5. In AMERICAN ELEC. POWER CO., INC. v. CONNECTICUT, 131 S.Ct. 2527, 180 L.Ed.2d 435 (2011), the Court addressed whether plaintiffs, which included several States, New York City, and three private land trusts, could bring federal common law nuisance claims against four private power companies and the federal Tennessee Valley Authority for their emission of carbon dioxide. Plaintiffs sought an order setting emissions caps for each defendant. The Court acknowledged that environmental protection is within the national power and one in which the federal courts may devise federal rules490of decision. However, the Court held that federal judicial power had been displaced by Congress in the Clean Air Act and the establishment of the Environmental Protection Agency (EPA). The Court rejected the argument that “federal common law is not displaced until EPA actually exercises its regulatory authority, i.e., until it sets standards governing emissions from the defendants’

plants.” Id. at 2538, 180 L.Ed.2d at 448. In her opinion for the Court, Justice Ginsburg explained:

* * * [T]he relevant question for purposes of displacement is “whether the field has been occupied, not whether it has been occupied in a particular manner.” * * *