Photo Credit: Fed. Bureau of Investigation, White Collar Crime: Health Care Fraud, https://www.fbi.gov/investigate/white-collar-crime/health-care-fraud (last visited Sep. 10, 2025).
Authored by: Sarah K. Conway
On February 18, 2025, the First Circuit joined two of its sister circuits in ruling that the 2010 amendment to the Affordable Care Act (“ACA”) imposed a “but-for” causation standard for determining whether a violation of the Anti-Kickback Statute may also create liability under the False Claims Act.[1] The Anti-Kickback Statute (“AKS”) makes it a crime to knowingly and willfully solicit or receive “any remuneration (including any kickback, bribe, or rebate) directly or indirectly, overtly or covertly, in cash or in kind” in exchange for payment made under a federal health care program.[2] Conversely, the False Claims Act (“FCA”) is a civil statute that imposes liability for knowingly presenting false or fraudulent claims to the federal government for payment or approval.[3]
Although distinct, these health care fraud and abuse laws are often interwoven. The most prominent example of this link is inscribed in the 2010 amendment to the ACA, which allows criminal violations under the AKS to form the basis of civil liability under the FCA.[4] The amendment specifically states that a claim “that includes items or services resulting from a violation” of the AKS will constitute a false or fraudulent claim sufficient to also impose liability under the FCA.[5] Recently, this “resulting from” language within the amendment has become the center of an ongoing circuit split that asks whether the language was intended to impose a “but-for” causation requirement or some lesser causation standard.[6]
The differences in these standards can be vast. For instance, a but-for causation standard requires the plaintiff to prove that, without the defendant’s action, they would not have sustained the alleged injuries.[7] Compare this standard with a “causal link” standard which merely requires some recognizable link between “the alleged kickbacks and the medical care received by at least one of [the defendant’s] federally insured patients.”[8] Defining the precise causation standard is crucial as it impacts the evidentiary burden for plaintiffs along with the breadth of potential liability for defendants.[9]
This burden of proof analysis took center stage in the First Circuit case of United States v. Regeneron Pharmaceuticals.[10] At issue in this case is an alleged violation of the AKS that stems from Regeneron’s prescriptions of a costly drug used to treat neovascular age-related macular degeneration.[11] This drug, called Eylea, is administered in office via an injection that costs $1,850 per patient, per dose.[12] As the First Circuit notes, “Medicare Part B has spent over $11.5 billion on Eylea,” making the drug an economic powerhouse for manufacturers like Regeneron.[13] According to the government, Regeneron developed a rebate scheme to induce Medicare Part B beneficiaries to purchase Eylea by refunding any co-pays associated with the prescription.[14] The alleged refunds were not made directly to beneficiaries.[15] Rather, they took the form of donations to a charity that provides financial assistance to those suffering with the same disease Eylea is designed to treat.[16] While genuine donations to charitable foundations are permitted under federal law, the Department of Health and Human Services (“HHS”) has warned about the fine line between donations and so-called “rebate conduits,” such as the one Regeneron allegedly developed.[17]
At trial, the government argued that Regeneron’s AKS rebate scheme was sufficient to form the basis of an FCA claim because the words “resulting from” in the 2010 amendment merely require a causal link between patient exposure to the rebate scheme and provider claims for reimbursement.[18] The government’s adoption of this lesser causation standard aligned with that of the Third Circuit, which held that but-for causation was “too exacting” of a standard.[19] Contrarily, Regeneron argued that actual influence or causation, also termed but-for causation, must exist to link a violation of the AKS to an FCA claim.[20] Regeneron’s position aligned with that of the Sixth and Eighth Circuits, which both interpreted the phrase “resulting from” to indicate a but-for causation requirement.[21]
Upon review, the First Circuit sided with Regeneron’s interpretation—and by extension the Sixth and Eighth Circuits—and ruled that the “resulting from” language imposed a “requirement of actual causality, which in [the] ordinary course takes the form of but-for causation.”[22] The First Circuit emphasized that the Supreme Court has regularly held the phrase “resulting from” to constitute a but-for causation requirement absent textual indication to the contrary.[23] Despite this, the government continued to argue that imposition of a but-for causation requirement would upend the false certification theory of FCA liability.[24] While the First Circuit agreed that there had been no change to false certification case law which would impose a but-for causation requirement, it clarified that liability under the false certification theory is distinct from liability brought under the 2010 amendment.[25] In other terms, the 2010 amendment offers an alternative pathway for establishing a violation of the FCA that does not require the same elements as the false certification theory.[26]
Other circuits have held similarly to the First.[27] For example, in 2024, the Seventh Circuit interpreted the phrase “resulting from” to require a causal nexus between a defendant’s violation of the FCA and their involvement with an illegal kickback scheme.[28] Although the Supreme Court has yet to weigh-in on the issue, the ongoing circuit split seems to be gaining enough traction to place it on the Court’s radar. The resolution of the split is likely to have monumental repercussions for health care attorneys. If the Supreme Court were to side with the majority and impose a but-for causation requirement, there will be an increased burden on whistleblowers and the government to present evidence of a genuine connection between an AKS violation and the associated false claims.[29] This heightened causation requirement would also provide defense teams with another avenue to combat AKS based FCA claims, ultimately tipping the burden of proof scale for such health care fraud cases in favor of defendants.[30]
[1] United States v. Regeneron Pharms., Inc., 128 F.4th 324, 336 (1st Cir. 2025).
