The United States Supreme Court plays a unique and important role in resolving environmental controversies that arise among the several states states and in enforcing environmental compacts formed by states with the assent of Congress.

The powers of Congress and the states to unilaterally resolve environmental controversies between states are constitutionally limited. But there are two plenary constitutional mechanisms for resolving environmental controversies among the states: (1) litigation under the original jurisdiction of the Supreme Court over controversies between two or more states; and (2) negotiation of compacts between states with Congressional assent that are enforceable against states by Acts of Congress and by states through suits filed in the Supreme Court.

The Supreme Court’s resolution of environmental controversies and enforcement of environmental compacts falls into two categories. First, the Court apportions natural resources among states through federal common law suits and by enforcing resource apportionment compacts. Second, the Court protects state natural resources from inequitable disruption by other states through federal common law suits and by enforcing resource protection compacts. The Court has to date asserted its jurisdiction to apportion territory, water, and fish and to protect navigation, land use, and water. The Court has not yet asserted its jurisdiction to protect air from pollution, but this Article argues that air pollution suits are open to downwind states because the Clean Air Act only displaces actions against emissions from individual sources, not entire states.