Several states, local governments, and environmental organizations petitioned the EPA to regulate carbon dioxide and other greenhouse gas emissions from new motor vehicles under § 202(a)(1) of the Clean Air Act. EPA denied the petition, arguing in part that the Act did not authorize regulation of greenhouse gases for climate-change purposes and that, even if it had authority, it could decline to regulate for policy reasons. Massachusetts and other petitioners sought review in the D.C. Circuit, which upheld EPA’s denial. The Supreme Court granted certiorari to resolve both standing and the scope of EPA’s authority under the Act.
Does the Clean Air Act authorize EPA to regulate greenhouse gas emissions from new motor vehicles, and if so, may EPA refuse to decide whether such emissions endanger public health or welfare based on policy considerations outside the statute?
Under the Clean Air Act, EPA must regulate emissions of any “air pollutant” from new motor vehicles if, in its judgment, those emissions cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare. Greenhouse gases fit within the Act’s broad definition of “air pollutant,” and EPA may avoid regulation only if it determines they do not contribute to such endangerment or provides a reason grounded in the statute for declining to make that judgment.
Yes. The Court held that greenhouse gases are “air pollutants” under the Clean Air Act and that EPA’s denial of the rulemaking petition rested on impermissible reasons. EPA therefore had to ground its decision in the statutory endangerment framework rather than broad policy objections.
The Court first held that Massachusetts had standing because rising sea levels linked to climate change threatened the state’s sovereign coastal territory, and the risk was sufficiently concrete, traceable in part to EPA’s refusal to regulate, and partially redressable by reduced vehicle emissions. On the merits, the Court emphasized the Clean Air Act’s sweeping definition of “air pollutant,” which plainly encompassed carbon dioxide and other greenhouse gases. EPA’s reliance on policy concerns—such as scientific uncertainty, foreign-policy implications, and a preference for voluntary executive approaches—could not override the statute’s command. If EPA wished to decline regulation, it had to base that decision on whether greenhouse gases may reasonably be anticipated to endanger public health or welfare.
Chief Justice Roberts, joined by Justices Scalia, Thomas, and Alito, dissented on standing, arguing the alleged climate injuries were too generalized and not sufficiently traceable or redressable. Justice Scalia, joined by the same Justices, also dissented on the merits, contending EPA had discretion in interpreting the statute and in declining to regulate.
Massachusetts v. EPA is a foundational administrative and environmental law case because it confirmed that greenhouse gases are covered by the Clean Air Act and compelled EPA to confront climate regulation through the statute’s endangerment framework. It is the basis for EPA’s subsequent greenhouse-gas endangerment finding and many later climate rules. Closely related cases include Utility Air Regulatory Group v. Environmental Protection Agency, 573 U.S. 302 (2014), American Electric Power Co. v. Connecticut, 564 U.S. 410 (2011), and West Virginia v. Environmental Protection Agency, 597 U.S. 697 (2022).
Utility Air Regulatory Group v. Environmental Protection Agency, 573 U.S. 302 (2014) |
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American Electric Power Co. v. Connecticut, 564 U.S. 410 (2011) |
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West Virginia v. Environmental Protection Agency, 597 U.S. 697 (2022) |
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