Utility Air Regulatory Group et al. v. EPA et al., 134 S. Ct. 2427 (2014).

Thirteen states and a number of industry groups challenged several of the EPA’s actions.  First, the plaintiffs challenged the agency’s “Endangerment Finding,” in which the EPA determined that greenhouse gases may “reasonably be anticipated to endanger public health or welfare.”  Second, the plaintiffs challenged EPA’s “Tailpipe Rule,” which sets emission standards for certain classes of motor vehicles.  Third, the plaintiffs challenged EPA’s “Timing and Tailoring Rules,” which regulated greenhouse gas emissions from stationary sources such as power plants and refineries pursuant to Title V of the Act.  Soon after the case was filed with the D.C. Circuit, fifteen states moved to intervene in support of the EPA.

The Supreme Court, drawing on Massachusetts v. EPA, upheld the agency’s “Endangerment Finding,” and the “Tailpipe Rule.”  However, it warned that the agency cannot apply the broad definition for “air pollutant” as was the case in Massachusetts to all provisions of the Clean Air Act, particularly with respect to regulation of stationary sources under Title V since the agency itself has routinely given it a narrower meaning.  The Court then stated that the agency must limit its approach under the “Timing and Tailoring Rules” to facilities that are already required to obtain permits.