Massachusetts v. Environmental Protection Agency, 549 U.S. 497 (2007)
Massachusetts v. EPA is a landmark Supreme Court decision that reshaped federal environmental regulation by recognizing greenhouse gases as pollutants subject to the Clean Air Act.
1) Do petitioners, including the Commonwealth of Massachusetts, have Article III standing to challenge EPA's denial of the rulemaking petition? 2) Does the Clean Air Act authorize EPA to regulate greenhouse gases from new motor vehicles? 3) Did EPA lawfully decline to regulate based on policy considerations and scientific uncertainty unrelated to the statutory endangerment inquiry?
Article III standing requires a concrete and particularized injury that is fairly traceable to the challenged conduct and likely to be redressed by a favorable decision; states receive special solicitude where Congress has afforded a procedural right to challenge agency action or inaction. Under CAA § 202(a)(1), EPA must regulate emissions of any air pollutant from new motor vehicles that, in its judgment, cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. The definitions of air pollutant and welfare are broad and encompass greenhouse gases and climate effects. An agency's denial of a rulemaking petition is reviewable under the Administrative Procedure Act and must be grounded in the statute; an agency may not rely on extraneous policy preferences to avoid making the judgment Congress required, and its decision must not be arbitrary and capricious, 5 U.S.C. § 706(2)(A).
Yes, Massachusetts and other petitioners have standing to challenge EPA's denial. Yes, the Clean Air Act authorizes EPA to regulate greenhouse gases as air pollutants under § 202(a)(1). EPA's denial of the petition was unlawful because it rested on reasons not permitted by the statute; EPA must either make an endangerment finding or explain, based on the scientific record, why it cannot make such a judgment. The Court reversed and remanded.
Massachusetts v. EPA is the foundation of federal climate regulation. It confirmed that greenhouse gases are pollutants under the CAA, required EPA to evaluate endangerment based on science, and spurred the 2009 endangerment finding and subsequent motor-vehicle greenhouse gas standards. The decision also reshaped standing doctrine by recognizing states' special solicitude and the sufficiency of incremental, risk-reducing relief. For administrative law, it underscores that agencies must adhere to statutory directives and cannot invoke broad policy or uncertainty to avoid making required judgments. The case has influenced later climate and administrative decisions, including American Electric Power v. Connecticut (displacement of federal common law by the CAA) and Utility Air Regulatory Group v. EPA (limits on permitting for greenhouse gases).