) (en banc), which held

that the Clean Air Act “and common sense . . . demand regulatory

action to prevent harm, even if the regulator is less than certain that

harm is otherwise inevitable.” See §401(d)(1) of the Clean Air Act

Amendments of 1977, 91 Stat. 791; see also H. R. Rep. No. 95–294, 

p. 49 (1977). 8The Council on Environmental Quality had issued a report in 1970

concluding that “[m]an may be changing his weather.” Environmental 

Quality: The First Annual Report 93. Considerable uncertainty remained

in those early years, and the issue went largely unmentioned in the 

congressional debate over the enactment of the Clean Air Act. But see 

116 Cong. Rec. 32914 (1970) (statement of Sen. Boggs referring to

Council’s conclusion that “[a]ir pollution alters the climate and may

produce global changes in temperature”). 9See Intergovernmental Panel on Climate Change, Climate Change

2001: Synthesis Report, pp. 202–203 (2001). By drilling through thick 

Antarctic ice sheets and extracting “cores,” scientists can examine ice 
4 MASSACHUSETTS v. EPA 

Opinion of the Court 

drafted §202(a)(1) in 1970, carbon dioxide levels had 

reached 325 parts per million.10 

In the late 1970’s, the Federal Government began devoting serious attention to the possibility that carbon dioxide

emissions associated with human activity could provoke 

climate change. In 1978, Congress enacted the National 

Climate Program Act, 92 Stat. 601, which required the 

President to establish a program to “assist the Nation and 

the world to understand and respond to natural and maninduced climate processes and their implications,” id., §3.

President Carter, in turn, asked the National Research 

Council, the working arm of the National Academy of 

Sciences, to investigate the subject. The Council’s response was unequivocal: “If carbon dioxide continues to 

increase, the study group finds no reason to doubt that 

climate changes will result and no reason to believe that 

these changes will be negligible. . . . A wait-and-see policy 

may mean waiting until it is too late.”11 

Congress next addressed the issue in 1987, when it

enacted the Global Climate Protection Act, Title XI of Pub. 

L. 100–204, 101 Stat. 1407, note following 15 U. S. C. 

§2901. Finding that “manmade pollution—the release of 

carbon dioxide, chlorofluorocarbons, methane, and other 

trace gases into the atmosphere—may be producing a 

—————— 

from long ago and extract small samples of ancient air. That air can 

then be analyzed, yielding estimates of carbon dioxide levels. Ibid. 10A more dramatic rise was yet to come: In 2006, carbon dioxide levels reached 382 parts per million, see Dept. of Commerce, National 

Oceanic & Atmospheric Administration, Mauna Loa CO2 Monthly Mean

Data, www.esrl.noaa.gov/gmd/ccgg/trends/co2_mm_mlo.dat (all Internet

materials as visited Mar. 29, 2007, and available in Clerk of Court’s 

case file), a level thought to exceed the concentration of carbon dioxide 

in the atmosphere at any point over the past 20-million years. See 

Intergovernmental Panel on Climate Change, Technical Summary of 

Working Group I Report 39 (2001). 11Climate Research Board, Carbon Dioxide and Climate: A Scientific 

Assessment, p. vii (1979). 
Cite as: 549 U. S. ____ (2007) 5 

Opinion of the Court 

long-term and substantial increase in the average temperature on Earth,” §1102(1), 101 Stat. 1408, Congress

directed EPA to propose to Congress a “coordinated national policy on global climate change,” §1103(b), and 

ordered the Secretary of State to work “through the channels of multilateral diplomacy” and coordinate diplomatic 

efforts to combat global warming, §1103(c). Congress

emphasized that “ongoing pollution and deforestation may 

be contributing now to an irreversible process” and that 

“[n]ecessary actions must be identified and implemented 

in time to protect the climate.” §1102(4).

Meanwhile, the scientific understanding of climate 

change progressed. In 1990, the Intergovernmental Panel 

on Climate Change (IPCC), a multinational scientific body 

organized under the auspices of the United Nations, published its first comprehensive report on the topic. Drawing on expert opinions from across the globe, the IPCC

concluded that “emissions resulting from human activities

are substantially increasing the atmospheric concentrations of . . . greenhouse gases [which] will enhance the 

greenhouse effect, resulting on average in an additional 

warming of the Earth’s surface.”12 

Responding to the IPCC report, the United Nations

convened the “Earth Summit” in 1992 in Rio de Janeiro. 

The first President Bush attended and signed the United

Nations Framework Convention on Climate Change

(UNFCCC), a nonbinding agreement among 154 nations to 

reduce atmospheric concentrations of carbon dioxide and

other greenhouse gases for the purpose of “prevent[ing] 

dangerous anthropogenic [i.e., human-induced] interference with the [Earth’s] climate system.”13 S. Treaty Doc. 

—————— 

12 IPCC, Climate Change: The IPCC Scientific Assessment, p. xi (J. 

Houghton, G. Jenkins, & J. Ephraums eds. 1991). 13The industrialized countries listed in Annex I to the UNFCCC undertook to reduce their emissions of greenhouse gases to 1990 levels by

the year 2000. No immediate restrictions were imposed on developing 
6 MASSACHUSETTS v. EPA 

Opinion of the Court 

No. 102–38, Art. 2, p. 5 (1992). The Senate unanimously 

ratified the treaty.

Some five years later—after the IPCC issued a second

comprehensive report in 1995 concluding that “[t]he balance of evidence suggests there is a discernible human

influence on global climate”14—the UNFCCC signatories 

met in Kyoto, Japan, and adopted a protocol that assigned

mandatory targets for industrialized nations to reduce 

greenhouse gas emissions. Because those targets did not 

apply to developing and heavily polluting nations such as

China and India, the Senate unanimously passed a resolution expressing its sense that the United States should not 

enter into the Kyoto Protocol. See S. Res. 98, 105th Cong.,

1st Sess. (July 25, 1997) (as passed). President Clinton did 

not submit the protocol to the Senate for ratification. 

II 

On October 20, 1999, a group of 19 private organizations15 filed a rulemaking petition asking EPA to regulate

“greenhouse gas emissions from new motor vehicles under 

§202 of the Clean Air Act.” App. 5. Petitioners maintained that 1998 was the “warmest year on record”; that 

carbon dioxide, methane, nitrous oxide, and hydrofluorocarbons are “heat trapping greenhouse gases”; that green-

—————— 

countries, including China and India. They could choose to become 

Annex I countries when sufficiently developed. 14 IPCC, Climate Change 1995, The Science of Climate Change, p. 4. 15Alliance for Sustainable Communities; Applied Power Technologies,

Inc.; Bio Fuels America; The California Solar Energy Industries Assn.; 

Clements Environmental Corp.; Environmental Advocates; Environmental and Energy Study Institute; Friends of the Earth; Full Circle 

Energy Project, Inc.; The Green Party of Rhode Island; Greenpeace

USA; International Center for Technology Assessment; Network for 

Environmental and Economic Responsibility of the United Church of

Christ; New Jersey Environmental Watch; New Mexico Solar Energy

Assn.; Oregon Environmental Council; Public Citizen; Solar Energy

Industries Assn.; The SUN DAY Campaign. See App. 7–11. 
Cite as: 549 U. S. ____ (2007) 7 

Opinion of the Court 

house gas emissions have significantly accelerated climate

change; and that the IPCC’s 1995 report warned that

“carbon dioxide remains the most important contributor to

[man-made] forcing of climate change.” Id., at 13 (internal

quotation marks omitted). The petition further alleged

that climate change will have serious adverse effects on

human health and the environment. Id., at 22–35. As to 

EPA’s statutory authority, the petition observed that the 

agency itself had already confirmed that it had the power 

to regulate carbon dioxide. See id., at 18, n. 21. In 1998, 

Jonathan Z. Cannon, then EPA’s General Counsel, prepared a legal opinion concluding that “CO2 emissions are 

within the scope of EPA’s authority to regulate,” even as 

he recognized that EPA had so far declined to exercise 

that authority. Id., at 54 (memorandum to Carol M. 

Browner, Administrator (Apr. 10, 1998) (hereinafter Cannon memorandum)). Cannon’s successor, Gary S. Guzy,

reiterated that opinion before a congressional committee 

just two weeks before the rulemaking petition was filed.

See id., at 61. 

Fifteen months after the petition’s submission, EPA

requested public comment on “all the issues raised in [the] 

petition,” adding a “particular” request for comments on

“any scientific, technical, legal, economic or other aspect of 

these issues that may be relevant to EPA’s consideration 

of this petition.” 66 Fed. Reg. 7486, 7487 (2001). EPA 

received more than 50,000 comments over the next five 

months. See 68 Fed. Reg. 52924 (2003).

Before the close of the comment period, the White House

sought “assistance in identifying the areas in the science 

of climate change where there are the greatest certainties 

and uncertainties” from the National Research Council, 

asking for a response “as soon as possible.” App. 213. The 

result was a 2001 report titled Climate Change: An Analysis 

of Some Key Questions (NRC Report), which, drawing heavily on the 1995 IPCC report, concluded that “[g]reenhouse 
8 MASSACHUSETTS v. EPA 

Opinion of the Court 

gases are accumulating in Earth’s atmosphere as a result

of human activities, causing surface air temperatures and 

subsurface ocean temperatures to rise. Temperatures are,

in fact, rising.” NRC Report 1. 

On September 8, 2003, EPA entered an order denying the

rulemaking petition. 68 Fed. Reg. 52922. The agency gave

two reasons for its decision: (1) that contrary to the opinions of its former general counsels, the Clean Air Act does

not authorize EPA to issue mandatory regulations to 

address global climate change, see id., at 52925–52929; 

and (2) that even if the agency had the authority to set

greenhouse gas emission standards, it would be unwise to

do so at this time, id., at 52929–52931. 

In concluding that it lacked statutory authority over 

greenhouse gases, EPA observed that Congress “was well 

aware of the global climate change issue when it last 

comprehensively amended the [Clean Air Act] in 1990,” 

yet it declined to adopt a proposed amendment establishing binding emissions limitations. Id., at 52926. Congress

instead chose to authorize further investigation into climate change. Ibid. (citing §§103(g) and 602(e) of the 

Clean Air Act Amendments of 1990, 104 Stat. 2652, 2703, 

42 U. S. C. §§7403(g)(1) and 7671a(e)). EPA further reasoned that Congress’ “specially tailored solutions to global 

atmospheric issues,” 68 Fed. Reg. 52926—in particular, its 

1990 enactment of a comprehensive scheme to regulate 

pollutants that depleted the ozone layer, see Title VI, 104 

Stat. 2649, 42 U. S. C. §§7671–7671q—counseled against 

reading the general authorization of §202(a)(1) to confer 

regulatory authority over greenhouse gases. 

EPA stated that it was “urged on in this view” by this

Court’s decision in FDA v. Brown & Williamson Tobacco 

Corp., 529 U. S. 120 (2000). In that case, relying on “tobacco[’s] unique political history,” id., at 159, we invalidated the Food and Drug Administration’s reliance on its 

general authority to regulate drugs as a basis for asserting 
Cite as: 549 U. S. ____ (2007) 9 

Opinion of the Court 

jurisdiction over an “industry constituting a significant

portion of the American economy,” ibid. 

EPA reasoned that climate change had its own “political

history”: Congress designed the original Clean Air Act to 

address local air pollutants rather than a substance that 

“is fairly consistent in its concentration throughout the 

world’s atmosphere,” 68 Fed. Reg. 52927 (emphasis

added); declined in 1990 to enact proposed amendments to 

force EPA to set carbon dioxide emission standards for 

motor vehicles, ibid. (citing H. R. 5966, 101st Cong., 2d

Sess. (1990)); and addressed global climate change in

other legislation, 68 Fed. Reg. 52927. Because of this 

political history, and because imposing emission limitations on greenhouse gases would have even greater economic and political repercussions than regulating tobacco, 

EPA was persuaded that it lacked the power to do so. Id., 

at 52928. In essence, EPA concluded that climate change

was so important that unless Congress spoke with exacting specificity, it could not have meant the agency to

address it. 

Having reached that conclusion, EPA believed it followed that greenhouse gases cannot be “air pollutants” 

within the meaning of the Act. See ibid. (“It follows from

this conclusion, that [greenhouse gases], as such, are not 

air pollutants under the [Clean Air Act’s] regulatory provisions . . .”). The agency bolstered this conclusion by

explaining that if carbon dioxide were an air pollutant, the

only feasible method of reducing tailpipe emissions would 

be to improve fuel economy. But because Congress has

already created detailed mandatory fuel economy standards subject to Department of Transportation (DOT)

administration, the agency concluded that EPA regulation

would either conflict with those standards or be superfluous. Id., at 52929. 

Even assuming that it had authority over greenhouse

gases, EPA explained in detail why it would refuse to exer-
10 MASSACHUSETTS v. EPA 

Opinion of the Court 

cise that authority. The agency began by recognizing that 

the concentration of greenhouse gases has dramatically

increased as a result of human activities, and acknowledged

the attendant increase in global surface air temperatures. 

Id., at 52930. EPA nevertheless gave controlling importance to the NRC Report’s statement that a causal link

between the two “‘cannot be unequivocally established.’” 

