Since Congress amended the AKS in 2010 to articulate a specific nexus between kickbacks and false claims, courts have grappled with the appropriate causation standard required to substantiate those claims. In 2018, the Third Circuit held that the government need only show a “causal connection” between the unlawful kickback and the submission of the reimbursement claim.[1] But the Sixth, Eighth, and, most recently, the First Circuits have adopted a more exacting causation standard, requiring a showing of “but-for” causation. Under this heightened standard, the government (or a qui tam relator) must prove that a claim would not have been submitted but-for the alleged kickback.[2]
While growing consensus around this stringent causation standard offers promise of constraining potential FCA exposure, in response, the Department of Justice (DOJ) has recently pivoted back to the false certification theory of AKS-based FCA liability it championed prior to the adoption of the 2010 amendment. In a recent First Circuit case, the government argued that the 2010 amendment to the AKS did not preclude FCA liability under the false certification theory, and the court agreed.[3] Defendants should expect the DOJ and relators to embrace the false certification theory – at least in the alternative – as a tactical device to sidestep the rigorous but-for causation standard.
The rise of the but-for causation standard
Under the AKS, it is a criminal offense for anyone to “knowingly and willfully” offer or pay remuneration – such as kickbacks, bribes, or rebates – to another person in order to induce that person to purchase or order any good, facility, or service for which payment could be made under a federal health care program. In 2010, Congress amended the statute so that “a claim [for payment by a federal health care program] that includes items or services resulting from a violation of [the AKS] constitutes a false or fraudulent claim for purposes of” the FCA. Pursuant to this amendment, any claim submitted to a federal health care program that includes items or services “resulting from” an AKS violation is automatically deemed a false or fraudulent claim under the FCA.
Following the 2010 amendment, jurisdictions have split into two camps on what it means for a claim to “result from” a violation of the AKS. The Third Circuit adopted a relatively lenient causation standard in Greenfield v. Medco (Greenfield), requiring only a “sufficient causal connection” between the kickback scheme and the reimbursement claim.[4] Thus a plaintiff need not “show that a kickback directly influenced a patient's decision to use a particular medical provider;” instead, they simply have to demonstrate “some connection between a kickback and a subsequent reimbursement claim.”[5] While the court stated “the taint of a kickback” does not “render[ ] every reimbursement claim false,” it noted a kickback will morph into a false claim where “a particular patient is exposed to an illegal recommendation or referral and a provider submits a claim for reimbursement pertaining to that patient.”[6]
Since Greenfield, however, other circuits have rejected the “sufficient causal connection” test. Recently, the First Circuit joined the Sixth and Eighth Circuits[7] in adopting a more rigorous but-for causation standard, holding that “to demonstrate falsity under the 2010 amendment, the government must show that an illicit kickback was the but-for cause of a submitted claim.”[8] This decision reflects a growing consensus across circuits in favor of the but-for causation standard.
The government’s countermove: False certification theory
To avoid this heightened standard, the DOJ has fallen back on an alternative, older theory of liability in AKS FCA cases: the false certification theory. Under this approach, the government alleges that while submitting claims for reimbursement, a defendant certifies compliance with the AKS or another relevant statute. This false certification could be express (where a company states its compliance with the relevant statute on the face of the claim) or implied (where the act of submitting a claim is deemed a certification of compliance with statute material to payment of the claim). For AKS cases, this theory allows the government to argue that the falsity lies not in the causal link between a kickback and a specific claim, but in the mere act of representing compliance with the law when AKS violations allegedly exist.
