Boundaries matter.

Several Louisiana parishes sought damages under a state statute for damages arising from the Deepwater Horizon incident.  In re Deepwater Horizon, No. 12-30012 (Feb. 24, 2014).  Condensing a much more nuanced opinion — the Fifth Circuit held that the claims were preempted by the Clean Water Act under International Paper v. Oulette, 479 U.S. 481 (1987), because the pollution arose from a source outside Louisiana.  The Court rejected arguments that the Oil Pollution Act of 1990 (prompted by the Valdez disaster) changed that analysis, and concluded that the Supreme Court ruled consistently with this result in Arkansas v. Oklahoma, 503 U.S. 91 (1992).