Ibid. (quoting NRC Report 17). Given that residual uncertainty, EPA concluded that regulating greenhouse gas 

emissions would be unwise. 68 Fed. Reg. 52930. 

The agency furthermore characterized any EPA regulation of motor-vehicle emissions as a “piecemeal approach” to

climate change, id., at 52931, and stated that such regulation would conflict with the President’s “comprehensive 

approach” to the problem, id., at 52932. That approach 

involves additional support for technological innovation, the 

creation of nonregulatory programs to encourage voluntary

private-sector reductions in greenhouse gas emissions, and 

further research on climate change—not actual regulation. 

Id., at 52932–52933. According to EPA, unilateral EPA 

regulation of motor-vehicle greenhouse gas emissions might 

also hamper the President’s ability to persuade key developing countries to reduce greenhouse gas emissions. Id., at 

52931. 

III 

Petitioners, now joined by intervenor States and local 

governments, sought review of EPA’s order in the United 

States Court of Appeals for the District of Columbia Circuit.16 Although each of the three judges on the panel

wrote a separate opinion, two judges agreed “that the EPA 

—————— 

16See 42 U. S. C. §7607(b)(1) (“A petition for review of action of the 

Administrator in promulgating any . . . standard under section 7521 of 

this title . . . or final action taken, by the Administrator under this

chapter may be filed only in the United States Court of Appeals for the 

District of Columbia”). 
Cite as: 549 U. S. ____ (2007) 11 

Opinion of the Court 

Administrator properly exercised his discretion under 

§202(a)(1) in denying the petition for rule making.” 415 F. 

3d 50, 58 (2005). The court therefore denied the petition

for review. 

In his opinion announcing the court’s judgment, Judge

Randolph avoided a definitive ruling as to petitioners’

standing, id., at 56, reasoning that it was permissible to

proceed to the merits because the standing and the merits

inquiries “overlap[ped],” ibid. Assuming without deciding 

that the statute authorized the EPA Administrator to 

regulate greenhouse gas emissions that “in his judgment” 

may “reasonably be anticipated to endanger public health 

or welfare,” 42 U. S. C. §7521(a)(1), Judge Randolph concluded that the exercise of that judgment need not be

based solely on scientific evidence, but may also be informed by the sort of policy judgments that motivate

congressional action. 415 F. 3d, at 58. Given that framework, it was reasonable for EPA to base its decision on 

scientific uncertainty as well as on other factors, including 

the concern that unilateral regulation of U. S. motorvehicle emissions could weaken efforts to reduce greenhouse gas emissions from other countries. Ibid. 

Judge Sentelle wrote separately because he believed 

petitioners failed to “demonstrat[e] the element of injury

necessary to establish standing under Article III.” Id., at 

59 (opinion dissenting in part and concurring in judgment). In his view, they had alleged that global warming 

is “harmful to humanity at large,” but could not allege 

“particularized injuries” to themselves. Id., at 60 (citing 

Lujan v. Defenders of Wildlife, 504 U. S. 555, 562 (1992)). 

While he dissented on standing, however, he accepted the 

contrary view as the law of the case and joined Judge 

Randolph’s judgment on the merits as the closest to that

which he preferred. 415 F. 3d, at 60–61. 

Judge Tatel dissented. Emphasizing that EPA nowhere

challenged the factual basis of petitioners’ affidavits, id., 
12 MASSACHUSETTS v. EPA 

Opinion of the Court 

at 66, he concluded that at least Massachusetts had “satisfied each element of Article III standing—injury, causation, and redressability,” id., at 64. In Judge Tatel’s view,

the “‘substantial probability,’” id., at 66, that projected 

rises in sea level would lead to serious loss of coastal 

property was a “far cry” from the kind of generalized harm 

insufficient to ground Article III jurisdiction. Id., at 65. 

He found that petitioners’ affidavits more than adequately 

supported the conclusion that EPA’s failure to curb greenhouse gas emissions contributed to the sea level changes

that threatened Massachusetts’ coastal property. Ibid. As 

to redressability, he observed that one of petitioners’ 

experts, a former EPA climatologist, stated that 

“‘[a]chievable reductions in emissions of CO2 and other 

[greenhouse gases] from U. S. motor vehicles would . . . 

delay and moderate many of the adverse impacts of global 

warming.’” Ibid. (quoting declaration of Michael MacCracken, former Executive Director, U. S. Global Change

Research Program ¶5(e) (hereinafter MacCracken Decl.),

available in 2 Petitioners’ Standing Appendix in No. 03–

1361, etc., (CADC), p. 209 (Stdg. App.)). He further noted 

that the one-time director of EPA’s motor-vehicle pollution

control efforts stated in an affidavit that enforceable emission standards would lead to the development of new

technologies that “‘would gradually be mandated by other 

countries around the world.’” 415 F. 3d, at 66 (quoting 

declaration of Michael Walsh ¶¶7–8, 10, Stdg. App. 309–

310, 311). On the merits, Judge Tatel explained at length

why he believed the text of the statute provided EPA with 

authority to regulate greenhouse gas emissions, and why 

its policy concerns did not justify its refusal to exercise

that authority. 415 F. 3d, at 67–82. 

IV 

Article III of the Constitution limits federal-court jurisdiction to “Cases” and “Controversies.” Those two words 
Cite as: 549 U. S. ____ (2007) 13 

Opinion of the Court 

confine “the business of federal courts to questions presented in an adversary context and in a form historically 

viewed as capable of resolution through the judicial process.” Flast v. Cohen, 392 U. S. 83, 95 (1968). It is therefore familiar learning that no justiciable “controversy” 

exists when parties seek adjudication of a political question, Luther v. Borden, 7 How. 1 (1849), when they ask for 

an advisory opinion, Hayburn’s Case, 2 Dall. 409 (1792), 

see also Clinton v. Jones, 520 U. S. 681, 700, n. 33 (1997), 

or when the question sought to be adjudicated has been

mooted by subsequent developments, California v. San 

Pablo & Tulare R. Co., 149 U. S. 308 (1893). This case 

suffers from none of these defects. 

The parties’ dispute turns on the proper construction of a 

congressional statute, a question eminently suitable to 

resolution in federal court. Congress has moreover authorized this type of challenge to EPA action. See 42 U. S. C. 

§7607(b)(1). That authorization is of critical importance to

the standing inquiry: “Congress has the power to define

injuries and articulate chains of causation that will give 

rise to a case or controversy where none existed before.” 

Lujan, 504 U. S., at 580 (KENNEDY, J., concurring in part 

and concurring in judgment). “In exercising this power,

however, Congress must at the very least identify the

injury it seeks to vindicate and relate the injury to the 

class of persons entitled to bring suit.” Ibid. We will not, 

therefore, “entertain citizen suits to vindicate the public’s

nonconcrete interest in the proper administration of the 

laws.” Id., at 581. 

EPA maintains that because greenhouse gas emissions 

inflict widespread harm, the doctrine of standing presents

an insuperable jurisdictional obstacle. We do not agree.

At bottom, “the gist of the question of standing” is whether

petitioners have “such a personal stake in the outcome of

the controversy as to assure that concrete adverseness 

which sharpens the presentation of issues upon which the 
14 MASSACHUSETTS v. EPA 

Opinion of the Court 

court so largely depends for illumination.” Baker v. Carr, 

369 U. S. 186, 204 (1962). As JUSTICE KENNEDY explained

in his Lujan concurrence: 

“While it does not matter how many persons have 

been injured by the challenged action, the party bringing suit must show that the action injures him in a 

concrete and personal way. This requirement is not 

just an empty formality. It preserves the vitality of

the adversarial process by assuring both that the parties before the court have an actual, as opposed to professed, stake in the outcome, and that the legal questions presented . . . will be resolved, not in the rarified 

atmosphere of a debating society, but in a concrete 

factual context conducive to a realistic appreciation of 

the consequences of judicial action.” 504 U. S., at 581 

(internal quotation marks omitted). 

To ensure the proper adversarial presentation, Lujan

holds that a litigant must demonstrate that it has suffered

a concrete and particularized injury that is either actual

or imminent, that the injury is fairly traceable to the

defendant, and that it is likely that a favorable decision

will redress that injury. See id., at 560–561. However, a 

litigant to whom Congress has “accorded a procedural

right to protect his concrete interests,” id., at 572, n. 7— 

here, the right to challenge agency action unlawfully

withheld, §7607(b)(1)—“can assert that right without 

meeting all the normal standards for redressability and 

immediacy,” ibid. When a litigant is vested with a procedural right, that litigant has standing if there is some

possibility that the requested relief will prompt the injurycausing party to reconsider the decision that allegedly 

harmed the litigant. Ibid.; see also Sugar Cane Growers 

Cooperative of Fla. v. Veneman, 289 F. 3d 89, 94–95 

(CADC 2002) (“A [litigant] who alleges a deprivation of a

procedural protection to which he is entitled never has to 
Cite as: 549 U. S. ____ (2007) 15 

Opinion of the Court 

prove that if he had received the procedure the substantive result would have been altered. All that is necessary 

is to show that the procedural step was connected to the 

substantive result”).

Only one of the petitioners needs to have standing to

permit us to consider the petition for review. See Rumsfeld 

v. Forum for Academic and Institutional Rights, Inc., 547 

U. S. 47, 52, n. 2 (2006). We stress here, as did Judge Tatel

below, the special position and interest of Massachusetts.

It is of considerable relevance that the party seeking review here is a sovereign State and not, as it was in Lujan, 

a private individual. 

Well before the creation of the modern administrative 

state, we recognized that States are not normal litigants

for the purposes of invoking federal jurisdiction. As Justice Holmes explained in Georgia v. Tennessee Copper Co., 

206 U. S. 230, 237 (1907), a case in which Georgia sought 

to protect its citizens from air pollution originating outside

its borders: 

“The case has been argued largely as if it were one

between two private parties; but it is not. The very

elements that would be relied upon in a suit between

fellow-citizens as a ground for equitable relief are 

wanting here. The State owns very little of the territory alleged to be affected, and the damage to it capable of estimate in money, possibly, at least, is small.

This is a suit by a State for an injury to it in its capacity of quasi-sovereign. In that capacity the State has

an interest independent of and behind the titles of its 

citizens, in all the earth and air within its domain. It 

has the last word as to whether its mountains shall be 

stripped of their forests and its inhabitants shall 

breathe pure air.” 

Just as Georgia’s “independent interest . . . in all the earth

and air within its domain” supported federal jurisdiction a 
16 MASSACHUSETTS v. EPA 

Opinion of the Court 

century ago, so too does Massachusetts’ well-founded 

desire to preserve its sovereign territory today. Cf. Alden 

v. Maine, 527 U. S. 706, 715 (1999) (observing that in the 

federal system, the States “are not relegated to the role of

mere provinces or political corporations, but retain the 

dignity, though not the full authority, of sovereignty”).

That Massachusetts does in fact own a great deal of the

“territory alleged to be affected” only reinforces the conclusion that its stake in the outcome of this case is sufficiently concrete to warrant the exercise of federal judicial 

power.

When a State enters the Union, it surrenders certain 

sovereign prerogatives. Massachusetts cannot invade 

Rhode Island to force reductions in greenhouse gas emissions, it cannot negotiate an emissions treaty with China

or India, and in some circumstances the exercise of its 

police powers to reduce in-state motor-vehicle emissions 

might well be pre-empted. See Alfred L. Snapp & Son, 

Inc. v. Puerto Rico ex rel. Barez, 458 U. S. 592, 607 (1982) 

(“One helpful indication in determining whether an alleged injury to the health and welfare of its citizens suffices to give the State standing to sue parens patriae is 

whether the injury is one that the State, if it could, would 

likely attempt to address through its sovereign lawmaking 

powers”).

These sovereign prerogatives are now lodged in the

Federal Government, and Congress has ordered EPA to

protect Massachusetts (among others) by prescribing standards applicable to the “emission of any air pollutant from

any class or classes of new motor vehicle engines, which in

[the Administrator’s] judgment cause, or contribute to, air

pollution which may reasonably be anticipated to endanger

public health or welfare.” 42 U. S. C. §7521(a)(1). Congress has moreover recognized a concomitant procedural

right to challenge the rejection of its rulemaking petition

as arbitrary and capricious. §7607(b)(1). Given that pro-
Cite as: 549 U. S. ____ (2007) 17 

Opinion of the Court 

cedural right and Massachusetts’ stake in protecting its

quasi-sovereign interests, the Commonwealth is entitled to

special solicitude in our standing analysis.17 

—————— 

17 THE CHIEF JUSTICE accuses the Court of misreading Georgia v. Tennessee Copper Co., 206 U. S. 230 (1907), see post, at 3–4 (dissenting

opinion), and “devis[ing] a new doctrine of state standing,” id., at 15. 

