Supreme Court Reverses D.C. Circuit Decision on MATS Rule

On June 29, 2015, in the consolidated case of Michigan v. EPA, the U.S. Supreme Court held that EPA interpreted §7412(n)(1)(A) of the Clean Air Act unreasonably when it deemed cost irrelevant to the decision to regulate hazardous air pollutant (HAP) emissions from power plants. Thus the Court reverses the judgment of the D.C. Circuit and remands the cases for further proceedings consistent with this opinion. This issue brief summarizes the decision, written by Justice Scalia which was joined by Chief Justice Roberts and Justices Kennedy, Thomas and Alito, as well as the dissent written by Justice Kagan joined by Justices Ginsberg, Breyer, and Sotomayor.