On Nov. 25, 2014, the United States Supreme Court granted certiorari to review the United States Court of Appeals for the D.C. Circuit’s April 2014 majority ruling that upheld the utility maximum achievable control technology (MACT) standard, commonly referred to as MATS. The Supreme Court accepted the appeal on one issue, “[w]hether the Environmental Protection Agency unreasonably refused to consider costs in determining whether it is appropriate to regulate hazardous air pollutants emitted by electric utilities.”

In the underlying case, White Stallion Energy Center v. EPA, the D.C. Circuit Court ultimately concluded that EPA’s interpretation of what was “appropriate and necessary” was reasonable and therefore it need not consider cost in determining whether health hazards from electric utility emissions made the utility MACT regulation appropriate and necessary.