EPA greenhouse gas rules at stake in U.S. Supreme Court

The US Supreme Court is considering an important challenge to the Environmental Protection Agency's (EPA) greenhouse gas (GHG) air permitting rules under the Clean Air Act (CAA). At stake in Utility Air Regulatory Group v EPA (one of six related cases on which the Court granted certiorari) is the validity of EPA's rules for stationary sources of GHG emissions under the Prevention of Significant Deterioration (PSD) provisions of the CAA. The petitions challenged the DC Circuit's unanimous decision upholding the rules in Coalition for Responsible Regulation v EPA, 684 F.3d 102. The Court has now granted review of EPA's determination that regulation of vehicle GHG emissions triggers the application of PSD and Title V permitting programs to stationary sources. The bottom line is that the Supreme Court's decision will be an important next step in defining how far EPA can extend the CAA to regulate GHGs. The decision will by no means, however, be the final word.