On September 15, 2006, WLF filed a brief with the Supreme Court urging it to reject an attempt by several environmental groups and the EPA to overturn a court of appeals ruling in a Clean Air Act case in favor of Duke Energy Corporation. The court rejected EPA’s flawed interpretation of its 1980 Prevention of Significant Deterioration Rule that power companies are required to obtain costly permits for modifications of their power plants even if the net result is less emissions. WLF also argued that, contrary to EPA’s contention, the Fourth Circuit had jurisdiction to adjudicate Duke Energy’s valid defense to the enforcement action brought by the EPA because Duke Energy was not challenging the 1980 PSD Rule itself, but EPA’s unlawful interpretation of the rule. Under the Act, judicial review of final EPA rules and agency actions can be heard only in the D.C. Circuit.