Does the Clean Air Act grant the Environmental Protection Agency authority to regulate greenhouse gas emissions from new motor vehicles, and if so, can the EPA decline to exercise that authority based on policy considerations?

The Environmental Protection Agency (EPA) received a petition from a coalition of states, local governments, and private organizations to regulate greenhouse gas emissions from new motor vehicles under the Clean Air Act. The EPA denied this petition, asserting it lacked the statutory authority to regulate greenhouse gases and that, even if it possessed such authority, it would choose not to exercise it. Massachusetts, leading the petitioners, challenged this decision. The case revolves around the interpretation of Section 202(a)(1) of the Clean Air Act, which mandates the EPA Administrator to establish emission standards for 'any air pollutant' from motor vehicles that could reasonably be expected to endanger public health or welfare.

The EPA contended that carbon dioxide and other greenhouse gases do not fall under the definition of 'air pollutants' as specified in the Clean Air Act. Additionally, the case raises questions about standing, particularly whether states have special standing to sue the federal government over climate change-related issues.

Private organizations filed a rulemaking petition with the EPA, requesting regulation of greenhouse gas emissions from new motor vehicles. The EPA denied this petition. Subsequently, the petitioners, joined by states and local governments, sought review of the EPA's order in the United States Court of Appeals for the District of Columbia Circuit. The Court of Appeals denied the petition for review. The case then proceeded to the Supreme Court on a writ of certiorari.

(Stevens, J.)

Yes. The Clean Air Act grants the Environmental Protection Agency authority to regulate greenhouse gas emissions from new motor vehicles, and the EPA cannot decline to exercise that authority based solely on policy considerations. The Clean Air Act's definition of "air pollutant" is unambiguously broad enough to encompass greenhouse gases. This capacious language reflects Congress's intentional effort to confer regulatory flexibility, allowing the Act to address changing circumstances and scientific developments. The EPA's statutory mandate to protect public health and welfare is clear and unequivocal. Scientific uncertainty does not justify inaction; if uncertainty is so profound that it precludes reasoned judgment, the EPA must explicitly state this rationale. Policy concerns divorced from the statutory text are invalid grounds for refusing to regulate. The Act's precautionary and preventative orientation demands action in the face of credible threats, even before all scientific questions are fully resolved. Regulatory decisions must be grounded in the statute's text, structure, and purpose, not extraneous policy preferences. The EPA's core function is to apply its expertise to complex environmental issues and make reasoned judgments based on available scientific evidence. Failure to do so when faced with a significant environmental threat abdicates the agency's fundamental responsibility. This holding reinforces the principle that administrative agencies must act within the bounds of their statutory authority and cannot rewrite clear legislative directives to align with shifting political priorities or policy preferences.

Dissent (Roberts, C.J.) The petitioners lack standing to bring this case. The majority's "special solicitude" for state standing is unwarranted. The alleged harms are too speculative and generalized to meet the requirements for Article III standing. This expansion of standing doctrine undermines the separation of powers and invites the judiciary to overstep its constitutional role.

Dissent (Scalia, J.) The EPA's interpretation of the Clean Air Act was reasonable and should have been given deference under Chevron. The agency provided adequate reasons for declining to regulate greenhouse gases. The majority's decision improperly substitutes its own judgment for that of the agency, disregarding the EPA's expertise and discretion in environmental policymaking. This ruling sets a dangerous precedent for judicial overreach in complex regulatory matters.