When the First Circuit required but-for causation under the 2010 AKS amendment, it also explained “there is nothing in the 2010 amendment that requires proof of but-for causation in a false-certification FCA case.”[9] Following the First Circuit’s ruling, the government moved the District Court for leave to reopen discovery and submit a renewed motion for partial summary judgment based on the false certification theory.[10] The District of Massachusetts permitted the government to pursue this theory – even though “‘false certification’ was never explicitly stated as a theory of liability in the complaint” – explaining that claims under the false certification theory “run on a separate track” than those under the 2010 AKS amendment.[11] The Court also confirmed that “[i]n contrast” to allegations under the 2010 AKS amendment, to prove violation under the false certification theory, the government need not prove “‘the AKS violation was the but-for cause of the false claim’ submitted to the government.”[12]
The District of Massachusetts is not alone in permitting the government and qui tam relators to pursue the false certification theory as an alternative route to liability in AKS-based FCA cases; other jurisdictions have, in non-intervened qui tam cases, treated false certification as a distinct and viable way to prove liability under the FCA. For example, in United States ex rel. Wilkerson & Jackson v. Allergan Ltd., the Northern District of Illinois adopted the but-for causation standard of the First, Sixth, and Eighth Circuits (finding the Third Circuit’s more lenient causation standard “not persuasive”) while also explaining that “a cause of action for falsely certifying compliance with the AKS exists and does not require alleging but-for causation.”[13] Several other District Courts have taken a similar approach.[14] Collectively, these cases underscore a growing pattern: even as courts embrace a stricter causation requirement under the 2010 amendment to the AKS, they continue to permit false certification to operate as an alternative pathway to liability.
The emerging two-track landscape
Taken together, these developments reveal dual enforcement tracks. On one track, the DOJ and qui tam relators continue to push for the more lenient Third Circuit Greenfield approach to causation. The government has not had success of late with this approach in multiple circuits, where it argued for a “sufficient causal connection” standard but ultimately lost. On the other track, the DOJ is embracing a false certification theory as a backstop for establishing liability in AKS-based FCA cases.
Given that the government may argue in the alternative for both of these paths to liability, defendants must prepare to defend against certification-based theories. As an initial matter, defendants can push back where the government lacks evidence of actual false claims.[15] Indeed, “aggregate data together with strong circumstantial evidence” is insufficient “to overcome summary judgment” “in an FCA case” absent actual “proof … demonstrat[ing] the existence of false claims.”[16]
Defenses based on the familiar elements of FCA liability including scienter and materiality are also available.[17] These “rigorous”[18] requirements are strong defenses to the false certification approach. For example, with respect to scienter, defendants can argue that allegedly false certifications are only actionable when the certification was knowingly false at the time it was made or when the defendant knowingly caused another entity to submit the certification.[19]
Defendants can also contend that the FCA’s structure should not permit the government to bypass causation entirely.[20] The FCA requires that a defendant must have “caused” a false claim “to be presented” or “caused” a false statement “to be made or used” under § 3729(a)(1)(A)–(B).[21] While but-for causation may not be required to prove falsity under the false certification theory, defendants can argue that proving liability requires that the government must still prove that the defendant’s conduct caused the submission of a false claim or false statement.
Further, as recently recognized in United States ex rel. Louderback v. Sunovion Pharmaceuticals, Inc. (Louderback), a non-intervened AKS/FCA case, defendants may also have textual and legislative interpretation arguments against allowing the government to treat false certification as an end-run around the 2010 AKS amendment’s causation requirements.[22] The Louderback court explained that allowing AKS-based FCA cases to proceed under a false certification theory would be “a flawed interpretation of [the 2010 AKS amendment]” and would result in the statute “hav[ing] little practical effect” because “[w]hat [AKS]/[FCA] relator would go to the trouble of attempting to allege a claim under § 1320a-7b(g) and meet its but-for causation standard when a less demanding path is available?”[23] This position, however, has already been rejected by numerous District Courts that have allowed relators (and the government) to proceed under a false certification theory.[24]
Future litigation will test how these approaches interact, particularly when underlying conduct can support both 2010 AKS amendment-based and certification-based claims. Key among these open litigation questions are questions of proof rarely if ever litigated in certification cases, like the types and quantum of evidence required for a plaintiff (government or relator) to identify the universe of claims and the measure of damages in certification case. Defendants should expect the government to plead both theories, potentially expanding the scope of discovery and broadening opportunities for the strategic attack.
