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On Wednesday, the U.S. Court of Appeals for the District of Columbia Circuit denied EPA’s request to partially vacate portions of its 2024 PFAS drinking water rule in American Water Works Association, et al. v. U.S. Environmental Protection Agency, No. 24-1188. In a short per curiam order, a unanimous three-judge panel (Judges Millett, Pan, and Garcia) concluded that “the merits of the parties’ positions are not so clear as to warrant summary action,” and refused to unwind the rule while the case proceeds on the merits. The decision keeps the Biden-era standards fully in place—for now.

The case arises from EPA’s first-ever National Primary Drinking Water Regulation (NPDWR) establishing enforceable limits for six PFAS compounds under the Safe Drinking Water Act. Water sector petitioners, including the American Water Works Association and the Association of Metropolitan Water Agencies, challenged the rule as technically flawed and procedurally defective. After the change in administration, EPA took the unusual step of moving the court to partially vacate the rule for four PFAS compounds (but seeking to keep in place the limits for PFOA and PFOS), effectively seeking to undo parts of its own regulation mid-litigation. A collection of intervenors – composed of the Natural Resources Defense Council and other advocacy groups – opposed EPA’s motion.

The D.C. Circuit was not persuaded that such relief was appropriate at this early stage and denied the motion to vacate. The court also denied several related procedural motions, including requests for expanded intervenor briefing, signaling an intent to keep the case on a relatively disciplined track as it moves forward.

Importantly, the order does not resolve the legality of the PFAS standards themselves. Instead, it preserves the regulatory status quo while the court considers full briefing on the merits. That posture is consistent with recent D.C. Circuit precedent—most notably NRDC v. Regan—that limits EPA’s ability to walk back final Safe Drinking Water Act determinations once they have been made. In that context, the court’s refusal to grant partial vacatur may reflect skepticism toward efforts to achieve through litigation what the statute may not permit through administrative reversal.

What comes next is a compressed merits schedule. Petitioners’ reply briefs are due February 20, 2026, followed by final briefs on March 6, 2026, at which point EPA must also identify any arguments it no longer advances in defense of the rule. The case will then be teed up for argument and a decision that could have lasting implications not only for PFAS regulation, but for how far an administration can go in retreating from its predecessor’s environmental rules once statutory obligations have been triggered.

For further questions regarding this case and other PFAS issues, contact Liskow attorneys Michael Mims, Emily von Qualen, and visit our pages for our Environmental and Toxic Tort practices.