[2] 42 U.S.C. § 1320a-7b(b).
[3] 31 U.S.C. § 3729(a)(1).
[4] Patient Protection & Affordable Care Act, Pub. L. No. 111-148, § 6402(f)(1), 124 Stat. 119, 759 (2010) (codified as amendment at 42 U.S.C. § 1320a-7b(g)).
[5] 42 U.S.C. § 1320a-7b(g) (emphasis added).
[6] Regeneron Pharms., Inc., 128 F.4th at 326; see also Andrew McGirty, Cracking Causation: The Need for a Workable Link Between the Anti-Kickback Statute and False Claims Act, 74 Case W. Rsrv. L. Rev. 429, 452-57 (discussing the opinions of the First, Third, Sixth, and Eighth Circuits).
[7] Univ. of Tex. S.W. Med. Ctr. v. Nassar, 570 U.S. 338, 346-47 (2013); Stuart M. Speiser, Charles F. Krause & Alfred W. Gans, 3 American Law of Torts § 11:6 (Monique C. M. Leahy, ed., 2025); see also Robin Dembroff & Issa Kohler-Hausmann, Supreme Confusion About Causality at the Supreme Court, 25 CUNY L. Rev. 57, 69-70 (2022) (discussing the but-for causation test under modern tort law and approaches to alleviating its ambiguity).
[8] United States ex rel. Greenfield v. Medco Health Sols., 880 F.3d 89, 100 (3d Cir. 2018).
[9] See, e.g., Nassar, 570 U.S. at 358 (“Even if the employer could escape judgment after trial, the lessened causation standard would make it far more difficult to dismiss dubious claims at the summary judgment stage.”); Nesbitt v. Candler Cnty., 945 F.3d 1355, 1358 (11th Cir. 2020) (“To avoid losing, [Plaintiff] argues for application of the motivating factor standard. That more plaintiff-friendly standard requires only a showing that the protected conduct ‘was a motivating factor for any employment [decision].’” (second alteration in original) (quoting Nassar, 570 U.S. at 349)).
[10] Regeneron Pharms., Inc., 128 F.4th at 327-38.
[11] Id. at 326.
[12] Id.
[13] Id.
[14] Id. at 326-27.
[15] Id.
[16] Regeneron Pharms., Inc., 128 F.4th at 327.
[17] Id.; Publication of OIG Special Advisory Bulletin on Patient Assistance Programs for Medicare Part D Enrollees, 70 Fed. Reg. 70623-03 (Nov. 22, 2005).
[18] Regeneron Pharms., Inc., 128 F.4th at 327; see Greenfield., 880 F.3d at 100 (“A kickback does not morph into a false claim unless a particular patient is exposed to an illegal recommendation or referral and a provider submits a claim for reimbursement pertaining to that patient.” (emphasis added)).
[19] Greenfield, 880 F.3d at 100.
[20] Regeneron Pharms., Inc., 128 F.4th at 327-38; see United States ex rel. Martin v. Hathaway, 63 F.4th 1043, 1052 (“The ordinary meaning of ‘resulting from’ is but-for causation.”).
[21] Martin, 63 F.4th at 1052-53; United States ex rel Cairns v. D.S. Med., LLC, 42 F.4th 828, 834 (8th Cir. 2022).
[22] Regeneron Pharms., Inc., 128 F.4th at 330.
[23] Id. at 329.
[24] Id. at 333 (“Under [the false certification] pathway, it is not the AKS violation itself that renders the claim false. Rather, it is the false representation that there is no AKS violation.”)
[25] Id. at 334.
[26] Id. 333-34.
[27] Stop Ill. Health Care Fraud, LLC v. Sayeed, 100 F.4th 899, 908 (7th Cir. 2024).
[28] Id. at 908-09 (acknowledging the current circuit split but declining explicitly adopt a precise standard for causation); see also United States ex rel Wilkerson v. Allergan Ltd., No. 22-CV-3013, 2025 WL 1181010, at *9-10 (N.D. Ill. Apr. 23, 2025) (relying on Regeneron in holding that “resulting from” indicates a but-for causation requirement).
[29] Compare Greenfield, 880 F.3d at 97 (finding that neither the Anti-Kickback Statute nor False Claims Act “requires a plaintiff to show that a kickback directly influenced a patient’s decision to use a particular medical provider”), with D.S. Med., LLC., 42 F.4th at 836-37 (“[W]hen a plaintiff seeks to establish falsity or fraud through the 2010 amendment, it must prove that a defendant would not have included particular ‘items or services’ but for the illegal kickbacks.”).
[30] See Hathaway, 63 F.4th at 1054 (requiring the government establish at least “one claim for reimbursement identified with particularity . . . that would not have occurred anyway” to meet causation requirements under an AKS-based FCA claim).
American Journal of Trial Advocacy 