But no less an authority than Hart & Wechsler’s The Federal Courts 

and the Federal System understands Tennessee Copper as a standing 

decision. R. Fallon, D. Meltzer, & D. Shapiro, Hart & Wechsler’s The 

Federal Courts and the Federal System 290 (5th ed. 2003). Indeed, it 

devotes an entire section to chronicling the long development of cases 

permitting States “to litigate as parens patriae to protect quasisovereign interests—i.e., public or governmental interests that concern 

the state as a whole.” Id., at 289; see, e.g., Missouri v. Illinois, 180 

U. S. 208, 240–241 (1901) (finding federal jurisdiction appropriate not

only “in cases involving boundaries and jurisdiction over lands and 

their inhabitants, and in cases directly affecting the property rights

and interests of a state,” but also when the “substantial impairment of

the health and prosperity of the towns and cities of the state” are at

stake).

 Drawing on Massachusetts v. Mellon, 262 U. S. 447 (1923), and Alfred 

L. Snapp & Son, Inc. v. Puerto Rico ex rel. Barez, 458 U. S. 592 (1982) 

(citing Missouri v. Illinois, 180 U. S. 208 (1901)), THE CHIEF JUSTICE 

claims that we “overloo[k] the fact that our cases cast significant doubt 

on a State’s standing to assert a quasi-sovereign interest . . . against

the Federal Government.” Post, at 5. Not so. Mellon itself disavowed 

any such broad reading when it noted that the Court had been “called 

upon to adjudicate, not rights of person or property, not rights of 

dominion over physical domain, [and] not quasi sovereign rights actually invaded or threatened.” 262 U. S., at 484–485 (emphasis added). 

In any event, we held in Georgia v. Pennsylvania R. Co., 324 U. S. 439, 

447 (1945), that there is a critical difference between allowing a State

“to protect her citizens from the operation of federal statutes” (which is

what Mellon prohibits) and allowing a State to assert its rights under

federal law (which it has standing to do). Massachusetts does not here 

dispute that the Clean Air Act applies to its citizens; it rather seeks to 

assert its rights under the Act. See also Nebraska v. Wyoming, 515 

U. S. 1, 20 (1995) (holding that Wyoming had standing to bring a crossclaim against the United States to vindicate its “ ‘quasi-sovereign’ 

interests which are ‘independent of and behind the titles of its citizens,

in all the earth and air within its domain’ ” (quoting Tennessee Copper, 

206 U. S., at 237)). 
18 MASSACHUSETTS v. EPA 

Opinion of the Court 

With that in mind, it is clear that petitioners’ submissions as they pertain to Massachusetts have satisfied the 

most demanding standards of the adversarial process. 

EPA’s steadfast refusal to regulate greenhouse gas emissions presents a risk of harm to Massachusetts that is

both “actual” and “imminent.” Lujan, 504 U. S., at 560 

(internal quotation marks omitted). There is, moreover, a 

“substantial likelihood that the judicial relief requested”

will prompt EPA to take steps to reduce that risk. Duke 

Power Co. v. Carolina Environmental Study Group, Inc., 

438 U. S. 59, 79 (1978). 

The Injury 

The harms associated with climate change are serious

and well recognized. Indeed, the NRC Report itself—

which EPA regards as an “objective and independent

assessment of the relevant science,” 68 Fed. Reg. 52930—

identifies a number of environmental changes that have

already inflicted significant harms, including “the global

retreat of mountain glaciers, reduction in snow-cover

extent, the earlier spring melting of rivers and lakes, [and]

the accelerated rate of rise of sea levels during the 20th 

century relative to the past few thousand years . . . .” 

NRC Report 16. 

Petitioners allege that this only hints at the environmental damage yet to come. According to the climate 

scientist Michael MacCracken, “qualified scientific experts

involved in climate change research” have reached a

“strong consensus” that global warming threatens (among 

other things) a precipitate rise in sea levels by the end of 

the century, MacCracken Decl. ¶15, Stdg. App. 207, “severe and irreversible changes to natural ecosystems,” id., 

¶5(d), at 209, a “significant reduction in water storage in

winter snowpack in mountainous regions with direct and

important economic consequences,” ibid., and an increase 

in the spread of disease, id., ¶28, at 218–219. He also 
Cite as: 549 U. S. ____ (2007) 19 

Opinion of the Court 

observes that rising ocean temperatures may contribute to 

the ferocity of hurricanes. Id., ¶¶23–25, at 216–217.18 

That these climate-change risks are “widely shared” 

does not minimize Massachusetts’ interest in the outcome 

of this litigation. See Federal Election Comm’n v. Akins, 

524 U. S. 11, 24 (1998) (“[W]here a harm is concrete, 

though widely shared, the Court has found ‘injury in

fact’”). According to petitioners’ unchallenged affidavits, 

global sea levels rose somewhere between 10 and 20 centimeters over the 20th century as a result of global warming. MacCracken Decl. ¶5(c), Stdg. App. 208. These rising 

seas have already begun to swallow Massachusetts’ 

coastal land. Id., at 196 (declaration of Paul H. Kirshen

¶5), 216 (MacCracken Decl. ¶23). Because the Commonwealth “owns a substantial portion of the state’s coastal 

property,” id., at 171 (declaration of Karst R. Hoogeboom 

¶4),19 it has alleged a particularized injury in its capacity 

—————— 

18 In this regard, MacCracken’s 2004 affidavit—drafted more than a 

year in advance of Hurricane Katrina—was eerily prescient. Immediately after discussing the “particular concern” that climate change 

might cause an “increase in the wind speed and peak rate of precipitation of major tropical cyclones (i.e., hurricanes and typhoons),” MacCracken noted that “[s]oil compaction, sea level rise and recurrent

storms are destroying approximately 20–30 square miles of Louisiana

wetlands each year. These wetlands serve as a ‘shock absorber’ for 

storm surges that could inundate New Orleans, significantly enhancing

the risk to a major urban population.” ¶¶24–25, Stdg. App. 217. 19 “For example, the [Massachusetts Department of Conservation and

Recreation] owns, operates and maintains approximately 53 coastal

state parks, beaches, reservations, and wildlife sanctuaries. [It] also

owns, operates and maintains sporting and recreational facilities in

coastal areas, including numerous pools, skating rinks, playgrounds,

playing fields, former coastal fortifications, public stages, museums,

bike trails, tennis courts, boathouses and boat ramps and landings. 

Associated with these coastal properties and facilities is a significant

amount of infrastructure, which the Commonwealth also owns, operates and maintains, including roads, parkways, stormwater pump 

stations, pier[s], sea wal[l] revetments and dams.” Hoogeboom Decl.

¶4, at 171. 
20 MASSACHUSETTS v. EPA 

Opinion of the Court 

as a landowner. The severity of that injury will only 

increase over the course of the next century: If sea levels

continue to rise as predicted, one Massachusetts official

believes that a significant fraction of coastal property will

be “either permanently lost through inundation or temporarily lost through periodic storm surge and flooding events.” 

Id., ¶6, at 172.20 Remediation costs alone, petitioners allege,

could run well into the hundreds of millions of dollars. Id., 

¶7, at 172; see also Kirshen Decl. ¶12, at 198.21 

Causation 

EPA does not dispute the existence of a causal connection between man-made greenhouse gas emissions and 

global warming. At a minimum, therefore, EPA’s refusal 

to regulate such emissions “contributes” to Massachusetts’ 

injuries.

EPA nevertheless maintains that its decision not to 

regulate greenhouse gas emissions from new motor vehicles contributes so insignificantly to petitioners’ injuries 

that the agency cannot be haled into federal court to answer for them. For the same reason, EPA does not believe 

—————— 

20See also id., at 179 (declaration of Christian Jacqz) (discussing

possible loss of roughly 14 acres of land per miles of coastline by 2100);

Kirshen Decl. ¶10, at 198 (alleging that “[w]hen such a rise in sea level

occurs, a 10-year flood will have the magnitude of the present 100-year

flood and a 100-year flood will have the magnitude of the present 500-

year flood”). 21 In dissent, THE CHIEF JUSTICE dismisses petitioners’ submissions as

“conclusory,” presumably because they do not quantify Massachusetts’ 

land loss with the exactitude he would prefer. Post, at 8. He therefore 

asserts that the Commonwealth’s injury is “conjectur[al].” See ibid. 

Yet the likelihood that Massachusetts’ coastline will recede has nothing 

to do with whether petitioners have determined the precise metes and 

bounds of their soon-to-be-flooded land. Petitioners maintain that the 

seas are rising and will continue to rise, and have alleged that such a 

rise will lead to the loss of Massachusetts’ sovereign territory. No one, 

save perhaps the dissenters, disputes those allegations. Our cases 

require nothing more. 
Cite as: 549 U. S. ____ (2007) 21 

Opinion of the Court 

that any realistic possibility exists that the relief petitioners seek would mitigate global climate change and remedy 

their injuries. That is especially so because predicted

increases in greenhouse gas emissions from developing 

nations, particularly China and India, are likely to offset 

any marginal domestic decrease. 

But EPA overstates its case. Its argument rests on the 

erroneous assumption that a small incremental step, 

because it is incremental, can never be attacked in a federal judicial forum. Yet accepting that premise would

doom most challenges to regulatory action. Agencies, like 

legislatures, do not generally resolve massive problems in

one fell regulatory swoop. See Williamson v. Lee Optical 

of Okla., Inc., 348 U. S. 483, 489 (1955) (“[A] reform may 

take one step at a time, addressing itself to the phase of

the problem which seems most acute to the legislative

mind”). They instead whittle away at them over time, 

refining their preferred approach as circumstances change

and as they develop a more-nuanced understanding of how 

best to proceed. Cf. SEC v. Chenery Corp., 332 U. S. 194, 

202 (1947) (“Some principles must await their own development, while others must be adjusted to meet particular, 

unforeseeable situations”). That a first step might be 

tentative does not by itself support the notion that federal 

courts lack jurisdiction to determine whether that step 

conforms to law. 

And reducing domestic automobile emissions is hardly a 

tentative step. Even leaving aside the other greenhouse 

gases, the United States transportation sector emits an 

enormous quantity of carbon dioxide into the atmosphere—according to the MacCracken affidavit, more than 

1.7 billion metric tons in 1999 alone. ¶30, Stdg. App. 219. 

That accounts for more than 6% of worldwide carbon 

dioxide emissions. Id., at 232 (Oppenheimer Decl. ¶3); see

also MacCracken Decl. ¶31, at 220. To put this in perspective: Considering just emissions from the transporta-
22 MASSACHUSETTS v. EPA 

Opinion of the Court 

tion sector, which represent less than one-third of this

country’s total carbon dioxide emissions, the United States

would still rank as the third-largest emitter of carbon

dioxide in the world, outpaced only by the European Union 

and China.22 Judged by any standard, U. S. motor-vehicle

emissions make a meaningful contribution to greenhouse

gas concentrations and hence, according to petitioners, to 

global warming. 

The Remedy 

While it may be true that regulating motor-vehicle 

emissions will not by itself reverse global warming, it by no

means follows that we lack jurisdiction to decide whether

EPA has a duty to take steps to slow or reduce it. See also 

Larson v. Valente, 456 U. S. 228, 244, n. 15 (1982) (“[A] 

plaintiff satisfies the redressability requirement when he 

shows that a favorable decision will relieve a discrete 

injury to himself. He need not show that a favorable 

decision will relieve his every injury”). Because of the 

enormity of the potential consequences associated with 

man-made climate change, the fact that the effectiveness

of a remedy might be delayed during the (relatively short) 

time it takes for a new motor-vehicle fleet to replace an

older one is essentially irrelevant.23 Nor is it dispositive 

—————— 

22See UNFCCC, National Greenhouse Gas Inventory Data for the Period 

1990–2004 and Status of Reporting 14 (2006) (hereinafter Inventory Data) 

(reflecting emissions from Annex I countries); UNFCCC, Sixth Compilation 

and Synthesis of Initial National Communications from Parties not Included in Annex I to the Convention 7–8 (2005) (reflecting emissions from 

non-Annex I countries); see also Dept. of Energy, Energy Information 

Admin., International Energy Annual 2004, H.1co2 World Carbon Dioxide

Emissions from the Consumption and Flaring of Fossil Fuels, 1980–2004

(Table), http://www.eia.doe.gov/pub/international/iealf/tableh1co2.xls. 23See also Mountain States Legal Foundation v. Glickman, 92 F. 3d 

1228, 1234 (CADC 1996) (“The more drastic the injury that government 

action makes more likely, the lesser the increment in probability to

establish standing”); Village of Elk Grove Village v. Evans, 997 F. 2d 

328, 329 (CA7 1993) (“[E]ven a small probability of injury is sufficient 
Cite as: 549 U. S. ____ (2007) 23 

Opinion of the Court 

that developing countries such as China and India are 

poised to increase greenhouse gas emissions substantially 

over the next century: A reduction in domestic emissions

would slow the pace of global emissions increases, no 

matter what happens elsewhere. 

We moreover attach considerable significance to EPA’s

“agree[ment] with the President that ‘we must address the 

issue of global climate change,’” 68 Fed. Reg. 52929 (quoting remarks announcing Clear Skies and Global Climate 

Initiatives, 2002 Public Papers of George W. Bush, Vol. 1, 

Feb. 14, p. 227 (2004)), and to EPA’s ardent support for 

various voluntary emission-reduction programs, 68 Fed. 

