The Roberts Court ruled in Massachusetts v. Environmental Protection Agency (2006) that several states, local governments, and private organizations had the standing to challenge the controversial decision made by the federal Environmental Protection Agency (EPA) to not exercise its powers under the federal Clean Air Act to determine whether emissions of gases such as carbon dioxide contribute to global warming. The EPA had declined to regulate the emissions of such gases, saying that such a course of action may hamper the president’s “comprehensive approach” to the problem.

A sharply divided Supreme Court ruled 5–4 that the state of Massachusetts and the other plaintiffs had the standing to challenge the EPA’s inaction. “EPA’s steadfast refusal to regulate greenhouse gas emissions presents a risk of harm to Massachusetts that is both ‘actual’ and ‘imminent,’” wrote Justice John Paul Stevens for the majority. Stevens reasoned that the challengers certainly had the legal right to challenge the EPA’s decision to terminate the rulemaking process on this important issue of global warming.