U.S. Supreme Court Rules EPA May Regulate Greenhouse Gas Emissions

In a 5-4 decision in Massachusetts v. EPA, the United States Supreme Court ruled that the Environmental Protection Agency (EPA) has the authority to promulgate regulations of greenhouse gas emissions, including carbon dioxide from vehicles.

The Court further held that EPA’s failure to do so in response to a rulemaking petition from the State of Massachusetts, without providing sufficient explanation, was arbitrary and capricious, and violated the law.

The Court found that the Clean Air Act’s (CAA) broad definition of “air pollutant,” as any physical or chemical substance emitted into the ambient air, included carbon dioxide and other greenhouse gases. Since greenhouse gases are covered by the CAA, EPA is required to make a reasoned judgment on whether or not to issue regulations. EPA can avoid promulgating greenhouse gas emission regulations, “only if it determines that greenhouse gases do not contribute to climate change, or if it provides some reasonable explanation as to why it cannot or will not exercise its discretion to determine whether they do.” The Court did not consider that the policy judgments relied upon by EPA provided a “reasonable explanation” for not promulgating regulations.

Noting that the harms associated with climate change are serious and well recognized, the Court held that Massachusetts established it would suffer an actual and imminent injury due to the impact on its coastline of a rise in global sea levels resulting from global warming. The court further noted that EPA’s regulations could address these injuries by reducing emissions and slowing the pace of global warming.

Since the Court ruled that EPA may regulate greenhouse gases under existing law (the CAA), new federal regulation may result without congressional action. The decision also may result in federal regulation of greenhouse gas emissions from non-vehicle sources. Moreover, the opinion may spur passage of new climate change law. The ruling may also influence EPA’s decision on California’s pending request for a waiver to allow the state to regulate greenhouse gas emissions from vehicles, and be used by California to defend against lawsuits challenging the state’s greenhouse gas emissions laws.