The Appellees—eight States, New York City, and three nonprofit land trusts—filed complaints asserting that the Appellants—four private companies and the Tennessee Valley Authority—violated the federal common law of interstate nuisance, or in the alternative, state tort law, by emitting carbon dioxide into the air. Because the parties did not brief the state tort law action, the Supreme Court only addressed the federal common law action.

Justice Ginsburg’s opinion for the Court explained that after Erie R. Co. v. Tompkins, where the Court eliminated what was known as federal common law, a “new” federal common law emerged to address subjects within national legislative power. Am. Elec. Power Co. v. Conn., No. 10-174, slip op. at 7 (U.S. June 20, 2011). One of those areas is environmental protection. As such, several States have brought law suits under this common law to abate pollution emanating from another State. Appellees alleged that they could bring a similar suit.

Resembling State law preemption, Congressional action can overcome federal common law. Id. at 9. Federal common law does not require, however, the same clear and manifest intent from the legislation that State law preemption does. Id. To dispel federal common law, a Congressional statute merely must tackle the same issue as the common law. Id. at 10.

Applying the test, the Supreme Court found that Congress’ Clean Air Act displaced any federal common law addressing the appellees’ claims. The Court provided a detailed description of the Clean Air Act provisions that covered greenhouse gas emissions, but Massachusetts v. EPA truly compelled this result. That case, decided in 2007, explicitly found that the Clean Air Act addressed greenhouse gas emissions. The Act delegated the regulation of these emissions to the Environmental Protection Agency (“EPA”). Massachusetts v. EPA, 549 U.S. 497, 528–29 (2007).

Appellees insisted that it takes more than enactment of a law: the governmental agency that Congress gives regulatory authority must exercise that authority to dispel federal common law. The Court disagreed, finding that Congressional action controlled, not the promptness or harshness of the governmental agency’s implementation of the legislation. That the EPA might not regulate as much as plaintiffs would like, or possibly is needed, is immaterial. Once Congress has delegated authority, the courts will only step in if an agency’s actions are arbitrary, capricious, an abuse of discretion, or outside the law. Because Congress had delegated the authority to regulate greenhouse gas emissions to the EPA, the appellees could not bring a federal common law action against alleged greenhouse gas emitters.