The But-For Causation Split and the Certification Backdoor: Defending AKS-Tainted False Claims

The False Claims Act is the federal government's most powerful civil fraud tool, and in the healthcare sector its most common predicate is the Anti-Kickback Statute. Roughly three-quarters of FCA settlements arise from healthcare matters, and a large share of those rest on the theory that an illegal kickback tainted the claims a provider later submitted for federal reimbursement. The question that determines the reach of that theory is deceptively simple: how tight must the causal link be between the kickback and the claim?

A growing majority of the federal circuits now answers that the kickback must be the but-for cause of the claim, a standard that imposes a real evidentiary burden on the government and relators. The most recent and most thorough decision, the First Circuit's opinion in United States v. Regeneron Pharmaceuticals, Inc., deepened the split and handed defendants a significant tool. But the same opinion preserved a separate pathway to liability that requires no causation showing at all. A defense built only on the causation victory, without accounting for that second track, is incomplete. This paper explains the split, the decisive nuance, and how to defend on both fronts.

The 2010 Amendment and the Causation Question

The Anti-Kickback Statute is a criminal statute that prohibits offering or paying remuneration to induce referrals of items or services payable by federal healthcare programs. Standing alone, it creates no civil liability. The bridge to the False Claims Act was built by a 2010 amendment, which provides that a claim that includes items or services resulting from an AKS violation constitutes a false or fraudulent claim for purposes of the FCA.

The entire dispute turns on two words. Does a claim result from a kickback whenever the claim follows the kickback in some causal chain, or only when the claim would not have been submitted but for the kickback? The difference is enormous. Under the looser reading, proof that a provider received remuneration and later submitted claims can suffice. Under the stricter reading, the government must prove that the specific claim would not exist absent the kickback, which in many cases means proving why a physician made a particular treatment decision.

A Three-to-One Circuit Split

The circuits have divided, and the division is now three to one in favor of the stricter standard.

The but-for majority. The Eighth Circuit was first, holding in United States ex rel. Cairns v. D.S. Medical LLC, 42 F.4th 828 (8th Cir. 2022), that the 2010 amendment's 'resulting from' language requires but-for causation. The Sixth Circuit followed in United States ex rel. Martin v. Hathaway, 63 F.4th 1043 (6th Cir. 2023), reaching the same conclusion. The Supreme Court declined to review the Sixth Circuit's decision in 2023, leaving the standard in place.

The First Circuit joins. In United States v. Regeneron Pharmaceuticals, Inc., 2025 WL 520466 (1st Cir. Feb. 18, 2025), a unanimous panel, in an opinion by Judge Kayatta, affirmed Chief Judge Saylor's ruling below and adopted but-for causation. The court reasoned that the phrase 'resulting from' carries an ordinary meaning of but-for causation, a default the Supreme Court has described as a background principle against which Congress legislates, and that nothing in the text of the 2010 amendment displaced that default. The court declined to read the FCA's civil causation requirement as tracking the AKS's criminal provisions, which require no such proof, observing that the criminal and civil provisions serve different purposes.

The Third Circuit holdout. The Third Circuit stands alone on the other side, having held, relying heavily on legislative history, that the government need prove only some connection or link between the kickback and the subsequent claim, treating the kickback as actionable if it was merely a contributing factor. In the Third Circuit, then, the same conduct that would fail for lack of but-for causation elsewhere can still support liability.

The facts of Regeneron illustrate how demanding the but-for standard can be for the government. The allegation was that Regeneron donated more than sixty million dollars to a charitable foundation that covered patient copayments for an eye drug used to treat age-related macular degeneration, thereby inducing prescriptions that generated Medicare claims. The government could not show that any particular claim would not have been submitted absent the donations, conceding the difficulty of proving why a physician prescribed a given drug. Under the but-for standard, that gap was fatal to the theory.

The Certification Backdoor

Here is the nuance that a defendant must not overlook, and that makes the causation victory partial rather than complete. The Regeneron court was explicit that the 2010 amendment is not the only route from an AKS violation to FCA liability. The implied false-certification theory is a separate pathway, and the court stated that claims under the 2010 amendment run on a separate track than do claims under a false-certification theory.

The significance is that the false-certification track requires no proof of but-for causation. Under that theory, FCA liability attaches where compliance with the AKS is a precondition of payment and a provider falsely certifies compliance when submitting a claim. The falsity inheres in the certification itself, not in the causal relationship between the kickback and the particular claim. The Regeneron court suggested that false-certification claims require no proof of causation at all.

Put simply, claims under the 2010 amendment run on a separate track than do claims under a false-certification theory.

— United States v. Regeneron Pharmaceuticals, Inc., 2025 WL 520466 (1st Cir. 2025)

This pathway is broadly available because of how healthcare claims are submitted. Virtually every claim form used to bill federal healthcare programs carries a certification of compliance with applicable law, including the AKS. That structural feature means the government and relators can often plead a false-certification theory in the same cases where but-for causation would be hard to prove, recapturing through certification what the causation standard would otherwise foreclose. The government has signaled that where the causation track is difficult, it may pursue the certification track instead, and recent enforcement reflects continued success under false-certification theories.

Defending on Both Tracks

Because the government can proceed on either the 2010-amendment track or the certification track, a complete defense addresses both. The following framework reflects that dual posture.

Press the causation standard where it governs. In the First, Sixth, and Eighth Circuits, and in district courts persuaded by their reasoning, the but-for requirement is a powerful summary-judgment tool. The defense should hold the government to proof that the specific claims would not have been submitted absent the alleged kickback, exploiting the difficulty of proving why individual treatment decisions were made. The follow-on First Circuit authority confirms the standard's force: courts in that circuit have affirmed dismissals where relators failed to plead that particular referrals would not have occurred but for the alleged kickbacks.

Contest the certification theory on its own elements. Where the government pleads false certification to avoid the causation requirement, the defense shifts to that theory's elements: whether AKS compliance was genuinely a precondition of payment, whether any certification was actually false, and whether the materiality and scienter requirements that govern all FCA claims are met. The certification track avoids causation, but it does not avoid materiality or knowledge, and those remain contestable.

Preserve the split for appellate review. Because the causation question is unsettled and may reach the Supreme Court, the standard-of-causation argument should be raised and preserved at every stage, particularly in circuits that have not yet ruled. Our appellate practice works with trial teams to frame and preserve the 'resulting from' question, so that a defendant is positioned to benefit from the favorable majority position and from any eventual Supreme Court resolution.

Build the factual record early. Both tracks are won or lost on facts: on the causation track, the independent clinical reasons for treatment decisions; on the certification track, the precise content and role of the certifications at issue. Our internal investigations teams develop the factual record on the legitimate, independent bases for the conduct at issue, and our discovery strategy and management teams ensure that the evidence bearing on causation and certification is identified and preserved before positions harden.

Conclusion

The causation split is a genuine and growing advantage for healthcare defendants. Three circuits now require the government to prove that an AKS-tainted claim would not have been submitted but for the kickback, a burden that Regeneron itself shows can be decisive, and the Supreme Court may ultimately make that standard uniform. But the victory is partial by the express terms of the decision that delivered it. The implied false-certification theory remains a separate track that requires no causation showing and is broadly available because of how healthcare claims are certified. The defendants best positioned are those who understand both tracks: pressing the but-for standard where it governs, contesting the certification theory on materiality and scienter where the government retreats to it, preserving the causation question for the appellate review that is surely coming, and building early the factual record that both defenses require. The causation split changed the terrain, but it did not end the contest.