In May, 2014, Group Against Smog and Pollution (GASP) sued coke producer Shenango, Inc. under the Clean Air Act’s (CAA) citizen suit provision for allegedly violating opacity limits in its air permit for its Neville Island, Pennsylvania facility. Prior to that lawsuit, U.S. EPA, Pennsylvania Department of Environmental Protection (DEP) and Allegheny County Health Department (ACHD) had sued Shenango in 2012 in the U.S. District Court for the Western District of Pennsylvania and entered into a consent decree addressing opacity violations. The Court retained jurisdiction to enforce the consent decree. In 2014, ACHD sued Shenango in the Allegheny County Court of Common Pleas for opacity violations, resulting in a consent order reaffirming the 2012 consent decree and addressing further claims of violations. Because of those legal actions by federal, state and county regulators, a three-judge panel of the U.S. Court of Appeals for the Third Circuit on January 6 unanimously ruled that the enforcement action by the regulatory agencies barred the lawsuit by GASP regardless of whether the enforcement action was still pending. The court’s opinion categorized the diligent prosecution bar under the CAA as a “claim-processing rule, not a jurisdictional limitation.” Where there is or has been diligent prosecution by federal or state governments against the alleged violator that is applicable to the violations alleged in the citizen suit, the citizen suit fails to state a claim upon which relief can be granted, and therefore must be dismissed. Because ACHD prosecuted the same three CAA violations alleged by GASP, and the consent order from that prosecution was still in effect, the Third Circuit ruled the GASP claim must be dismissed. Group Against Smog and Pollution (GASP) v. Shenango, Inc. (No. 15-2041, 3rd Cir., January 6, 2016). “When a state or federal agency diligently prosecutes an underlying action in court, the diligent prosecution bar will prohibit citizen suits during the actual litigation as well as after the litigation has been terminated by a final judgment, consent decree, or consent order and agreement.” The Third Circuit’s ruling is in agreement with similar rulings by the 1st, 4th, 7th and 10th Circuits.