Reg. 52932. As Judge Tatel observed in dissent below, 

“EPA would presumably not bother with such efforts if it

thought emissions reductions would have no discernable 

impact on future global warming.” 415 F. 3d, at 66. 

In sum—at least according to petitioners’ uncontested

affidavits—the rise in sea levels associated with global 

warming has already harmed and will continue to harm

Massachusetts. The risk of catastrophic harm, though

remote, is nevertheless real. That risk would be reduced 

to some extent if petitioners received the relief they seek.

We therefore hold that petitioners have standing to challenge the EPA’s denial of their rulemaking petition.24 

—————— 

to create a case or controversy—to take a suit out of the category of the 

hypothetical—provided of course that the relief sought would, if 

granted, reduce the probability”). 24 In his dissent, THE CHIEF JUSTICE expresses disagreement with the 

Court’s holding in United States v. Students Challenging Regulatory 

Agency Procedures (SCRAP), 412 U. S. 669, 687–688 (1973). He does 

not, however, disavow this portion of Justice Stewart’s opinion for the 

Court: 

“Unlike the specific and geographically limited federal action of which 

the petitioner complained in Sierra Club [v. Morton, 405 U. S. 727 

(1972)], the challenged agency action in this case is applicable to

substantially all of the Nation’s railroads, and thus allegedly has an

adverse environmental impact on all the natural resources of the 
24 MASSACHUSETTS v. EPA 

Opinion of the Court

V 

The scope of our review of the merits of the statutory 

issues is narrow. As we have repeated time and again, an

agency has broad discretion to choose how best to marshal 

its limited resources and personnel to carry out its delegated responsibilities. See Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, 842–845 

(1984). That discretion is at its height when the agency 

decides not to bring an enforcement action. Therefore, in 

Heckler v. Chaney, 470 U. S. 821 (1985), we held that an

agency’s refusal to initiate enforcement proceedings is not 

ordinarily subject to judicial review. Some debate remains, however, as to the rigor with which we review an 

agency’s denial of a petition for rulemaking. 

There are key differences between a denial of a petition 

for rulemaking and an agency’s decision not to initiate an 

enforcement action. See American Horse Protection Assn., 

Inc. v. Lyng, 812 F. 2d 1, 3–4 (CADC 1987). In contrast to 

nonenforcement decisions, agency refusals to initiate

rulemaking “are less frequent, more apt to involve legal as 

opposed to factual analysis, and subject to special formali-

—————— 

country. Rather than a limited group of persons who used a picturesque valley in California, all persons who utilize the scenic resources

of the country, and indeed all who breathe its air, could claim harm 

similar to that alleged by the environmental groups here. But we have 

already made it clear that standing is not to be denied simply because 

many people suffer the same injury. Indeed some of the cases on which 

we relied in Sierra Club demonstrated the patent fact that persons

across the Nation could be adversely affected by major governmental 

actions. To deny standing to persons who are in fact injured simply 

because many others are also injured, would mean that the most injurious and widespread Government actions could be questioned by nobody. 

We cannot accept that conclusion.” Ibid. (citations omitted and emphasis added). 

It is moreover quite wrong to analogize the legal claim advanced by

Massachusetts and the other public and private entities who challenge 

EPA’s parsimonious construction of the Clean Air Act to a mere “lawyer’s game.” See post, at 14. 
Cite as: 549 U. S. ____ (2007) 25 

Opinion of the Court 

ties, including a public explanation.” Id., at 4; see also 5 

U. S. C. §555(e). They moreover arise out of denials of 

petitions for rulemaking which (at least in the circumstances here) the affected party had an undoubted procedural right to file in the first instance. Refusals to promulgate rules are thus susceptible to judicial review, though

such review is “extremely limited” and “highly deferential.” National Customs Brokers & Forwarders Assn of 

America, Inc. v. United States, 883 F. 2d 93, 96 (CADC 

1989).

EPA concluded in its denial of the petition for rulemaking that it lacked authority under 42 U. S. C. §7521(a)(1) 

to regulate new vehicle emissions because carbon dioxide 

is not an “air pollutant” as that term is defined in §7602. 

In the alternative, it concluded that even if it possessed

authority, it would decline to do so because regulation 

would conflict with other administration priorities. As 

discussed earlier, the Clean Air Act expressly permits 

review of such an action. §7607(b)(1). We therefore “may

reverse any such action found to be . . . arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.” §7607(d)(9). 

VI 

On the merits, the first question is whether §202(a)(1) of

the Clean Air Act authorizes EPA to regulate greenhouse 

gas emissions from new motor vehicles in the event that it 

forms a “judgment” that such emissions contribute to

climate change. We have little trouble concluding that it 

does. In relevant part, §202(a)(1) provides that EPA “shall

by regulation prescribe . . . standards applicable to the 

emission of any air pollutant from any class or classes of

new motor vehicles or new motor vehicle engines, which in 

[the Administrator’s] judgment cause, or contribute to, air

pollution which may reasonably be anticipated to endanger public health or welfare.” 42 U. S. C. §7521(a)(1). 
26 MASSACHUSETTS v. EPA 

Opinion of the Court 

Because EPA believes that Congress did not intend it to 

regulate substances that contribute to climate change, the

agency maintains that carbon dioxide is not an “air pollutant” within the meaning of the provision. 

The statutory text forecloses EPA’s reading. The Clean 

Air Act’s sweeping definition of “air pollutant” includes 

“any air pollution agent or combination of such agents, 

including any physical, chemical . . . substance or matter 

which is emitted into or otherwise enters the ambient 

air . . . .” §7602(g) (emphasis added). On its face, the 

definition embraces all airborne compounds of whatever

stripe, and underscores that intent through the repeated 

use of the word “any.”25 Carbon dioxide, methane, nitrous 

oxide, and hydrofluorocarbons are without a doubt “physical [and] chemical . . . substance[s] which [are] emitted

into . . . the ambient air.” The statute is unambiguous.26 

Rather than relying on statutory text, EPA invokes 

—————— 

25See Department of Housing and Urban Development v. Rucker, 535 

U. S. 125, 131 (2002) (observing that “‘any’ . . . has an expansive meaning, that is, one or some indiscriminately of whatever kind” (some internal quotation marks omitted)). 26 In dissent, JUSTICE SCALIA maintains that because greenhouse 

gases permeate the world’s atmosphere rather than a limited area near

the earth’s surface, EPA’s exclusion of greenhouse gases from the 

category of air pollution “agent[s]” is entitled to deference under Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc. 467 U. S. 

837 (1984). See post, at 11–13. EPA’s distinction, however, finds no 

support in the text of the statute, which uses the phrase “the ambient 

air” without distinguishing between atmospheric layers. Moreover, it is 

a plainly unreasonable reading of a sweeping statutory provision 

designed to capture “any physical, chemical . . . substance or matter

which is emitted into or otherwise enters the ambient air.” 42 U. S. C. 

§7602(g). JUSTICE SCALIA does not (and cannot) explain why Congress

would define “air pollutant” so carefully and so broadly, yet confer on

EPA the authority to narrow that definition whenever expedient by

asserting that a particular substance is not an “agent.” At any rate, no

party to this dispute contests that greenhouse gases both “ente[r] the 

ambient air” and tend to warm the atmosphere. They are therefore 

unquestionably “agent[s]” of air pollution. 
Cite as: 549 U. S. ____ (2007) 27 

Opinion of the Court 

postenactment congressional actions and deliberations it 

views as tantamount to a congressional command to refrain from regulating greenhouse gas emissions. Even if 

such postenactment legislative history could shed light on 

the meaning of an otherwise-unambiguous statute, EPA 

never identifies any action remotely suggesting that Congress meant to curtail its power to treat greenhouse gases 

as air pollutants. That subsequent Congresses have eschewed enacting binding emissions limitations to combat 

global warming tells us nothing about what Congress 

meant when it amended §202(a)(1) in 1970 and 1977.27 

And unlike EPA, we have no difficulty reconciling Congress’ various efforts to promote interagency collaboration 

and research to better understand climate change28 with 

the agency’s pre-existing mandate to regulate “any air 

pollutant” that may endanger the public welfare. See 42 

U. S. C. §7601(a)(1). Collaboration and research do not 

—————— 

27See United States v. Price, 361 U. S. 304, 313 (1960) (holding that 

“the views of a subsequent Congress form a hazardous basis for inferring the intent of an earlier one”); see also Cobell v. Norton, 428 F. 3d 

1070, 1075 (CADC 2005) (“[P]ost-enactment legislative history is not

only oxymoronic but inherently entitled to little weight”). 28See, e.g., National Climate Program Act, §5, 92 Stat. 601, 15 U. S. C. 

§2901 et seq. (calling for the establishment of a National Climate

Program and for additional climate change research); Global Climate 

Protection Act of 1987, §1103, 101 Stat. 1408–1409 (directing EPA and

the Secretary of State to “jointly” develop a “coordinated national policy 

on global climate change” and report to Congress); Global Change 

Research Act of 1990, Tit. I, 104 Stat. 3097, 15 U. S. C. §§2921–2938

(establishing for the “development and coordination of a comprehensive 

and integrated United States research program” to aid in “understand[ing] . . . human-induced and natural processes of climate 

change”); Global Climate Change Prevention Act of 1990, 104 Stat.

4058, 7 U. S. C. §6701 et seq. (directing the Dept. of Agriculture to

study the effects of climate change on forestry and agriculture); Energy

Policy Act of 1992, §§1601–1609, 106 Stat. 2999, 42 U. S. C. §§13381–

13388 (requiring the Secretary of Energy to report on information 

pertaining to climate change). 
28 MASSACHUSETTS v. EPA 

Opinion of the Court 

conflict with any thoughtful regulatory effort; they complement it.29

 EPA’s reliance on Brown & Williamson Tobacco Corp., 

529 U. S. 120, is similarly misplaced. In holding that 

tobacco products are not “drugs” or “devices” subject to

Food and Drug Administration (FDA) regulation pursuant 

to the Food, Drug and Cosmetic Act (FDCA), see 529 U. S., 

at 133, we found critical at least two considerations that 

have no counterpart in this case. 

First, we thought it unlikely that Congress meant to ban

tobacco products, which the FDCA would have required

had such products been classified as “drugs” or “devices.” 

Id., at 135–137. Here, in contrast, EPA jurisdiction would 

lead to no such extreme measures. EPA would only regulate emissions, and even then, it would have to delay any 

action “to permit the development and application of the 

requisite technology, giving appropriate consideration to 

the cost of compliance,” §7521(a)(2). However much a ban 

on tobacco products clashed with the “common sense” 

intuition that Congress never meant to remove those 

products from circulation, Brown & Williamson, 529 U. S., 

at 133, there is nothing counterintuitive to the notion that

EPA can curtail the emission of substances that are putting the global climate out of kilter. 

 Second, in Brown & Williamson we pointed to an unbroken series of congressional enactments that made sense 

only if adopted “against the backdrop of the FDA’s consistent and repeated statements that it lacked authority under 

the FDCA to regulate tobacco.” Id., at 144. We can point to 

no such enactments here: EPA has not identified any congressional action that conflicts in any way with the regula-

—————— 

29We are moreover puzzled by EPA’s roundabout argument that because later Congresses chose to address stratospheric ozone pollution in 

a specific legislative provision, it somehow follows that greenhouse 

gases cannot be air pollutants within the meaning of the Clean Air Act. 
Cite as: 549 U. S. ____ (2007) 29 

Opinion of the Court 

tion of greenhouse gases from new motor vehicles. Even if 

it had, Congress could not have acted against a regulatory 

“backdrop” of disclaimers of regulatory authority. Prior to 

the order that provoked this litigation, EPA had never 

disavowed the authority to regulate greenhouse gases, and

in 1998 it in fact affirmed that it had such authority. See 

App. 54 (Cannon memorandum). There is no reason, much 

less a compelling reason, to accept EPA’s invitation to read

ambiguity into a clear statute. 

EPA finally argues that it cannot regulate carbon dioxide emissions from motor vehicles because doing so would 

require it to tighten mileage standards, a job (according to 

EPA) that Congress has assigned to DOT. See 68 Fed. 

Reg. 52929. But that DOT sets mileage standards in no

way licenses EPA to shirk its environmental responsibilities. EPA has been charged with protecting the public’s

“health” and “welfare,” 42 U. S. C. §7521(a)(1), a statutory 

obligation wholly independent of DOT’s mandate to promote energy efficiency. See Energy Policy and Conservation Act, §2(5), 89 Stat. 874, 42 U. S. C. §6201(5). The two 

obligations may overlap, but there is no reason to think 

the two agencies cannot both administer their obligations

and yet avoid inconsistency. 

While the Congresses that drafted §202(a)(1) 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. The broad language of §202(a)(1) reflects an 

intentional effort to confer the flexibility necessary to 

forestall such obsolescence. See Pennsylvania Dept. of 

Corrections v. Yeskey, 524 U. S. 206, 212 (1998) (“[T]he

fact that a statute can be applied in situations not expressly anticipated by Congress does not demonstrate

ambiguity. It demonstrates breadth” (internal quotation 

marks omitted)). Because greenhouse gases fit well within 
30 MASSACHUSETTS v. EPA 

Opinion of the Court 

the Clean Air Act’s capacious definition of “air pollutant,”

we hold that EPA has the statutory authority to regulate

the emission of such gases from new motor vehicles. 

