Anti-Kickback Statute Premised False Claims Cases: The “But For” Causation Standard Finds Support from First Circuit

It’s now 3–1, with the First Circuit (2025) aligning with the Sixth (2023) and Eighth (2022) Circuits finding the meaning of the words “resulting from” — as used in a 2010 amendment to the federal Anti-Kickback Statute (AKS) — to require “but for” causation in AKS-premised False Claims Act (FCA) cases. This is the third time a circuit court has diverged from the 2018 Third Circuit decision, which held that the phrase “resulting from” requires the government (or relator) to prove only a link “between the alleged kickbacks and the medical care received. . . .”

Notably, in October 2023, the Supreme Court declined to review the Sixth Circuit Court of Appeals case. As such, the circuit split on causation continues — and all parties should be aware of the applicable case law where they reside.

Background

In 2010, Congress amended the AKS to provide that any Medicare claim “that includes items or services resulting from a violation of [the AKS] constitutes a false or fraudulent claim for purposes of [the FCA].” Fifteen years later, the courts are still working through what this amendment means for FCA cases.

In the First Circuit case, United States v. Regeneron Pharmaceuticals, Inc., the complaint alleged Regeneron’s efforts to funnel money into Chronic Disease Fund — an independent charitable foundation — specifically to reimburse patients’ copays from one of Regeneron’s products, Eylea, violated the AKS, and the resulting claims to Medicare were allegedly tainted by these illegal kickbacks in violation of the FCA.

This case was before Chief Judge Saylor in the District of Massachusetts. Three months after a different District of Massachusetts court judge found “but for” causation is not the causation standard in AKS-premised FCA cases, Chief Judge Saylor wrote the opinion in Regeneron, finding the “but for” standard applicable in AKS-premised FCA cases and denied the government’s motion for summary judgment. Chief Judge Saylor explicitly called out that the Third Circuit case was not binding and that the “only a link” standard “is divorced from the actual language of the statute and from basic principles of statutory interpretation.” The case was then appealed to the First Circuit.

On July 22, 2024, the First Circuit heard oral argument on what the appropriate standard of causation is for AKS-premised FCA claims. The specific issue on appeal was whether a “claim” under the FCA “result[s] from” a kickback only if the claim would not have included the items or services but for the kickback. On February 18, 2025, the First Circuit released its opinion in United States v. Regeneron Pharma., Inc., finding against the government in holding an AKS violation must be a “but for” cause of the challenged claim.

But-For Causation in Regeneron

There is a default assumption derived from the Supreme Court that “resulting from” is read as calling for a but-for causation standard “in the usual course.” While this is not an immutable rule, there needs to be support for any deviation to the typical reading.

Regeneron argued that a but-for causation standard was appropriate, and there is no reason to deviate from the standard reading. Specifically, Regeneron argued that under the 2010 AKS amendment, the government bears the burden of proving an AKS violation actually caused a provider to provide different medical treatment (and thus caused the false claim). That is, the claim would not have been submitted but for the alleged kickback.

Meanwhile, the government argued that this is exactly this situation where the usual does not apply with three points:

The AKS itself requires no proof that the government would not have paid a claim but for the inducement of the offered kickback.
Congress did not intend to alter false-certification case law by imposing a but-for causation requirement in the 2010 AKS amendment.
Legislative history for the 2010 AKS amendment supports something other than the but-for causation.

None of these arguments were persuasive to the First Circuit, which found “no convincing ‘textual or contextual’ reason to deviate from the default presumption that the phrase ‘resulting from’ as used in the 2010 amendment imposes a but for causation standard.” As a result, the First Circuit held the government must show that an illicit kickback was the but-for cause of a submitted claim.

Looking Ahead

While the spoken Circuit Courts are generally finding in favor of “but for” causation for AKS-premised FCA cases, several circuit courts have yet to weigh in, and there is a split with the Third Circuit. Unless and until the Supreme Court grants certiorari on a causation case, we will continue to see differences on how courts approach these issues within district courts without controlling case law. Government attorneys and the relators’ bar may continue to try out different theories, hoping a court may find them persuasive, which could result in splits between district courts and a deeper divide at the circuit courts.

Observers and impacted parties will want to watch the developing case law in this area to see how courts square with this circuit split.

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