[JURIST] The US Supreme Court [official website] on Monday limited the power of the Environmental Protection Agency (EPA) [official website] to regulate greenhouse gases while still leaving the agency free to do so in most cases. In Utility Air Regulatory Group v. EPA [SCOTUSblog backgrounder], which was consolidated with six other cases, the court was considering whether the EPA permissibly determined that its regulation of greenhouse gas emissions from new motor vehicles triggered permitting requirements under the Clean Air Act [text, PDF] for stationary sources that emit greenhouse gases. Stationary sources are typically electricity-generating utility plants and major factories, and the permitting requirements in question involve the EPA’s authority under the Clean Air Act’s Title I and Title V [text] to issue permits for construction or modification and operation of stationary sources. A three-judge panel for the US Court of Appeals for the District of Columbia Circuit upheld [opinion] the EPA’s determination that greenhouse gases were an endangering pollutant that the EPA was obliged to regulate. A divided court affirmed in part and reversed in part, with the majority opinion written by Justice Antonin Scalia:

To sum up: We hold that EPA exceeded its statutory authority when it interpreted the Clean Air Act to require [prevention of significant deterioration (PSD)] and Title V permitting for stationary sources based on their greenhouse-gas emissions. Specifically, the Agency may not treat greenhouse gases as a pollutant for purposes of defining a “major emitting facility” (or a “modification” thereof) in the PSD context or a “major source” in the Title V context. To the extent its regulations purport to do so, they are invalid. EPA may, however, continue to treat greenhouse gases as a “pollutant subject to regulation under this chapter” for purposes of requiring [best available control technology] for “anyway” sources.

Chief Justice John Roberts and Justice Anthony Kennedy joined Scalia’s opinion in full. Justice Stephen Breyer filed an opinion concurring in part and dissenting in part, joined by Justices Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan. They would have given the EPA broader authority to regulate emissions. Justice Samuel Alito also filed an opinion concurring in part and dissenting in part, joined by Justice Clarence Thomas.

The court heard arguments in the case in February after granting certiorari [JURIST reports] in October. Monday’s decision follows a 2007 ruling in Massachusetts v. EPA [JURIST report] in which the court found that the EPA has authority to regulate greenhouse gas emissions from automobiles.