On June 30, 2025, the Supreme Court denied industry group petitions to review and reverse two cases—one out of the Fifth Circuit and the other out of the Ninth Circuit—that could have significantly restricted the ability of citizens to sue over environmental violations. The Courts of Appeals held that citizens have broad powers to bring lawsuits to enforce the Clean Air Act (CAA) and the Clean Water Act (CWA). As a result, environmental citizen suits will continue to play an important role in enforcing compliance with environmental laws. The denials have added significance because environmental groups have indicated that they intend to more aggressively bring citizen suit claims as the Environmental Protection Agency shifts its enforcement priorities.
The CWA and CAA both include citizen suit provisions that allow individuals and organizations to sue regulated entities who violate environmental standards. These provisions empower citizens to enforce the law when federal or state regulators have not done so, serving as a backstop to government enforcement. Plaintiffs in citizen suits have access to multiple remedies, including injunctive relief and monetary penalties paid to the U.S. Treasury. The inflation-adjusted maximum civil penalties per day for each violation under the CAA and CWA are $124,426 and $68,445, respectively.
In the Fifth Circuit, the Court of Appeals upheld a multimillion-dollar penalty for various CAA violations. The litigation spanned nearly a decade and involved multiple appeals to the Fifth Circuit, which ultimately affirmed without opinion the district court’s holding that the plaintiffs had satisfied Article III’s standing requirements.
Industry petitioners urged the Supreme Court to take the case and reverse the civil penalty for two reasons. Most broadly, industry petitioners urged the Court to revisit its 2000 decision in Friends of the Earth v. Laidlaw, which held that civil penalties paid to the government, rather than to the plaintiffs themselves, can satisfy Article III’s redressability requirement. Petitioners’ argument would have limited citizen-plaintiffs to injunctive relief. Petitioners also argued that the Court should dramatically narrow the scope of violations for which citizen-plaintiffs may recover civil penalties to include only those violations that the plaintiffs had established directly injured them. A group of twenty-seven states, including Idaho, Utah, Wyoming, Montana, and Texas, supported the petition for certiorari. The states warned that the ruling could risk opening the floodgates to citizen suits and usurp the role of government regulators.
In the Ninth Circuit, the Court of Appeals held that environmental groups may enforce state-issued CWA permits in federal court under the CWA’s citizen suit provision, even the parts of those permits containing requirements more stringent than federal standards. The U.S. Solicitor General had urged the Supreme Court to take the case, citing a direct conflict with the Second Circuit’s 1993 decision in Atlantic States Legal Foundation, Inc. v. Eastman Kodak Co., which held that the CWA does not authorize citizens to enforce provisions of state-issued permits that are based on state law and have greater scopes of coverage than CWA requirements. The Ninth Circuit recognized a potential conflict with Atlantic States, but noted that the decision directly conflicted with Ninth Circuit precedent that it was bound to follow.
With the Supreme Court declining to take up either case, the current, broad scope of citizen suit authority remains intact. As a result, citizen suits will likely continue to play an important role in environmental enforcement, especially amid a shift in the federal enforcement landscape. Furthermore, the Ninth Circuit decision holds open the possibility that enforcement of state permit conditions could be more broadly applied to federal citizen suits in other contexts outside the CWA.
In summary, the broad citizen suit enforcement powers currently recognized in the Courts of Appeals highlight the continued importance of compliance with environmental law for all regulated entities.
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