VII 

The alternative basis for EPA’s decision—that even if it 

does have statutory authority to regulate greenhouse

gases, it would be unwise to do so at this time—rests on 

reasoning divorced from the statutory text. While the 

statute does condition the exercise of EPA’s authority on

its formation of a “judgment,” 42 U. S. C. §7521(a)(1), that 

judgment must relate to whether an air pollutant

“cause[s], or contribute[s] to, air pollution which may

reasonably be anticipated to endanger public health or 

welfare,” ibid. Put another way, the use of the word “judgment” is not a roving license to ignore the statutory text.

It is but a direction to exercise discretion within defined 

statutory limits. 

If EPA makes a finding of endangerment, the Clean Air 

Act requires the agency to regulate emissions of the deleterious pollutant from new motor vehicles. Ibid. (stating

that “[EPA] shall by regulation prescribe . . . standards

applicable to the emission of any air pollutant from any 

class of new motor vehicles”). EPA no doubt has significant latitude as to the manner, timing, content, and coordination of its regulations with those of other agencies.

But once EPA has responded to a petition for rulemaking,

its reasons for action or inaction must conform to the 

authorizing statute. Under the clear terms of the Clean 

Air Act, EPA can avoid taking further action only if it

determines that greenhouse gases do not contribute to

climate change or if it provides some reasonable explanation as to why it cannot or will not exercise its discretion

to determine whether they do. Ibid. To the extent that 

this constrains agency discretion to pursue other priorities 

of the Administrator or the President, this is the congressional design. 
Cite as: 549 U. S. ____ (2007) 31 

Opinion of the Court 

EPA has refused to comply with this clear statutory

command. Instead, it has offered a laundry list of reasons

not to regulate. For example, EPA said that a number of 

voluntary executive branch programs already provide an 

effective response to the threat of global warming, 68 Fed. 

Reg. 52932, that regulating greenhouse gases might impair the President’s ability to negotiate with “key developing nations” to reduce emissions, id., at 52931, and that 

curtailing motor-vehicle emissions would reflect “an inefficient, piecemeal approach to address the climate change 

issue,” ibid. 

Although we have neither the expertise nor the authority to evaluate these policy judgments, it is evident they

have nothing to do with whether greenhouse gas emissions contribute to climate change. Still less do they

amount to a reasoned justification for declining to form a

scientific judgment. In particular, while the President has

broad authority in foreign affairs, that authority does not 

extend to the refusal to execute domestic laws. In the 

Global Climate Protection Act of 1987, Congress authorized the State Department—not EPA—to formulate United

States foreign policy with reference to environmental matters relating to climate. See §1103(c), 101 Stat. 1409. EPA 

has made no showing that it issued the ruling in question

here after consultation with the State Department. Congress did direct EPA to consult with other agencies in the

formulation of its policies and rules, but the State Department is absent from that list. §1103(b). 

Nor can EPA avoid its statutory obligation by noting the

uncertainty surrounding various features of climate change

and concluding that it would therefore be better not to

regulate at this time. See 68 Fed. Reg. 52930–52931. If the 

scientific uncertainty is so profound that it precludes EPA 

from making a reasoned judgment as to whether greenhouse gases contribute to global warming, EPA must say 

so. That EPA would prefer not to regulate greenhouse 
32 MASSACHUSETTS v. EPA 

Opinion of the Court 

gases because of some residual uncertainty—which, contrary to JUSTICE SCALIA’s apparent belief, post, at 5–8, is 

in fact all that it said, see 68 Fed. Reg. 52929 (“We do not 

believe . . . that it would be either effective or appropriate

for EPA to establish [greenhouse gas] standards for motor 

vehicles at this time” (emphasis added))—is irrelevant. 

The statutory question is whether sufficient information 

exists to make an endangerment finding.

In short, EPA has offered no reasoned explanation for 

its refusal to decide whether greenhouse gases cause or

contribute to climate change. Its action was therefore 

“arbitrary, capricious, . . . or otherwise not in accordance 

with law.” 42 U. S. C. §7607(d)(9)(A). We need not and do 

not reach the question whether on remand EPA must 

make an endangerment finding, or whether policy concerns can inform EPA’s actions in the event that it makes 

such a finding. Cf. Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, 843–844 

(1984). We hold only that EPA must ground its reasons 

for action or inaction in the statute. 

VIII 

The judgment of the Court of Appeals is reversed, and

the case is remanded for further proceedings consistent

with this opinion. 

It is so ordered. 
_________________ 

_________________ 

Cite as: 549 U. S. ____ (2007) 1 

ROBERTS, C. J., dissenting 

SUPREME COURT OF THE UNITED STATES 

No. 05–1120 

MASSACHUSETTS, ET AL., PETITIONERS v. ENVIRONMENTAL PROTECTION AGENCY ET AL. 

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF

APPEALS FOR THE DISTRICT OF COLUMBIA CIRCUIT

[April 2, 2007]

 CHIEF JUSTICE ROBERTS, with whom JUSTICE SCALIA, 

JUSTICE THOMAS, and JUSTICE ALITO join, dissenting. 

Global warming may be a “crisis,” even “the most pressing environmental problem of our time.” Pet. for Cert. 26, 

22. Indeed, it may ultimately affect nearly everyone on 

the planet in some potentially adverse way, and it may be

that governments have done too little to address it. It is 

not a problem, however, that has escaped the attention of

policymakers in the Executive and Legislative Branches of 

our Government, who continue to consider regulatory, 

legislative, and treaty-based means of addressing global

climate change.

Apparently dissatisfied with the pace of progress on this 

issue in the elected branches, petitioners have come to the 

courts claiming broad-ranging injury, and attempting to

tie that injury to the Government’s alleged failure to 

comply with a rather narrow statutory provision. I would 

reject these challenges as nonjusticiable. Such a conclusion involves no judgment on whether global warming 

exists, what causes it, or the extent of the problem. Nor 

does it render petitioners without recourse. This Court’s 

standing jurisprudence simply recognizes that redress of

grievances of the sort at issue here “is the function of 

Congress and the Chief Executive,” not the federal courts. 

Lujan v. Defenders of Wildlife, 504 U. S. 555, 576 (1992). I 
2 MASSACHUSETTS v. EPA 

ROBERTS, C. J., dissenting 

would vacate the judgment below and remand for dismissal of the petitions for review. 

I 

Article III, §2, of the Constitution limits the federal 

judicial power to the adjudication of “Cases” and “Controversies.” “If a dispute is not a proper case or controversy,

the courts have no business deciding it, or expounding the

law in the course of doing so.” DaimlerChrysler Corp. v. 

Cuno, 547 U. S. ___, ___ (2006) (slip op., at 5). “Standing

to sue is part of the common understanding of what it 

takes to make a justiciable case,” Steel Co. v. Citizens for 

Better Environment, 523 U. S. 83, 102 (1998), and has

been described as “an essential and unchanging part of the 

case-or-controversy requirement of Article III,” Defenders 

of Wildlife, supra, at 560. 

Our modern framework for addressing standing is familiar: “A plaintiff must allege personal injury fairly traceable to the defendant’s allegedly unlawful conduct and 

likely to be redressed by the requested relief.” DaimlerChrysler, supra, at ___ (slip op., at 6) (quoting Allen v. 

Wright, 468 U. S. 737, 751 (1984) (internal quotation

marks omitted)). Applying that standard here, petitioners

bear the burden of alleging an injury that is fairly traceable to the Environmental Protection Agency’s failure to 

promulgate new motor vehicle greenhouse gas emission

standards, and that is likely to be redressed by the prospective issuance of such standards. 

Before determining whether petitioners can meet this 

familiar test, however, the Court changes the rules. It 

asserts that “States are not normal litigants for the purposes of invoking federal jurisdiction,” and that given

“Massachusetts’ stake in protecting its quasi-sovereign

interests, the Commonwealth is entitled to special solicitude in our standing analysis.” Ante, at 15, 17 (emphasis 

added). 
Cite as: 549 U. S. ____ (2007) 3 

ROBERTS, C. J., dissenting 

Relaxing Article III standing requirements because

asserted injuries are pressed by a State, however, has no

basis in our jurisprudence, and support for any such “special solicitude” is conspicuously absent from the Court’s

opinion. The general judicial review provision cited by the 

Court, 42 U. S. C. §7607(b)(1), affords States no special 

rights or status. The Court states that “Congress has 

ordered EPA to protect Massachusetts (among others)”

through the statutory provision at issue, §7521(a)(1), and 

that “Congress has . . . recognized a concomitant procedural right to challenge the rejection of its rulemaking

petition as arbitrary and capricious.” Ante, at 16. The 

reader might think from this unfortunate phrasing that

Congress said something about the rights of States in this 

particular provision of the statute. Congress knows how 

to do that when it wants to, see, e.g., §7426(b) (affording 

States the right to petition EPA to directly regulate certain sources of pollution), but it has done nothing of the 

sort here. Under the law on which petitioners rely, Congress treated public and private litigants exactly the same. 

Nor does the case law cited by the Court provide any

support for the notion that Article III somehow implicitly

treats public and private litigants differently. The Court 

has to go back a full century in an attempt to justify its

novel standing rule, but even there it comes up short. The 

Court’s analysis hinges on Georgia v. Tennessee Copper 

Co., 206 U. S. 230 (1907)—a case that did indeed draw a

distinction between a State and private litigants, but 

solely with respect to available remedies. The case had 

nothing to do with Article III standing. 

In Tennessee Copper, the State of Georgia sought to 

enjoin copper companies in neighboring Tennessee from

discharging pollutants that were inflicting “a wholesale 

destruction of forests, orchards and crops” in bordering

Georgia counties. Id., at 236. Although the State owned 

very little of the territory allegedly affected, the Court 
4 MASSACHUSETTS v. EPA 

ROBERTS, C. J., dissenting 

reasoned that Georgia—in its capacity as a “quasisovereign”—“has an interest independent of and behind 

the titles of its citizens, in all the earth and air within its 

domain.” Id., at 237. The Court explained that while 

“[t]he very elements that would be relied upon in a suit 

between fellow-citizens as a ground for equitable relief

[were] wanting,” a State “is not lightly to be required to

give up quasi-sovereign rights for pay.” Ibid. Thus while 

a complaining private litigant would have to make do with 

a legal remedy—one “for pay”—the State was entitled to 

equitable relief. See id., at 237–238. 

In contrast to the present case, there was no question in 

Tennessee Copper about Article III injury. See id., at 238– 

239. There was certainly no suggestion that the State 

could show standing where the private parties could not; 

there was no dispute, after all, that the private landowners had “an action at law.” Id., at 238. Tennessee Copper

has since stood for nothing more than a State’s right, in an

original jurisdiction action, to sue in a representative

capacity as parens patriae. See, e.g., Maryland v. Louisiana, 451 U. S. 725, 737 (1981). Nothing about a State’s

ability to sue in that capacity dilutes the bedrock requirement of showing injury, causation, and redressability to 

satisfy Article III.

A claim of parens patriae standing is distinct from an 

allegation of direct injury. See Wyoming v. Oklahoma, 502 

U. S. 437, 448–449, 451 (1992). Far from being a substitute for Article III injury, parens patriae actions raise an 

additional hurdle for a state litigant: the articulation of a

“quasi-sovereign interest” “apart from the interests of 

particular private parties.” Alfred L. Snapp & Son, Inc. v. 

Puerto Rico ex rel. Barez, 458 U. S. 592, 607 (1982) (emphasis added) (cited ante, at 16). Just as an association 

suing on behalf of its members must show not only that it 

represents the members but that at least one satisfies 

Article III requirements, so too a State asserting quasi-
Cite as: 549 U. S. ____ (2007) 5 

ROBERTS, C. J., dissenting 

sovereign interests as parens patriae must still show that 

its citizens satisfy Article III. Focusing on Massachusetts’s interests as quasi-sovereign makes the required

showing here harder, not easier. The Court, in effect, 

takes what has always been regarded as a necessary condition for parens patriae standing—a quasi-sovereign interest—and converts it into a sufficient showing for purposes 

of Article III. 

What is more, the Court’s reasoning falters on its own 

terms. The Court asserts that Massachusetts is entitled 

to “special solicitude” due to its “quasi-sovereign interests,” ante, at 17, but then applies our Article III standing 

test to the asserted injury of the State’s loss of coastal 

property. See ante, at 19 (concluding that Massachusetts

“has alleged a particularized injury in its capacity as a 

landowner” (emphasis added)). In the context of parens 

patriae standing, however, we have characterized state 

ownership of land as a “nonsovereign interes[t]” because a

State “is likely to have the same interests as other similarly situated proprietors.” Alfred L. Snapp & Son, supra, 

at 601. 

