GreenLatinos v. Suncor Energy (U.S.A.), Inc.
No. 25-1243. 8/3/2026. D.Colo. Judge Federico. Clean Air Act—Diligent Prosecution Bar to Suit—Consent Decree—Administrative Enforcement.
August 3, 2026
More than 20 years ago, the Environmental Protection Agency (EPA) took enforcement action against Valero Energy Corporation and Conoco Phillips under the Clean Air Act (CAA) for refinery emissions. The parties entered into consent decrees that include refinery plants that are now owned and operated by Suncor Energy (U.S.A.), Inc. (Suncor Energy) in Commerce City (the refinery plants). Since entry of the consent decrees, EPA and the Colorado Department of Public Health and Environment (CDPHE) have taken a variety of administrative actions to enforce the consent decrees, including several CDPHE compliance orders and a 2024 joint EPA/CDPHE notice of violation. In 2024, GreenLatinos, Sierra Club, and 350 Colorado (the environmental organizations), on behalf of their members, sued Suncor Energy to enforce the CAA’s mandate. The suit is based on the CAA’s “citizen suit” provision, which allows a person to file a civil action for violation a CAA emission standard or limitation. The operative complaint states 28 claims for relief alleging various violations of the CAA and its implementing regulations and alleges violations of the consent decrees. Suncor Energy moved to dismiss for (1) lack of jurisdiction, arguing that the environmental organizations could not show an injury-in-fact, so they lacked standing; and (2) failure to state a claim upon which relief could be granted under Fed. R. Civ. P. 12(b)(1), arguing that the claims were jurisdictionally barred by 42 USC § 7604(b)(1)(B), which prevents private parties from suing under the CAA if a government entity is “diligently prosecuting” CAA violations as well. The district court concluded the environmental organizations had standing to pursue their claims. It analyzed the Rule 12(b)(1) motion on Rule 12(b)(6) grounds and granted it. The district court then dismissed the environmental organizations’ operative complaint and entered final judgment for Suncor Energy.
As an initial matter on appeal, the Tenth Circuit determined that the district court correctly analyzed the Rule 12(b)(1) motion under Rule 12(b)(6) because the diligent prosecution bar is not jurisdictional. Accordingly, it reviewed the district court’s dismissal de novo.
The environmental organizations argued that the diligent prosecution bar can be triggered only by a civil judicial action that is presently being enforced and that, to preclude the suit, the standard or limitation in the judicial action must be the same as the one in the citizen suit. The Tenth Circuit concluded that the diligent prosecution bar is triggered only by an action in a judicial forum that is presently being enforced. And because a consent decree is a settlement agreement subject to continued judicial oversight, consent decrees in some circumstances may trigger the diligent prosecution bar. In deciding whether the diligent prosecution bar precludes a citizen suit, the CAA requires the court to first identify a present judicial action and ensure that the standards and limitations raised in the potentially preclusive judicial action are the same as the ones in the citizen suit. The district court may consider whether the judicial action is being diligently prosecuted only after these two steps have been satisfied. Here, the district court applied the diligent prosecution bar to standards and limitations that are not in the consent decrees, either because they were in post-consent decree administrative actions or because they were simply similar to the standards or limitations in both the judicial and administrative actions. Both bases for applying the diligent prosecution bar were erroneous.
The judgment was reversed and the case was remanded with directions.