On June 20, 2011, the U.S. Supreme Court unanimously held that the Clean Air Act displaces federal suits alleging that emitting carbon dioxide constitutes a public nuisance under federal common law. In doing so, the Court rejected a lawsuit brought by plaintiffs, including eight States and New York City, against American Electric Power Co. and five other leading utility companies who own and operate power plants in twenty States. The decision was a victory for WLF, which filed a brief in the case urging the Court to reject the plaintiffs’ attempt to force the defendants to cap and reduce their carbon dioxide emissions. While the Court’s holding reached only the plaintiffs’ federal common law claims, the ruling should give federal courts pause before allowing any similar state law claims to proceed.