Does the Clean Air Act, together with the EPA action it authorizes, displace a federal common law public nuisance claim seeking abatement of carbon-dioxide emissions from fossil-fuel fired power plants?

In July 2004, two groups of plaintiffs filed separate complaints in the Southern District of New York against the same five major electric power companies: four private companies and the Tennessee Valley Authority, a federally owned corporation operating fossil-fuel fired power plants in several States. The first group included eight States and New York City; the second consisted of three nonprofit land trusts. The complaints alleged that the defendants are the five largest emitters of carbon dioxide in the United States, with collective annual emissions of 650 million tons, representing 25 percent of emissions from the domestic electric power sector, 10 percent of emissions from all domestic human activities, and 2.5 percent of anthropogenic emissions worldwide.

The plaintiffs asserted that by contributing to global warming, the defendants' emissions created a substantial and unreasonable interference with public rights, in violation of the federal common law of interstate nuisance or, alternatively, state tort law. The States and New York City alleged risks to public lands, infrastructure, and health; the trusts alleged that climate change would destroy habitats on land they conserved. All plaintiffs sought injunctive relief requiring each defendant to cap its carbon dioxide emissions and then reduce them by a specified percentage each year for at least a decade. These suits began before the EPA initiated efforts to regulate greenhouse gases following Massachusetts v. EPA.

The District Court dismissed both suits as presenting non-justiciable political questions. The Second Circuit reversed, holding that the suits were not barred by the political question doctrine, that the plaintiffs had adequately alleged Article III standing, and that all plaintiffs had stated a claim under the federal common law of nuisance. The Second Circuit further held that the Clean Air Act did not displace federal common law because the EPA had not yet promulgated any rule regulating greenhouse gases. The Supreme Court granted certiorari.

(Ginsburg, J.)

Yes. The Clean Air Act and the EPA action the Act authorizes displace any federal common law right to seek abatement of carbon-dioxide emissions from fossil-fuel fired power plants. (On jurisdiction, the Court affirmed the Second Circuit's exercise of jurisdiction by an equally divided vote on Article III standing, with four Justices finding standing under Massachusetts v. EPA and four finding none.)

When Congress addresses a question previously governed by federal common law, the need for such an unusual exercise of lawmaking by federal courts disappears. Milwaukee v. Illinois, 451 U.S. 304 (1981) (Milwaukee II). Displacement does not require the clear and manifest congressional purpose demanded for preemption of state law; the test is simply whether the statute speaks directly to the question at issue. Mobil Oil Corp. v. Higginbotham, 436 U.S. 618 (1978). Massachusetts established that carbon dioxide is an air pollutant subject to regulation under the Act, and the Act speaks directly to emissions from the defendants' plants. Section 111 directs the EPA to list categories of stationary sources that contribute significantly to dangerous air pollution, set performance standards for new or modified sources, and, through §7411(d), regulate existing sources. The Act provides multiple enforcement avenues, including EPA enforcement, citizen suits, and petitions for rulemaking reviewable in federal court. The Act thus provides a means to seek the same relief the plaintiffs seek, leaving no room for a parallel common-law track.

Federal common law is displaced even before the EPA sets standards. The question is whether the field has been occupied, not whether it has been occupied in a particular manner. Milwaukee II. Congress delegated to the EPA the decision whether and how to regulate carbon-dioxide emissions from power plants, and that delegation displaces federal common law. Even if the EPA declined to regulate, courts could not use nuisance law to upset that determination, which remains reviewable under the Act's arbitrary-and-capricious standard. The expert agency is better equipped than federal judges to balance environmental benefits against energy needs and economic disruption.

The state-law nuisance claims were not decided; their availability depends on the preemptive effect of the Act, which was unbriefed, and is left for remand. The judgment is reversed and remanded.

Concurring in part and concurring in the judgment (Alito, J., joined by Thomas, J.) Agrees with the Court's displacement analysis only on the assumption, made for the sake of argument because no party contends otherwise, that the interpretation of the Clean Air Act adopted in Massachusetts v. EPA is correct.