Several States, a city, and land trusts filed federal common law public nuisance claims against various power companies; they requested that the court set CO2 emission limits.
In American Electric Power Co. et al v. Connecticut et al, 2011 U.S. LEXIS 4565 (6/20/11), the U.S. Supreme Court addressed the issue. The Court found that Clean Air Act (CAA) and the EPA actions authorized by the CAA displaced any federal common law right to seek the relief sought, especially given that the CAA "spoke directly" to such emissions. 42 U.S.C. Section 7411. Section 7411 directed the EPA to list categories of air pollution and establish emission standards. GHG emisisons were air pollutants within the meaning of 42 U.S.C. Section 7602(g). If EPA fails to set appropriate standards, the CAA provides a mechanism for petitioning EPA to set such standards.
The Court also noted that EPA was doing so for greenhouse gas emissions from fossil-fuel fired power plants. Further, the CAA provides a means to seek limits on the emissions, which is the same relief the plaintiffs sought by invoking federal common law. Further, the CAA allows for trade-offs and for a sophisticated differentiation between sources, impacts, etc. Because Congress has delegated to EPA the decision whether and how to regulate carbon-dioxide emissions from power plants, the delegation displaced federal common law. As such, there was a conflict between what plaintiffs sought in terms of relief from the judicial system and the statutory scheme Congress enacted.
The Court found that it was error for the 2nd Circuit to find that federal judges could set limits on greenhouse gas emissions in face of a law empowering the EPA to set the same limits, subject to judicial review only to ensure against arbitrary, capricious, or unlawful action under 42 U.S.C. Section 7607(d)(9).