Massachusetts v. EPA
549 U.S. 497 (2007)

Annotate this Case
  • Syllabus  | 
  • Opinion (John Paul Stevens)  | 
  • Dissent (John G. Roberts, Jr.)  | 
  • Dissent (Antonin Scalia)




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 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.


   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 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 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 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 pre-existing 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.

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.

Primary Holding
The Clean Air Act allows the Environmental Protection Agency to regulate greenhouses gases because they qualify as air pollutants. Also, standing requires showing a concrete harm that can be traced to the defendant and remedied by the courts.
Twelve states as well as various cities and organizations sought to require the Environmental Protection Agency (EPA) to regulate greenhouse gases like carbon dioxide under its authority to regulate pollutants. The lawsuit was based on Section 202(a)(1) of the Clean Air Act, a provision that requires the EPA Administrator to set emission standards for air pollutants from motor vehicles that the Administrator judges to play a role in pollution that could be reasonably expected to endanger public health or welfare.

Responding to that mandate, the EPA had decided that it lacked authority to regulate greenhouse gases like carbon dioxide for climate change purposes. Even if it did have that authority, it felt that it was unnecessary to set greenhouse gas emissions standards for vehicles. The case combined the substantive issue of whether the agency had decided correctly on these issues with the procedural question of whether the states, cities, and organizations even had standing to bring such a claim. The concrete injury that they alleged was the loss of coastline to rising sea levels in global warming.

Procedural History

U.S. Court of Appeals for the District of Columbia Circuit - 415 F.3d 50 (D.C. Cir. 2005)

Judgment for defendants affirmed. In a disjointed decision, some Justices would have dismissed the claim for lack of standing to sue, while other Justices who found that there was standing but that the claim failed on the merits. The question of whether there was a sufficiently concrete injury to any of the plaintiffs would be raised again at the Supreme Court.

  • James Milkey (plaintiffs)



  • John Paul Stevens (Author)
  • Anthony M. Kennedy
  • David H. Souter
  • Ruth Bader Ginsburg
  • Stephen G. Breyer

After finding that the states had standing for these types of environmental claims, Stevens wrote that the Clean Air Act does provide sufficient statutory authority for the agency to regulate greenhouse gases. Stevens pointed out that the law provides a sweeping definition of what constitutes a pollutant, and greenhouse gases like carbon dioxide clearly fit inside that definition. He sent the case back to the agency for a reconsideration of its decision. While its current reasoning for not regulating greenhouse gases was insufficient, it would have the chance to find another reasonable basis for that policy.


  • John G. Roberts, Jr. (Author)
  • Antonin Scalia
  • Clarence Thomas
  • Samuel A. Alito, Jr.

Arguing that the states lacked standing, Roberts felt that the loss of land to rising sea levels in coastal areas was not a sufficiently concrete injury. He also found that there was a lack of scientific evidence to support the notion that EPA regulations would have a meaningful impact in controlling global warming. This meant that there was not a causal nexus between the actions of the EPA and the harm to the states. Roberts pointed out that much of the impetus behind global warming comes from foreign nations that have no environmental regulations.


  • Antonin Scalia (Author)
  • John G. Roberts, Jr.
  • Clarence Thomas
  • Samuel A. Alito, Jr.

Picking up where Roberts left off, Scalia agreed that the plaintiffs lacked standing but proceeded to address the merits of the case as though they did. He found that the statute did not deny the agency the authority to defer its decision on regulations in the area until a later date. He also agreed with Roberts that the scientific evidence supporting the claims of the states was too speculative to take seriously. Scalia argued that the majority had abandoned the principle of deference to agency decision-making that was articulated in Chevron v. Natural Resources Defense Council (1984).

Case Commentary

When it reconsidered the matter, the EPA reversed its decision and found that regulating greenhouse gases had a reasonable connection to protecting public health and welfare. It stated that greenhouse gases like carbon dioxide had played a key role in global warming. Challenges by states that opposed more aggressive agency regulations did not survive review by the D.C. Circuit.

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