In a split decision, the U. S. Supreme Court ruled on Monday June 23rd that the U.S. Environmental Protection Agency (“EPA”) does not have authority under the federal Clean Air Act to require major source permits based solely on emissions of greenhouse gases. Specifically, the Court said that the agency may not treat greenhouse gases as a pollutant for purposes of defining a “major emitting facility” (or a “modification” thereof) in the context of prevention of significant deterioration (“PSD”) permits for major sources of emissions or for purposes of defining a “major source” in the operating permit (Title V) context. The Court ruled, however, that EPA may continue to treat greenhouse gases as a “pollutant subject to regulation under this chapter” for purposes of requiring BACT for so-called “anyway” sources (i.e., sources that are subject to PSD permitting due to their emissions of other pollutants). Justice Scalia wrote the opinion for the Court. There were a number of concurring and dissenting opinions as to various parts.