Over the past year, several cities and counties have brought common law actions for activity they claim causes climate change, targeting both in-state and out-of-state sources. Does state common law reach this far?

The Constitution delegates to Congress the power to regulate interstate commerce. By contrast, a state’s police powers do not extend beyond its borders. For this reason, the Supreme Court has accepted “federal” common law to address interstate pollution. Missouri v. Illinois, 180 U.S. 208, 241 (1901). As the Court observed, “[i]f state law can be applied, there is no need for federal common law; if federal common law exists, it is because state law cannot be used.” City of Milwaukee v. Illinois, 451 U.S. 304, 314 n.7 (1981) (Milwaukee II). Confirming the limited reach of state common law, the Court has held that the Clean Water Act “precludes a court from applying the law of an affected state against an out-of-state source.” Int’l Paper Co. v. Ouellette, 479 U.S. 481, 491-94 (1987).

The federal common law cause of action is itself narrow. Once Congress has spoken to a matter, any federal common law that might otherwise exist is “displaced.” And given the separation of powers concerns implicated by this regime, there is a presumption in favor of displacement. Matter of Oswego Barge Corp., 664 F.2d 327, 335 (2d Cir. 1981).

If federal common law is displaced by environmental legislation and state common law does not extend to out-of-state sources, what then of efforts to use state common law to address global issues like climate change? Can a court in one state apply the common law of 49 “source” states and of potentially numerous other foreign jurisdictions to resolve interstate and global issues, or are there structural limits arising from the Constitution that preclude a state common law cause of action for global climate change?

In AEP v. Connecticut, 131 S.Ct. 2527 (2011) —a case finding federal common law for global climate change is displaced —the Court observed that it “remains mindful that it does not have the creative power akin to that vested in Congress.” As to state common law, the Court continued: “Nor have we ever held that a State may sue to abate any and all manner of pollution originating outside its borders.” Id. at 2536.

Federal common law for interstate pollution arose in the early 1900s because state common law did not reach interstate pollution and there was no federal environmental regulation to fill the gap. There is now federal legislation. Under our constitutional system, no state has authority to override that legislation in order to advance its own policies nationally or globally, by enforcing the police powers of another sovereign or by exercising its own police powers as to another sovereign and its citizens. In short, there is no state common law cause of action to regulate or to remedy the impacts of interstate or global climate change.