On top of everything else, the Court overlooks the fact 

that our cases cast significant doubt on a State’s standing 

to assert a quasi-sovereign interest—as opposed to a direct 

injury—against the Federal Government. As a general

rule, we have held that while a State might assert a quasisovereign right as parens patriae “for the protection of its

citizens, it is no part of its duty or power to enforce their

rights in respect of their relations with the Federal Government. In that field it is the United States, and not the 

State, which represents them.” Massachusetts v. Mellon, 

262 U. S. 447, 485–486 (1923) (citation omitted); see also 

Alfred L. Snapp & Son, supra, at 610, n. 16. 

All of this presumably explains why petitioners never 

cited Tennessee Copper in their briefs before this Court or 

the D. C. Circuit. It presumably explains why not one of 
6 MASSACHUSETTS v. EPA 

ROBERTS, C. J., dissenting 

the legion of amici supporting petitioners ever cited the 

case. And it presumably explains why not one of the three

judges writing below ever cited the case either. Given that 

one purpose of the standing requirement is “‘to assure 

that concrete adverseness which sharpens the presentation of issues upon which the court so largely depends for

illumination,’” ante, at 13–14 (quoting Baker v. Carr, 369 

U. S. 186, 204 (1962)), it is ironic that the Court today 

adopts a new theory of Article III standing for States 

without the benefit of briefing or argument on the point.1 

II 

It is not at all clear how the Court’s “special solicitude” 

for Massachusetts plays out in the standing analysis,

except as an implicit concession that petitioners cannot 

establish standing on traditional terms. But the status of 

Massachusetts as a State cannot compensate for petitioners’ failure to demonstrate injury in fact, causation, and 

redressability.

When the Court actually applies the three-part test, it

focuses, as did the dissent below, see 415 F. 3d 50, 64 

—————— 

1The Court seems to think we do not recognize that Tennessee Copper 

is a case about parens patriae standing, ante, at 17, n. 17, but we have 

no doubt about that. The point is that nothing in our cases (or Hart &

Wechsler) suggests that the prudential requirements for parens patriae 

standing, see Republic of Venezuela v. Philip Morris Inc., 287 F. 3d 192, 

199, n. (CADC 2002) (observing that “parens patriae is merely a species 

of prudential standing” (internal quotation marks omitted)), can

somehow substitute for, or alter the content of, the “irreducible constitutional minimum” requirements of injury in fact, causation, and 

redressability under Article III. Lujan v. Defenders of Wildlife, 504 

U. S. 555, 560 (1992). 

 Georgia v. Pennsylvania R. Co., 324 U. S. 439 (1945), is not to the 

contrary. As the caption makes clear enough, the fact that a State may

assert rights under a federal statute as parens patriae in no way refutes

our clear ruling that “[a] State does not have standing as parens patriae 

to bring an action against the Federal Government.” Alfred L. Snapp & 

Son, Inc. v. Puerto Rico ex rel. Barez, 458 U. S. 592, 610, n. 16 (1982). 
Cite as: 549 U. S. ____ (2007) 7 

ROBERTS, C. J., dissenting 

(CADC 2005) (opinion of Tatel, J.), on the State’s asserted 

loss of coastal land as the injury in fact. If petitioners rely

on loss of land as the Article III injury, however, they

must ground the rest of the standing analysis in that 

specific injury. That alleged injury must be “concrete and 

particularized,” Defenders of Wildlife, 504 U. S., at 560, 

and “distinct and palpable,” Allen, 468 U. S., at 751 (internal quotation marks omitted). Central to this concept

of “particularized” injury is the requirement that a plaintiff be affected in a “personal and individual way,” Defenders of Wildlife, 504 U. S., at 560, n. 1, and seek relief that 

“directly and tangibly benefits him” in a manner distinct 

from its impact on “the public at large,” id., at 573–574. 

Without “particularized injury, there can be no confidence 

of ‘a real need to exercise the power of judicial review’ or 

that relief can be framed ‘no broader than required by the

precise facts to which the court’s ruling would be applied.’” 

Warth v. Seldin, 422 U. S. 490, 508 (1975) (quoting 

Schlesinger v. Reservists Comm. to Stop the War, 418 U. S. 

208, 221–222 (1974)). 

The very concept of global warming seems inconsistent 

with this particularization requirement. Global warming

is a phenomenon “harmful to humanity at large,” 415

F. 3d, at 60 (Sentelle, J., dissenting in part and concurring

in judgment), and the redress petitioners seek is focused

no more on them than on the public generally—it is literally to change the atmosphere around the world.

If petitioners’ particularized injury is loss of coastal 

land, it is also that injury that must be “actual or imminent, not conjectural or hypothetical,” Defenders of Wildlife, supra, at 560 (internal quotation marks omitted), 

“real and immediate,” Los Angeles v. Lyons, 461 U. S. 95, 

102 (1983) (internal quotation marks omitted), and “certainly impending,” Whitmore v. Arkansas, 495 U. S. 149, 

158 (1990) (internal quotation marks omitted).

As to “actual” injury, the Court observes that “global sea 
8 MASSACHUSETTS v. EPA 

ROBERTS, C. J., dissenting 

levels rose somewhere between 10 and 20 centimeters over 

the 20th century as a result of global warming” and that 

“[t]hese rising seas have already begun to swallow Massachusetts’ coastal land.” Ante, at 19. But none of petitioners’ declarations supports that connection. One declaration states that “a rise in sea level due to climate change is 

occurring on the coast of Massachusetts, in the metropolitan Boston area,” but there is no elaboration. Petitioners’ 

Standing Appendix in No. 03–1361, etc. (CADC), p. 196 

(Stdg. App.). And the declarant goes on to identify a “significan[t]” non-global-warming cause of Boston’s rising sea 

level: land subsidence. Id., at 197; see also id., at 216. 

Thus, aside from a single conclusory statement, there is 

nothing in petitioners’ 43 standing declarations and accompanying exhibits to support an inference of actual loss 

of Massachusetts coastal land from 20th century global 

sea level increases. It is pure conjecture. 

The Court’s attempts to identify “imminent” or “certainly impending” loss of Massachusetts coastal land fares 

no better. See ante, at 19–20. One of petitioners’ declarants predicts global warming will cause sea level to rise 

by 20 to 70 centimeters by the year 2100. Stdg. App. 216.

Another uses a computer modeling program to map the 

Commonwealth’s coastal land and its current elevation, 

and calculates that the high-end estimate of sea level rise 

would result in the loss of significant state-owned coastal

land. Id., at 179. But the computer modeling program 

has a conceded average error of about 30 centimeters and 

a maximum observed error of 70 centimeters. Id., at 177– 

178. As an initial matter, if it is possible that the model

underrepresents the elevation of coastal land to an extent 

equal to or in excess of the projected sea level rise, it is

difficult to put much stock in the predicted loss of land.

But even placing that problem to the side, accepting a 

century-long time horizon and a series of compounded 

estimates renders requirements of imminence and imme-
Cite as: 549 U. S. ____ (2007) 9 

ROBERTS, C. J., dissenting 

diacy utterly toothless. See Defenders of Wildlife, supra, 

at 565, n. 2 (while the concept of “‘imminence’” in standing doctrine is “somewhat elastic,” it can be “stretched

beyond the breaking point”). “Allegations of possible 

future injury do not satisfy the requirements of Art. III. A 

threatened injury must be certainly impending to constitute injury in fact.” Whitmore, supra, at 158. (internal 

quotation marks omitted; emphasis added). 

III 

Petitioners’ reliance on Massachusetts’s loss of coastal 

land as their injury in fact for standing purposes creates 

insurmountable problems for them with respect to causation and redressability. To establish standing, petitioners

must show a causal connection between that specific

injury and the lack of new motor vehicle greenhouse gas

emission standards, and that the promulgation of such 

standards would likely redress that injury. As is often the 

case, the questions of causation and redressability overlap. 

See Allen, 468 U. S., at 753, n. 19 (observing that the two 

requirements were “initially articulated by this Court as

two facets of a single causation requirement” (internal 

quotation marks omitted)). And importantly, when a 

party is challenging the Government’s allegedly unlawful

regulation, or lack of regulation, of a third party, satisfying the causation and redressability requirements becomes “substantially more difficult.” Defenders of Wildlife, 

supra, at 562 (internal quotation marks omitted); see also 

Warth, supra, at 504–505. 

Petitioners view the relationship between their injuries

and EPA’s failure to promulgate new motor vehicle greenhouse gas emission standards as simple and direct: Domestic motor vehicles emit carbon dioxide and other 

greenhouse gases. Worldwide emissions of greenhouse 

gases contribute to global warming and therefore also to 

petitioners’ alleged injuries. Without the new vehicle 
10 MASSACHUSETTS v. EPA 

ROBERTS, C. J., dissenting 

standards, greenhouse gas emissions—and therefore 

global warming and its attendant harms—have been 

higher than they otherwise would have been; once EPA 

changes course, the trend will be reversed.

The Court ignores the complexities of global warming,

and does so by now disregarding the “particularized”

injury it relied on in step one, and using the dire nature of

global warming itself as a bootstrap for finding causation

and redressability. First, it is important to recognize the

extent of the emissions at issue here. Because local 

greenhouse gas emissions disperse throughout the atmosphere and remain there for anywhere from 50 to 200

years, it is global emissions data that are relevant. See 

App. to Pet. for Cert. A–73. According to one of petitioners’ declarations, domestic motor vehicles contribute about 

6 percent of global carbon dioxide emissions and 4 percent 

of global greenhouse gas emissions. Stdg. App. 232. The 

amount of global emissions at issue here is smaller still; 

§202(a)(1) of the Clean Air Act covers only new motor 

vehicles and new motor vehicle engines, so petitioners’ 

desired emission standards might reduce only a fraction of 

4 percent of global emissions. 

This gets us only to the relevant greenhouse gas emissions; linking them to global warming and ultimately to 

petitioners’ alleged injuries next requires consideration of 

further complexities. As EPA explained in its denial of 

petitioners’ request for rulemaking, 

“predicting future climate change necessarily involves 

a complex web of economic and physical factors including: our ability to predict future global anthropogenic emissions of [greenhouse gases] and aerosols;

the fate of these emissions once they enter the atmosphere (e.g., what percentage are absorbed by vegetation or are taken up by the oceans); the impact of

those emissions that remain in the atmosphere on the 
Cite as: 549 U. S. ____ (2007) 11 

ROBERTS, C. J., dissenting 

radiative properties of the atmosphere; changes in 

critically important climate feedbacks (e.g., changes in

cloud cover and ocean circulation); changes in temperature characteristics (e.g., average temperatures, 

shifts in daytime and evening temperatures); changes

in other climatic parameters (e.g., shifts in precipitation, storms); and ultimately the impact of such 

changes on human health and welfare (e.g., increases 

or decreases in agricultural productivity, human 

health impacts).” App. to Pet. for Cert. A–83 through 

A–84. 

Petitioners are never able to trace their alleged injuries 

back through this complex web to the fractional amount of 

global emissions that might have been limited with EPA 

standards. In light of the bit-part domestic new motor 

vehicle greenhouse gas emissions have played in what

petitioners describe as a 150-year global phenomenon, and 

the myriad additional factors bearing on petitioners’ alleged injury—the loss of Massachusetts coastal land—the

connection is far too speculative to establish causation. 

IV 

Redressability is even more problematic. To the tenuous link between petitioners’ alleged injury and the indeterminate fractional domestic emissions at issue here, add 

the fact that petitioners cannot meaningfully predict what

will come of the 80 percent of global greenhouse gas emissions that originate outside the United States. As the 

Court acknowledges, “developing countries such as China 

and India are poised to increase greenhouse gas emissions 

substantially over the next century,” ante, at 23, so the 

domestic emissions at issue here may become an increasingly marginal portion of global emissions, and any decreases produced by petitioners’ desired standards are 

likely to be overwhelmed many times over by emissions

increases elsewhere in the world. 
12 MASSACHUSETTS v. EPA 

ROBERTS, C. J., dissenting 

Petitioners offer declarations attempting to address this

uncertainty, contending that “[i]f the U. S. takes steps to

reduce motor vehicle emissions, other countries are very

likely to take similar actions regarding their own motor 

vehicles using technology developed in response to the 

U. S. program.” Stdg. App. 220; see also id., at 311–312. 

In other words, do not worry that other countries will 

contribute far more to global warming than will U. S. 

automobile emissions; someone is bound to invent something, and places like the People’s Republic of China or

India will surely require use of the new technology, regardless of cost. The Court previously has explained that 

when the existence of an element of standing “depends on 

the unfettered choices made by independent actors not

before the courts and whose exercise of broad and legitimate discretion the courts cannot presume either to control or to predict,” a party must present facts supporting

an assertion that the actor will proceed in such a manner. 

Defenders of Wildlife, 504 U. S., at 562 (quoting ASARCO 

Inc. v. Kadish, 490 U. S. 605, 615 (1989) (opinion of 

KENNEDY, J.); internal quotation marks omitted). The 

declarations’ conclusory (not to say fanciful) statements do

not even come close. 

No matter, the Court reasons, because any decrease in 

domestic emissions will “slow the pace of global emissions

increases, no matter what happens elsewhere.” Ante, at 

23. Every little bit helps, so Massachusetts can sue over 

any little bit.

