Today, the U.S. Supreme Court ruled in American Electric Power v. Connecticut that federal common law nuisance claims cannot be used to address harms arising from climate change. In 2004, eight states, New York City, and three nonprofit land trusts filed public nuisance complaints in federal district court against the nation’s largest emitters of carbon dioxide, seeking to slash power-plant greenhouse gas (“GHG”) emissions in 20 states. The district court dismissed the suits, claiming that they presented nonjusticiable political questions. However, last year the Second Circuit reversed and ruled that the case could proceed. Justice Sonia Sotomayor did not take part in today’s decision because she wrote the Second Circuit opinion that rejected the defendants’ political question defense.

In a much-anticipated decision, the Court reversed the Second Circuit and unanimously held that the federal common law of nuisance is “displaced” by the Clean Air Act’s (“CAA”) grant of jurisdiction to the U.S. Environmental Protection Agency (“EPA”) to regulate GHGs. Such displacement occurs when a federal statute “speaks directly” to the issue raised by the federal common law claims. The Court stressed that the standard for displacement of federal common law is less rigorous than the standard for preemption of state law claims.

Although the Court unequivocally rejected federal common law claims for GHG harms, the Court’s split decision as to the jurisdictional issues of standing and the political question doctrine may still permit future state lawsuits challenging environmental impacts of GHG emissions. The Court remanded to the Second Circuit so that it might evaluate whether state law claims are preempted by the Clean Air Act, an issue not addressed by the parties.