Massachusetts v. EPA

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Multi-state challenge to EPA denial of petition to regulate greenhouse gas emissions from motor vehicles under Clean Air Act.

Citation: Massachusetts v. EPA, 549 U.S. 497 (2007)

Topic: Climate Change Mitigation

Type of action: Lawsuit v. Federal Government

States involved: California, Connecticut, District of Columbia, Illinois, Maine, Massachusetts, New Jersey, New Mexico, New York, Oregon, Rhode Island, Vermont, Washington

Summary: States, local governments, and environmental organizations petitioned for review of an EPA order denying a petition for rulemaking to regulate greenhouse gas (GHG) emissions from motor vehicles under the Clean Air Act (CAA). Two key issues were: (1) whether EPA had statutory authority to regulate GHG emissions under the CAA, and (2) whether EPA could decline to regulate GHG emissions based on policy judgments that fall outside the scope of the regulatory considerations outlined in the CAA. The Supreme Court held that EPA did have statutory authority to regulate because carbon dioxide and other GHGs fall within the CAA’s capacious definition of “air pollutant” and that EPA cannot deny a petition to regulate on grounds that are not enumerated in the CAA. The court remanded to EPA, instructing the agency to either issue an endangerment finding for GHGs or provide a basis for not issuing the endangerment finding that is grounded in the statute.

On remand, EPA issued a positive endangerment finding that GHGs from motor vehicles do endanger public health and welfare.

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