The Court’s sleight-of-hand is in failing to link up the

different elements of the three-part standing test. What 

must be likely to be redressed is the particular injury in 

fact. The injury the Court looks to is the asserted loss of 

land. The Court contends that regulating domestic motor

vehicle emissions will reduce carbon dioxide in the atmosphere, and therefore redress Massachusetts’s injury. But 

even if regulation does reduce emissions—to some inde-
Cite as: 549 U. S. ____ (2007) 13 

ROBERTS, C. J., dissenting 

terminate degree, given events elsewhere in the world—

the Court never explains why that makes it likely that the 

injury in fact—the loss of land—will be redressed. Schoolchildren know that a kingdom might be lost “all for the 

want of a horseshoe nail,” but “likely” redressability is a

different matter. The realities make it pure conjecture to

suppose that EPA regulation of new automobile emissions 

will likely prevent the loss of Massachusetts coastal land. 

V 

Petitioners’ difficulty in demonstrating causation and 

redressability is not surprising given the evident mismatch between the source of their alleged injury—

catastrophic global warming—and the narrow subject

matter of the Clean Air Act provision at issue in this suit.

The mismatch suggests that petitioners’ true goal for this 

litigation may be more symbolic than anything else. The 

constitutional role of the courts, however, is to decide 

concrete cases—not to serve as a convenient forum for 

policy debates. See Valley Forge Christian College v. 

Americans United for Separation of Church and State, 

Inc., 454 U. S. 464, 472 (1982) (“[Standing] tends to assure 

that the legal questions presented to the court will be 

resolved, not in the rarified atmosphere of a debating 

society, but in a concrete factual context conducive to

a realistic appreciation of the consequences of judicial

action”).

When dealing with legal doctrine phrased in terms of

what is “fairly” traceable or “likely” to be redressed, it is 

perhaps not surprising that the matter is subject to some 

debate. But in considering how loosely or rigorously to

define those adverbs, it is vital to keep in mind the purpose of the inquiry. The limitation of the judicial power to 

cases and controversies “is crucial in maintaining the 

tripartite allocation of power set forth in the Constitution.” 

DaimlerChrysler, 547 U. S., at ___ (slip op., at 5) (internal 
14 MASSACHUSETTS v. EPA 

ROBERTS, C. J., dissenting 

quotation marks omitted). In my view, the Court today—

addressing Article III’s “core component of standing,” 

Defenders of Wildlife, supra, at 560—fails to take this 

limitation seriously. 

To be fair, it is not the first time the Court has done so. 

Today’s decision recalls the previous high-water mark of 

diluted standing requirements, United States v. Students 

Challenging Regulatory Agency Procedures (SCRAP), 412 

U. S. 669 (1973). SCRAP involved “[p]robably the most 

attenuated injury conferring Art. III standing” and “surely 

went to the very outer limit of the law”—until today. 

Whitmore, 495 U. S., at 158–159; see also Lujan v. National Wildlife Federation, 497 U. S. 871, 889 (1990) 

(SCRAP “has never since been emulated by this Court”). 

In SCRAP, the Court based an environmental group’s

standing to challenge a railroad freight rate surcharge on

the group’s allegation that increases in railroad rates 

would cause an increase in the use of nonrecyclable goods, 

resulting in the increased need for natural resources to 

produce such goods. According to the group, some of these

resources might be taken from the Washington area,

resulting in increased refuse that might find its way into

area parks, harming the group’s members. 412 U. S., at 

688. 

 Over time, SCRAP became emblematic not of the looseness of Article III standing requirements, but of how 

utterly manipulable they are if not taken seriously as a 

matter of judicial self-restraint. SCRAP made standing 

seem a lawyer’s game, rather than a fundamental limitation ensuring that courts function as courts and not intrude on the politically accountable branches. Today’s

decision is SCRAP for a new generation.2 

—————— 

2The difficulty with SCRAP, and the reason it has not been followed, 

is not the portion cited by the Court. See ante, at 23–24, n. 24. Rather, 

it is the attenuated nature of the injury there, and here, that is so 
Cite as: 549 U. S. ____ (2007) 15 

ROBERTS, C. J., dissenting 

Perhaps the Court recognizes as much. How else to 

explain its need to devise a new doctrine of state standing

to support its result? The good news is that the Court’s

“special solicitude” for Massachusetts limits the future 

applicability of the diluted standing requirements applied 

in this case. The bad news is that the Court’s selfprofessed relaxation of those Article III requirements has 

caused us to transgress “the proper—and properly limited—role of the courts in a democratic society.” Allen, 468 

U. S., at 750 (internal quotation marks omitted). 

I respectfully dissent. 

—————— 

troubling. Even in SCRAP, the Court noted that what was required 

was “something more than an ingenious academic exercise in the 

conceivable,” 412 U. S., at 688, and we have since understood the 

allegation there to have been “that the string of occurrences alleged

would happen immediately,” Whitmore v. Arkansas, 495 U. S. 149, 159 

(1990) (emphasis added). That is hardly the case here. 

The Court says it is “quite wrong” to compare petitioners’ challenging 

“EPA’s parsimonious construction of the Clean Air Act to a mere 

‘lawyer’s game.’ ” Ante, at 24, n. 24. Of course it is not the legal challenge that is merely “an ingenious academic exercise in the conceivable,” SCRAP, supra, at 688, but the assertions made in support of 

standing. 
_________________ 

_________________ 

Cite as: 549 U. S. ____ (2007) 1 

SCALIA, J., dissenting 

SUPREME COURT OF THE UNITED STATES 

No. 05–1120 

MASSACHUSETTS, ET AL., PETITIONERS v. ENVIRONMENTAL PROTECTION AGENCY ET AL. 

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF

APPEALS FOR THE DISTRICT OF COLUMBIA CIRCUIT

[April 2, 2007]

 JUSTICE SCALIA, with whom THE CHIEF JUSTICE, 

JUSTICE THOMAS, and JUSTICE ALITO join, dissenting. 

I join THE CHIEF JUSTICE’s opinion in full, and would 

hold that this Court has no jurisdiction to decide this case 

because petitioners lack standing. The Court having 

decided otherwise, it is appropriate for me to note my

dissent on the merits. 

I 

A 

The provision of law at the heart of this case is 

§202(a)(1) of the Clean Air Act (CAA), which provides that

the Administrator of the Environmental Protection Agency

(EPA) “shall by regulation prescribe . . . standards applicable to the emission of any air pollutant from any class or 

classes of new motor vehicles or new motor vehicle engines, which in his judgment cause, or contribute to, air 

pollution which may reasonably be anticipated to endanger public health or welfare.” 42 U. S. C. §7521(a)(1) 

(emphasis added). As the Court recognizes, the statute

“condition[s] the exercise of EPA’s authority on its formation of a ‘judgment.’” Ante, at 30. There is no dispute that

the Administrator has made no such judgment in this 

case. See ante, at 32 (“We need not and do not reach the

question whether on remand EPA must make an endan-
2 MASSACHUSETTS v. EPA 

SCALIA, J., dissenting 

germent finding”); 68 Fed. 52929 (2003) (“[N]o Administrator has made a finding under any of the CAA’s regulatory provisions that CO2 meets the applicable statutory 

criteria for regulation”).

The question thus arises: Does anything require the 

Administrator to make a “judgment” whenever a petition

for rulemaking is filed? Without citation of the statute or 

any other authority, the Court says yes. Why is that so?

When Congress wishes to make private action force an 

agency’s hand, it knows how to do so. See, e.g., Brock v. 

Pierce County, 476 U. S. 253, 254–255 (1986) (discussing 

the Comprehensive Employment and Training Act 

(CETA), 92 Stat. 1926, 29 U. S. C. §816(b) (1976 ed., Supp. 

V), which “provide[d] that the Secretary of Labor ‘shall’ 

issue a final determination as to the misuse of CETA 

funds by a grant recipient within 120 days after receiving 

a complaint alleging such misuse”). Where does the CAA 

say that the EPA Administrator is required to come to a

decision on this question whenever a rulemaking petition

is filed? The Court points to no such provision because

none exists. 

Instead, the Court invents a multiple-choice question 

that the EPA Administrator must answer when a petition 

for rulemaking is filed. The Administrator must exercise 

his judgment in one of three ways: (a) by concluding that 

the pollutant does cause, or contribute to, air pollution

that endangers public welfare (in which case EPA is required to regulate); (b) by concluding that the pollutant 

does not cause, or contribute to, air pollution that endangers public welfare (in which case EPA is not required to 

regulate); or (c) by “provid[ing] some reasonable explanation as to why it cannot or will not exercise its discretion

to determine whether” greenhouse gases endanger public

welfare, ante, at 30, (in which case EPA is not required to 

regulate).

I am willing to assume, for the sake of argument, that 
Cite as: 549 U. S. ____ (2007) 3 

SCALIA, J., dissenting 

the Administrator’s discretion in this regard is not entirely 

unbounded—that if he has no reasonable basis for deferring judgment he must grasp the nettle at once. The 

Court, however, with no basis in text or precedent, rejects 

all of EPA’s stated “policy judgments” as not “amount[ing] 

to a reasoned justification,” ante, at 31, effectively narrowing the universe of potential reasonable bases to a single 

one: Judgment can be delayed only if the Administrator 

concludes that “the scientific uncertainty is [too] profound.” Ibid. The Administrator is precluded from concluding for other reasons “that it would . . . be better not to 

regulate at this time.” Ibid.1 Such other reasons— 

perfectly valid reasons—were set forth in the agency’s 

statement. 

“We do not believe . . . that it would be either effective 

or appropriate for EPA to establish [greenhouse gas] 

standards for motor vehicles at this time. As described in detail below, the President has laid out a 

comprehensive approach to climate change that calls 

for near-term voluntary actions and incentives along

with programs aimed at reducing scientific uncertainties and encouraging technological development so 

that the government may effectively and efficiently 

address the climate change issue over the long term. 

. . . . . 

“[E]stablishing [greenhouse gas] emission standards

for U. S. motor vehicles at this time would . . . result 

in an inefficient, piecemeal approach to addressing

the climate change issue. The U. S. motor vehicle 

fleet is one of many sources of [greenhouse gas] emissions both here and abroad, and different [greenhouse 

—————— 

1The Court’s way of putting it is, of course, not quite accurate. The 

issue is whether it would be better to defer the decision about whether to 

exercise judgment. This has the effect of deferring regulation but is 

quite a different determination. 
4 MASSACHUSETTS v. EPA 

SCALIA, J., dissenting 

gas] emission sources face different technological and 

financial challenges in reducing emissions. A sensible 

regulatory scheme would require that all significant 

sources and sinks of [greenhouse gas] emissions be

considered in deciding how best to achieve any needed 

emission reductions. 

“Unilateral EPA regulation of motor vehicle [greenhouse gas] emissions could also weaken U. S. efforts 

to persuade developing countries to reduce the 

[greenhouse gas] intensity of their economies. Considering the large populations and growing economies

of some developing countries, increases in their

[greenhouse gas] emissions could quickly overwhelm 

the effects of [greenhouse gas] reduction measures in

developed countries. Any potential benefit of EPA 

regulation could be lost to the extent other nations decided to let their emissions significantly increase in 

view of U. S. emissions reductions. Unavoidably, climate change raises important foreign policy issues, 

and it is the President’s prerogative to address them.” 

68 Fed. Reg. 52929–52931 (footnote omitted). 

The Court dismisses this analysis as “rest[ing] on reasoning divorced from the statutory text.” Ante, at 30. 

“While the statute does condition the exercise of EPA’s 

authority on its formation of a ‘judgment,’ . . . that judgment must relate to whether an air pollutant ‘cause[s], or

contribute[s] to, air pollution which may reasonably be

anticipated to endanger public health or welfare.’” Ibid. 

True but irrelevant. When the Administrator makes a 

judgment whether to regulate greenhouse gases, that

judgment must relate to whether they are air pollutants

that “cause, or contribute to, air pollution which may

reasonably be anticipated to endanger public health or 

welfare.” 42 U. S. C. §7521(a)(1). But the statute says 

nothing at all about the reasons for which the Administra-
Cite as: 549 U. S. ____ (2007) 5 

SCALIA, J., dissenting 

tor may defer making a judgment—the permissible reasons for deciding not to grapple with the issue at the

present time. Thus, the various “policy” rationales, ante, 

at 31, that the Court criticizes are not “divorced from the 

statutory text,” ante, at 30, except in the sense that the

statutory text is silent, as texts are often silent about

permissible reasons for the exercise of agency discretion. 

The reasons the EPA gave are surely considerations executive agencies regularly take into account (and ought to 

take into account) when deciding whether to consider

entering a new field: the impact such entry would have on

other Executive Branch programs and on foreign policy. 

There is no basis in law for the Court’s imposed limitation.

EPA’s interpretation of the discretion conferred by the 

statutory reference to “its judgment” is not only reasonable, it is the most natural reading of the text. The Court 

nowhere explains why this interpretation is incorrect, let

alone why it is not entitled to deference under Chevron 

U. S. A. Inc. v. Natural Resources Defense Council, Inc., 

467 U. S. 837 (1984). As the Administrator acted within 

the law in declining to make a “judgment” for the policy

reasons above set forth, I would uphold the decision to 

deny the rulemaking petition on that ground alone. 

