Supreme Court Rules Greenhouse Gases Are Air Pollutants in Mass. v. EPA

The Supreme Court ruled 5-4 in Massachusetts v. EPA that greenhouse gases qualify as air pollutants under the Clean Air Act, forcing EPA to regulate carbon dioxide if it finds an endangerment to public health. Justice John Paul Stevens wrote the majority opinion joined by Kennedy, Souter, Ginsburg, and Breyer. The Court rejected EPA's claim that climate policy reasons could justify refusing to regulate.