Massachusetts v. EPA
Whether the Environmental Protection Agency has the authority under the Clean Air Act to regulate greenhouse gas emissions from new motor vehicles, and whether its refusal to do so was lawful.
The Decision
5-4 decision · Opinion by John Paul Stevens · 2007
Majority Opinion— John Paul Stevensconcurring ↓dissent ↓
In a 5–4 decision authored by Justice John Paul Stevens, the Supreme Court ruled in favor of Massachusetts and reversed the D.C. Circuit. The Court held that the EPA does have statutory authority to regulate greenhouse gas emissions from new motor vehicles under the Clean Air Act, and that the agency's stated reasons for refusing to exercise that authority were insufficient under the law.
On the threshold question of standing, the Court found that Massachusetts had demonstrated a concrete and particularized injury. The majority gave 'special solicitude' to the state's standing as a quasi-sovereign entity, noting that Massachusetts owned a great deal of coastal land that was being lost to rising sea levels — a harm directly tied to climate change and traceable in part to greenhouse gas emissions from motor vehicles. The Court acknowledged that climate change is caused by many sources worldwide, but held that a litigant does not need to show that a favorable court ruling would entirely solve the problem — only that it would reduce the harm to some degree. Regulating vehicle emissions would slow the pace of climate change and thereby reduce the injury to Massachusetts.
On the merits, the Court found that the Clean Air Act's definition of 'air pollutant' is capacious and unambiguous: it covers 'any air pollution agent… including any physical, chemical, biological, radioactive substance or matter which is emitted into or otherwise enters the ambient air.' Carbon dioxide and other greenhouse gases clearly fit this definition. The Court rejected the EPA's argument that Congress could not have intended such a broad grant of authority, noting that the statute's plain language admits of no exception for greenhouse gases.
Finally, the Court held that the EPA's refusal to regulate was arbitrary and capricious. Under Section 202(a)(1), the EPA must make a judgment about whether greenhouse gas emissions from new vehicles contribute to air pollution that may endanger public health or welfare. The agency can only decline to regulate if it concludes that greenhouse gases do not contribute to climate change, or if it provides a scientifically grounded reason for its inability to make a determination. The policy considerations the EPA had cited — diplomatic strategy, the desire for more research, the existence of voluntary programs — were not among the statutory grounds for refusing to act. The Court remanded the case to the EPA with instructions to reassess the petition under the proper legal framework.
Concurring Opinions
There were no separately written concurring opinions in this case; all five justices in the majority joined Justice Stevens's opinion in full.
Dissenting Opinions
John G. Roberts Jr.joined by Antonin Scalia, Clarence Thomas, Samuel Alito
Chief Justice Roberts argued that Massachusetts lacked standing to bring the case because the alleged injury from climate change was too generalized, speculative, and not meaningfully redressable by a court order directed at the EPA. He contended the majority stretched standing doctrine beyond recognition by granting states special treatment and by accepting a highly attenuated causal chain between vehicle emissions, global climate change, and harm to Massachusetts's coastline.
- The claimed injury — loss of coastal land to rising sea levels caused by global climate change — was not the kind of particularized, concrete harm that Article III standing requires; it was a generalized grievance shared by the entire world.
- Even if the EPA began regulating U.S. vehicle emissions, the effect on global greenhouse gas concentrations would be so minimal as to provide no meaningful redress for the petitioners' alleged injuries, particularly given that massive emissions from countries like China and India would continue unchecked.
- The majority's concept of 'special solicitude' for state litigants in standing analysis had no basis in prior case law and improperly relaxed the constitutional requirements for bringing suit in federal court.
Antonin Scaliajoined by John G. Roberts Jr., Clarence Thomas, Samuel Alito
Justice Scalia wrote separately to challenge the majority on the merits, arguing that the EPA reasonably interpreted the Clean Air Act as not covering greenhouse gases in the context of climate change, and that even if it did have such authority, the agency lawfully exercised its discretion in declining to regulate. He argued the majority improperly substituted its own judgment for the agency's expert policy determination.
- The Clean Air Act was designed to address conventional air pollutants that cause localized health and environmental harms, and reading it to encompass the global phenomenon of climate change was an unreasonable expansion of the statute that Congress never intended.