B 

Even on the Court’s own terms, however, the same 

conclusion follows. As mentioned above, the Court gives

EPA the option of determining that the science is too 

uncertain to allow it to form a “judgment” as to whether

greenhouse gases endanger public welfare. Attached to 

this option (on what basis is unclear) is an essay requirement: “If,” the Court says, “the scientific uncertainty is so

profound that it precludes EPA from making a reasoned 

judgment as to whether greenhouse gases contribute to

global warming, EPA must say so.” Ante, at 31. But EPA 

has said precisely that—and at great length, based on 
6 MASSACHUSETTS v. EPA 

SCALIA, J., dissenting 

information contained in a 2001 report by the National

Research Council (NRC) entitled Climate Change Science:

An Analysis of Some Key Questions: 

“As the NRC noted in its report, concentrations of 

[greenhouse gases (GHGs)] are increasing in the atmosphere as a result of human activities (pp. 9–12). 

It also noted that ‘[a] diverse array of evidence points 

to a warming of global surface air temperatures’ (p.

16). The report goes on to state, however, that

‘[b]ecause of the large and still uncertain level of

natural variability inherent in the climate record and 

the uncertainties in the time histories of the various 

forcing agents (and particularly aerosols), a [causal]

linkage between the buildup of greenhouse gases in

the atmosphere and the observed climate changes

during the 20th century cannot be unequivocally established. The fact that the magnitude of the observed warming is large in comparison to natural

variability as simulated in climate models is suggestive of such a linkage, but it does not constitute proof 

of one because the model simulations could be deficient in natural variability on the decadal to century 

time scale’ (p. 17).

“The NRC also observed that ‘there is considerable 

uncertainty in current understanding of how the climate system varies naturally and reacts to emissions 

of [GHGs] and aerosols’ (p. 1). As a result of that uncertainty, the NRC cautioned that ‘current estimate of 

the magnitude of future warming should be regarded

as tentative and subject to future adjustments (either 

upward or downward).’ Id. It further advised that 

‘[r]educing the wide range of uncertainty inherent in 

current model predictions of global climate change

will require major advances in understanding and 

modeling of both (1) the factors that determine at-
Cite as: 549 U. S. ____ (2007) 7 

SCALIA, J., dissenting 

mospheric concentrations of [GHGs] and aerosols and

(2) the so-called “feedbacks” that determine the sensitivity of the climate system to a prescribed increase in 

[GHGs].’ Id. 

“The science of climate change is extraordinarily 

complex and still evolving. Although there have been

substantial advances in climate change science, there 

continue to be important uncertainties in our understanding of the factors that may affect future climate

change and how it should be addressed. As the NRC 

explained, predicting future climate change necessarily involves a complex web of economic and physical

factors including: Our ability to predict future global

anthropogenic emissions of GHGs and aerosols; the

fate of these emissions once they enter the atmosphere (e.g., what percentage are absorbed by vegetation or are taken up by the oceans); the impact of

those emissions that remain in the atmosphere on the

radiative properties of the atmosphere; changes in 

critically important climate feedbacks (e.g., changes in

cloud cover and ocean circulation); changes in temperature characteristics (e.g., average temperatures,

shifts in daytime and evening temperatures); changes

in other climatic parameters (e.g., shifts in precipitation, storms); and ultimately the impact of such 

changes on human health and welfare (e.g., increases 

or decreases in agricultural productivity, human 

health impacts). The NRC noted, in particular, that 

‘[t]he understanding of the relationships between 

weather/climate and human health is in its infancy 

and therefore the health consequences of climate 

change are poorly understood’ (p. 20). Substantial 

scientific uncertainties limit our ability to assess each

of these factors and to separate out those changes resulting from natural variability from those that are

directly the result of increases in anthropogenic 
8 MASSACHUSETTS v. EPA 

SCALIA, J., dissenting 

GHGs. 

“Reducing the wide range of uncertainty inherent in 

current model predictions will require major advances 

in understanding and modeling of the factors that determine atmospheric concentrations of greenhouse 

gases and aerosols, and the processes that determine 

the sensitivity of the climate system.” 68 Fed. Reg.

52930. 

I simply cannot conceive of what else the Court would like

EPA to say. 

II 

A 

Even before reaching its discussion of the word “judgment,” the Court makes another significant error when it

concludes that “§202(a)(1) of the Clean Air Act authorizes 

EPA to regulate greenhouse gas emissions from new motor 

vehicles in the event that it forms a ‘judgment’ that such

emissions contribute to climate change.” Ante, at 25 (emphasis added). For such authorization, the Court relies on 

what it calls “the Clean Air Act’s capacious definition of 

‘air pollutant.’” Ante, at 30. 

“Air pollutant” is defined by the Act as “any air pollution 

agent or combination of such agents, including any physical, chemical, . . . substance or matter which is emitted 

into or otherwise enters the ambient air.” 42 U. S. C. 

§7602(g). The Court is correct that “[c]arbon dioxide, 

methane, nitrous oxide, and hydrofluorocarbons,” ante, at 

26, fit within the second half of that definition: They are

“physical, chemical, . . . substance[s] or matter which [are]

emitted into or otherwise ente[r] the ambient air.” But the 

Court mistakenly believes this to be the end of the analysis. In order to be an “air pollutant” under the Act’s definition, the “substance or matter [being] emitted into . . . 

the ambient air” must also meet the first half of the definition—namely, it must be an “air pollution agent or combi-
Cite as: 549 U. S. ____ (2007) 9 

SCALIA, J., dissenting 

nation of such agents.” The Court simply pretends this 

half of the definition does not exist. 

The Court’s analysis faithfully follows the argument

advanced by petitioners, which focuses on the word “including” in the statutory definition of “air pollutant.” See 

Brief for Petitioners 13–14. As that argument goes, anything that follows the word “including” must necessarily

be a subset of whatever precedes it. Thus, if greenhouse

gases qualify under the phrase following the word “including,” they must qualify under the phrase preceding it. 

Since greenhouse gases come within the capacious phrase 

“any physical, chemical, . . . substance or matter which is 

emitted into or otherwise enters the ambient air,” they

must also be “air pollution agent[s] or combination[s] of 

such agents,” and therefore meet the definition of “air 

pollutant[s].”

That is certainly one possible interpretation of the 

statutory definition. The word “including” can indeed

indicate that what follows will be an “illustrative” sampling of the general category that precedes the word. 

Federal Land Bank of St. Paul v. Bismarck Lumber Co., 

314 U. S. 95, 100 (1941). Often, however, the examples 

standing alone are broader than the general category, and 

must be viewed as limited in light of that category. The 

Government provides a helpful (and unanswered) example: “The phrase ‘any American automobile, including any 

truck or minivan,’ would not naturally be construed to

encompass a foreign-manufactured [truck or] minivan.” 

Brief for Federal Respondent 34. The general principle 

enunciated—that the speaker is talking about American 

automobiles—carries forward to the illustrative examples

(trucks and minivans), and limits them accordingly, even

though in isolation they are broader. Congress often uses

the word “including” in this manner. In 28 U. S. C. 

§1782(a), for example, it refers to “a proceeding in a foreign or international tribunal, including criminal investi-
10 MASSACHUSETTS v. EPA 

SCALIA, J., dissenting 

gations conducted before formal accusation.” Certainly

this provision would not encompass criminal investigations underway in a domestic tribunal. See also, e.g., 2 

U. S. C. §54(a) (“The Clerk of the House of Representatives 

shall, at the request of a Member of the House of Representatives, furnish to the Member, for official use only, one 

set of a privately published annotated version of the 

United States Code, including supplements and pocket 

parts”); 22 U. S. C. §2304(b)(1) (“the relevant findings of 

appropriate international organizations, including nongovernmental organizations”).

In short, the word “including” does not require the

Court’s (or the petitioners’) result. It is perfectly reasonable to view the definition of “air pollutant” in its entirety:

An air pollutant can be “any physical, chemical, . . . substance or matter which is emitted into or otherwise enters 

the ambient air,” but only if it retains the general characteristic of being an “air pollution agent or combination of

such agents.” This is precisely the conclusion EPA 

reached: “[A] substance does not meet the CAA definition 

of ‘air pollutant’ simply because it is a ‘physical, chemical,

. . . substance or matter which is emitted into or otherwise 

enters the ambient air.’ It must also be an ‘air pollution 

agent.’” 68 Fed. Reg. 52929, n. 3. See also id., at 52928 

(“The root of the definition indicates that for a substance

to be an ‘air pollutant,’ it must be an ‘agent’ of ‘air pollution’”). Once again, in the face of textual ambiguity, the

Court’s application of Chevron deference to EPA’s interpretation of the word “including” is nowhere to be found.2 

—————— 

2Not only is EPA’s interpretation reasonable, it is far more plausible

than the Court’s alternative. As the Court correctly points out, “all

airborne compounds of whatever stripe,” ante, at 26, would qualify as

“physical, chemical, . . . substance[s] or matter which [are] emitted into

or otherwise ente[r] the ambient air,” 42 U. S. C. §7602(g). It follows 

that everything airborne, from Frisbees to flatulence, qualifies as an 

“air pollutant.” This reading of the statute defies common sense. 
Cite as: 549 U. S. ____ (2007) 11 

SCALIA, J., dissenting 

Evidently, the Court defers only to those reasonable interpretations that it favors. 

B 

Using (as we ought to) EPA’s interpretation of the definition of “air pollutant,” we must next determine whether

greenhouse gases are “agent[s]” of “air pollution.” If so, 

the statute would authorize regulation; if not, EPA would 

lack authority.

Unlike “air pollutants,” the term “air pollution” is not

itself defined by the CAA; thus, once again we must accept

EPA’s interpretation of that ambiguous term, provided its

interpretation is a “permissible construction of the statute.” Chevron, 467 U. S., at 843. In this case, the petition

for rulemaking asked EPA for “regulation of [greenhouse 

gas] emissions from motor vehicles to reduce the risk of

global climate change.” 68 Fed. Reg. 52925. Thus, in 

deciding whether it had authority to regulate, EPA had to 

determine whether the concentration of greenhouse gases 

assertedly responsible for “global climate change” qualifies as “air pollution.” EPA began with the commonsense 

observation that the “[p]roblems associated with atmospheric concentrations of CO2,” id., at 52927, bear little 

resemblance to what would naturally be termed “air 

pollution”: 

“EPA’s prior use of the CAA’s general regulatory 

provisions provides an important context. Since the 

inception of the Act, EPA has used these provisions to

address air pollution problems that occur primarily at 

ground level or near the surface of the earth. For example, national ambient air quality standards 

(NAAQS) established under CAA section 109 address 

concentrations of substances in the ambient air and 

the related public health and welfare problems. This 

has meant setting NAAQS for concentrations of ozone, 

carbon monoxide, particulate matter and other sub-
12 MASSACHUSETTS v. EPA 

SCALIA, J., dissenting 

stances in the air near the surface of the earth, not 

higher in the atmosphere. . . . CO2, by contrast, is 

fairly consistent in concentration throughout the 

world’s atmosphere up to approximately the lower 

stratosphere.” Id., at 52926–52927. 

In other words, regulating the buildup of CO2 and other 

greenhouse gases in the upper reaches of the atmosphere,

which is alleged to be causing global climate change, is not

akin to regulating the concentration of some substance 

that is polluting the air. 

We need look no further than the dictionary for confirmation that this interpretation of “air pollution” is eminently reasonable. The definition of “pollute,” of course, is 

“[t]o make or render impure or unclean.” Webster’s New 

International Dictionary 1910 (2d ed. 1949). And the first 

three definitions of “air” are as follows: (1) “[t]he invisible, 

odorless, and tasteless mixture of gases which surrounds 

the earth”; (2) “[t]he body of the earth’s atmosphere; esp.,

the part of it near the earth, as distinguished from the

upper rarefied part”; (3) “[a] portion of air or of the air 

considered with respect to physical characteristics or as

affecting the senses.” Id., at 54. EPA’s conception of “air 

pollution”—focusing on impurities in the “ambient air” “at

ground level or near the surface of the earth”—is perfectly 

consistent with the natural meaning of that term.

In the end, EPA concluded that since “CAA authorization to regulate is generally based on a finding that an air 

pollutant causes or contributes to air pollution,” 68 Fed.

Reg. 52928, the concentrations of CO2 and other greenhouse gases allegedly affecting the global climate are

beyond the scope of CAA’s authorization to regulate. 

“[T]he term ‘air pollution’ as used in the regulatory provisions cannot be interpreted to encompass global climate 

change.” Ibid. Once again, the Court utterly fails to

explain why this interpretation is incorrect, let alone so 
Cite as: 549 U. S. ____ (2007) 13 

SCALIA, J., dissenting 

unreasonable as to be unworthy of Chevron deference. 

* * * 

The Court’s alarm over global warming may or may not 

be justified, but it ought not distort the outcome of this 

litigation. This is a straightforward administrative-law 

case, in which Congress has passed a malleable statute

giving broad discretion, not to us but to an executive 

agency. No matter how important the underlying policy

issues at stake, this Court has no business substituting its 

own desired outcome for the reasoned judgment of the 

responsible agency.