On May 31, the U.S. Court of Appeals for the Tenth Circuit upheld a lower court’s dismissal of a lawsuit filed by the Sierra Club against a power generator in Wyoming, saying the conservation group’s legal action was barred by the doctrine of issue preclusion. The Sierra Club originally filed its case in January 2009 under the citizen suit provision of the Clean Air Act against Two Elk Generation Partners, which is attempting the build a coal-fired power plant in the state.