On August 23, 2019, the U.S. Court of Appeals for the District of Columbia Circuit (DC Circuit) issued a decision in Murray Energy Corp. v. EPA, in which various states, industry and environmental groups had challenged EPA's 2015 ozone primary and secondary NAAQS and various implementation details. The DC Circuit upheld EPA's primary NAAQS, remanded the secondary NAAQS and vacated EPA's decision to "grandfather" in-process PSD permits from the need to comply with a newly-promulgated NAAQS. From an NSR standpoint, Murray Energy may represent the end of grandfathering.
