The Tenth Circuit Court of Appeals has affirmed the dismissal of a Clean Air Act citizen suit based on the doctrine of issue preclusion. Sierra Club v. Two Elk Generation Partners, No. 10-8032 (10th Cir. 5/31/11). Plaintiff filed the suit to block the construction of a coal-fired power plant in Campbell County, Wyoming. The Wyoming Department of Environmental Quality (DEQ) had determined the validity of the facility’s permits during hearings before the DEQ Council in 2005 and 2007. Rejecting plaintiff’s challenge, a state district court upheld those decisions in March 2009. Before plaintiff voluntarily dismissed its appeal of the state court ruling, it challenged the permits in federal court. According to both the federal district and appellate courts, “[T]he doctrine of issue preclusion declares that parties may not relitigate matters that have already been decided if the issues are identical and the standards of due process have been met.”