Massachusetts v. EPA

Facts

States, local governments, and environmental organizations petitioned for review of an order of the Environmental Protection Agency (EPA) denying a petition for rulemaking to regulate greenhouse gas emissions from motor vehicles under the Clean Air Act. The statute mandates such regulations if certain prerequisites are met. A rise in global temperatures has coincided with a significant increase in the concentration of carbon dioxide in the atmosphere. Calling global warming the most pressing environmental challenge of our time, a group of States, local governments, and private organizations alleged in a petition for certiorari that the Environmental Protection Agency has abdicated its responsibility under the Clean Air Act to regulate the emissions of greenhouse gases. Petitioners asked us to answer two questions: whether EPA has the statutory authority to regulate greenhouse gas emissions from new motor vehicles and if so whether its stated reasons for refusing to do so are consistent with the statute.