- The EPA's decision to decline regulation involved a complex balancing of scientific uncertainty, economic consequences, and foreign policy considerations — exactly the kind of expert agency judgment that courts should defer to rather than second-guess.
- The word 'judgment' in Section 202(a)(1) grants the EPA Administrator broad discretion to weigh a range of factors, not merely to make a binary scientific determination about endangerment, and the majority's narrow reading of that discretion was incorrect.
Background & Facts
In October 1999, a coalition of nineteen private environmental and conservation organizations filed a rulemaking petition asking the Environmental Protection Agency (EPA) to regulate greenhouse gas emissions — particularly carbon dioxide — from new motor vehicles. They relied on Section 202(a)(1) of the Clean Air Act, which directs the EPA Administrator to set emission standards for any air pollutant from new motor vehicles that, in the Administrator's judgment, 'cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.' The petitioners argued that the science linking greenhouse gases to global warming and climate change was overwhelming, and that the EPA had a legal duty to act.
In September 2003, after a change in presidential administrations, the EPA denied the petition on two grounds. First, the agency argued that the Clean Air Act did not actually give it authority to regulate carbon dioxide or other greenhouse gases for climate change purposes. Second, even assuming it did have such authority, the EPA said it would be unwise to exercise it at that time. The agency pointed to scientific uncertainty about the precise link between greenhouse gases and climate change, ongoing voluntary industry programs to reduce emissions, and concern that unilateral regulation might interfere with the President's broader foreign policy approach to climate change negotiations.
Massachusetts, joined by eleven other states, several local governments, and multiple environmental organizations, challenged the EPA's denial in the U.S. Court of Appeals for the District of Columbia Circuit. In a fractured 2-1 decision, the D.C. Circuit upheld the EPA's refusal, though the three judges on the panel each wrote separate opinions and disagreed sharply on both the standing question and the merits. One judge found the EPA had broad discretion to decline regulation; another found the petitioners lacked standing; and the dissenting judge argued the EPA had clear authority and an obligation to regulate.
The Supreme Court agreed to hear the case because of the enormous importance of the underlying legal and policy questions — whether federal environmental law covers greenhouse gases and whether the EPA can decline to regulate pollutants based on policy considerations beyond the statutory text. The case was argued in November 2006 and decided in April 2007.
The Arguments
Massachusetts argued that greenhouse gases, including carbon dioxide, plainly fall within the Clean Air Act's sweeping definition of 'air pollutant,' and that the EPA was required by statute to determine whether those emissions endanger public health or welfare. The state further argued that it had standing to bring the case because rising sea levels caused by climate change posed a direct, concrete threat to its coastal territory.
- The Clean Air Act defines 'air pollutant' extremely broadly 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,' which easily encompasses greenhouse gases like carbon dioxide.
- As a sovereign state with quasi-sovereign interests in its territory, Massachusetts faced a particularized injury: rising sea levels driven by climate change were already eroding its coastline and would continue to do so, representing a concrete and imminent harm traceable to unregulated vehicle emissions.
- The EPA's policy-based reasons for declining to regulate — such as not wanting to interfere with the President's diplomatic strategy on climate change — were not among the grounds the statute allows for refusing to act, making the denial arbitrary and contrary to law.
The EPA argued that the Clean Air Act was never intended to cover greenhouse gases linked to climate change, and that even if it did have such authority, the agency retained broad discretion to decline rulemaking for legitimate policy reasons. The EPA also contended that the petitioners lacked standing because climate change is too diffuse and generalized an injury to support a lawsuit by any single party.
- Congress did not intend the Clean Air Act to address global climate change, a problem fundamentally different from traditional air pollution, and granting EPA such sweeping authority would have enormous economic and political consequences that Congress would not have delegated silently.
- Even if the EPA had authority to regulate greenhouse gases, the statute grants the Administrator discretion in deciding whether to make an endangerment finding, and the agency's decision to prioritize voluntary measures, further scientific research, and diplomatic approaches was a reasonable exercise of that discretion.
- The petitioners could not demonstrate the concrete, particularized, and redressable injury required by Article III standing doctrine, because climate change is a global phenomenon caused by innumerable sources worldwide, and regulating U.S. vehicle emissions alone would not meaningfully address the petitioners' alleged harms.