The three-judge panel unanimously agreed to reject the petition, upholding EPA’s broad discretion, supported by case law, to “exercise reasonable discretion in determining when to add a new source to the list of regulated air pollutants.” That discretion, said the court, includes “discretion to prioritize sources that are the most significant threats to public health.”

The EPA, in its defense, did not foreclose the possibility that it will include coal mine methane among regulated emissions in the future. The court, however, rejected WEG’s contention that the EPA could not delay the rulemaking despite the good reasons it may have for doing so as “contrary to precedent.”