In a unanimous ruling (8-0), the Supreme Court held that the Clean Air Act (CAA) and EPA’s implementation of the Act displace any federal common-law claims against carbon dioxide emitters, even though there is currently no regulation for the substance. American Electric Power v. Connecticut, No. 10-174, 2011 WL 2437011 (June 20, 2011). Justice Ginsburg wrote for the Court and was joined by Justices Roberts, Scalia, Kennedy, Breyer, and Kagan. Justice Alito wrote a separate opinion, concurring in part and concurring in the opinion, which Justice Thomas joined. Justice Sotomayor was recused.
Two groups of plaintiffs, the first consisting of eight states (including the respondent) and New York City, the second consisting of three nonprofit land trusts, sued five major electric power companies (including the petitioner), sought a decree setting annual carbon dioxide emissions limits for each defendant, to be reduced each year. The District Court dismissed both cases, citing “non-justiciable political questions,” but the Second Circuit reversed the motions to dismiss, finding that the plaintiffs had Article III standing and that they had stated a claim under the federal common law of nuisance.
After a divided Supreme Court held that at least one plaintiff could proceed with the lawsuit, the full Court reversed the Second Circuit’s ruling, holding that the CAA and EPA’s implementation of the act displaced any federal common law claims related to carbon dioxide limits. Relying on Milwaukee v. Illinois (Milwaukee II), it noted that the standard for finding legislative displacement of federal common law is less stringent than that for finding preemption (451 U.S. 304, 317(1981)). It cited provisions of the CAA and its holding in Massachusetts v. EPA, 549 U.S. 497 (2007) that the EPA has the authority to regulate greenhouse gases to conclude that the only remedy available to states and private parties would be to petition for a rulemaking, after which federal courts can review EPA’s response.
The Court noted further that this displacement applies regardless of whether a regulation currently exists. It cited Milwaukee II again to declare that displacement does not depend on how a field has been occupied 451 U.S., at 324. Specifically, it pointed to Middlesex County Sewerage Authority v. National Sea Clammers Assn., in which it held that federal common law was displaced, even though the authorizing legislation allows emissions until EPA acts (453 U. S. 1, 22, n. 32 (1981)). In addition, the Court supported its ruling by remarking that the legislation prescribes that judicial review follows agency action and that an expert agency is more qualified than individual district judges to set limits on emissions.
The Court declined to address whether the plaintiffs’ nuisance claims under respective state laws are preempted and left this question for reconsideration on remand. (The Second Circuit had decided that the state law claims were preempted because the suits were allowed under federal common law.) Separately, it also declined to consider whether a federal common-law claim would exist for greenhouse gas emissions abatement if not for the CAA, despite the parties’ arguments on this point.
Justice Alito, joined by Justice Thomas, filed a one-paragraph opinion concurring in the judgment, and concurring with the Court’s displacement analysis, contingent on the interpretation of the CAA in Massachusetts v. EPA, which was not challenged by the parties.