The U.S. Supreme Court last month held that the Clean Air Act ("CAA") displaces federal common law claims designed to stop injuries allegedly resulting from greenhouse gases emitted by fossil-fuel fired power plants. Justice Ginsburg authored the Court's opinion in American Electric Power Co. v. Connecticut, No. 10-174 (2011). The Court began by reviewing its earlier decision in Massachusetts v. EPA, 549 U.S. 497 (2007), wherein the Court held that the CAA authorized the U.S. Environmental Protection Agency ("EPA") to regulate emissions of carbon dioxide and other greenhouse gases. On the merits, citing earlier decisions on common law interstate pollution claims, the Court stressed that the relevant question is whether the CAA "speak[s] directly to [the] question" at issue. Since the Court's decision in Massachusetts held greenhouse gases "qualify as 'air pollutant[s]'" subject to regulation under the CAA , that statute "speaks directly" to emissions of carbon dioxide from the defendants' power plants. If EPA fails to set emission limits acceptable to the plaintiffs, then their appropriate course is to petition EPA to do so and seek review of EPA's final action in federal courts. The Court concluded: "The [CAA] itself thus provides a means to seek limits on emissions of carbon dioxide from domestic power plants – the same relief the plaintiffs seek by invoking federal common law. We see no room for a parallel track." The Court found it was of no moment that EPA had not yet actually exercised its authority to regulate greenhouse gases. Rather, the "critical point" was that Congress delegated to EPA the authority to decide how such regulation should be conducted and "the delegation is what displaces federal common law."