American Electric Power Co. v. Connecticut

Background

Several States, the city of New York, and three private land trusts sued four private power companies and the federally owned Tennessee Valley Authority. They said those companies’ carbon‑dioxide emissions contribute to global warming and sought court orders capping each defendant’s emissions and requiring annual reductions. The cases began before EPA began rulemaking on greenhouse gases and were combined in federal court in New York.

Reasoning

The central question was whether federal courts may use the federal common law of public nuisance to force major emitters to limit carbon‑dioxide emissions. The Court explained that the Clean Air Act gives EPA the authority to regulate greenhouse gases and to set performance standards for sources like powerplants. Because Congress assigned EPA that decisionmaking role, the statute “speaks directly” to the issue and displaces the federal common‑law claims the plaintiffs sought. The Court said judges lack the institutional tools and the statutory mandate to set nationwide emissions limits that EPA is empowered to design and implement.

Real world impact

The ruling bars the specific federal common‑law lawsuits asking courts to impose nationwide caps and reductions on the named power companies. It leaves regulation of greenhouse gases primarily to EPA and the state regulatory process, subject to judicial review of EPA actions. The Court declined to decide whether state-law nuisance claims remain available and left that question open for the lower courts on remand.