Looking ahead
The enforcement environment under the FCA and AKS will likely remain dynamic through 2026 and beyond. The expansion of the but-for causation standard means defendants are more likely than ever to succeed in challenging and shrinking FCA claims predicated on the 2010 amendment to the AKS. The government’s pivot to false certification, however, marks a strategic adjustment. Defendants should anticipate heightened scrutiny of certifications made in Medicare, Medicaid, and other federal reimbursement claims. Courts will also likely continue to create precedent delineating the boundary between legitimate certification-based liability and impermissible workarounds to established causation standards. In the meantime, robust documentation, transparency, and compliance training remain the best defenses to these emerging theories of liability.
References
[1] United States ex rel. Greenfield v. Medco Health Solutions Inc., 880 F.3d 89, 100 (3d Cir. 2018).
[2] United States ex rel. Cairns v. D.S. Med. LLC, 42 F.4th 828, 834–35 (8th Cir. 2022); United States ex rel. Martin v. Hathaway, 63 F.4th 1043, 1052–55 (6th Cir. 2023); United States v. Regeneron Pharms., Inc., 128 F.4th 324 (1st Cir. 2025).
[3] Regeneron, 128 F.4th 324 (1st Cir. 2025).
[4] United States ex rel. Greenfield v. Medco Health Solutions Inc., 880 F.3d 89, 100 (3d Cir. 2018).
[5] Id.
[6] Id.
[7] United States ex rel. Martin v. Hathaway, 63 F.4th 1043, 1052–55 (6th Cir. 2023); United States ex rel. Cairns v. D.S. Med. LLC, 42 F.4th 828, 834–35 (8th Cir. 2022).
[8] Regeneron, 128 F.4th at 333.
[9] Id. at 334.
[10] United States v. Regeneron Pharms., Inc., 793 F.Supp.3d 261, 265 (D. Mass. 2025).
[11] Id. at 267 (also noting that “the complaint alleges sufficient facts to state a plausible claim for violation of the FCA under a false-certification theory”).
[12] Id. at 266 (citations omitted).
[13] No. 22-CV-30130, Dkt. No. 196 at 23, 37 (N.D. Ill. 2025). Ultimately the court dismissed relators’ false certification claims for failure to state a claim and allowed only some AKS/FCA claims to proceed. Id. at 43, 48, 54.
[14] United States ex rel. Schroeder v. Hutchinson Reg’l Med. Ctr., 777 F. Supp. 3d 1256, 1262–63, 1275–79, 1281–84 (D. Kan. 2025) (evaluating relator’s 2010 AKS Amendment counts and false certification counts at summary judgment); United States ex rel. Heller v. Guardian Pharmacy of Atlanta, LLC, No. 1:18-CV-03728-SDG, 2024 WL 102211, at *2 (N.D. Ga. Jan. 9, 2024) (citing Urquilla-Diaz v. Kaplan Univ., 780 F.3d 1039, 1045 (11th Cir. 2015)) (confirming that “[r]egardless of how the Eleventh Circuit interprets [the 2010 AKS Amendment] . . . the Court has already determined that [relator’s] alternative theory of causation, implied certification, should proceed to trial”); United States ex rel. Fesenmaier v. Cameron-Ehlen Grp., Inc., No. 13-CV-3003 (WMW/DTS), 2023 WL 36174, at *1 (D. Minn. Jan. 4, 2023) (allowing certification-based theories to proceed to trial, even where but-for causation had not been demonstrated as to every claim).
[15] See, e.g., Def. Regeneron Pharmaceuticals, Inc.’s Mem. in Opp.to the United States’ Second Mot. for Partial Summ. J., Dkt. No. 416, at 9–17, United States v. Regeneron Pharms., Inc., No. 20‑11217‑FDS (D. Mass. Nov. 5, 2025).
[16] United States ex rel. Booker v. Pfizer, Inc., 847 F.3d 52, 58 (1st Cir. 2017).
[17] See 1:20-cv-11217, Dkt. No. 416.
[18] Universal Health Servs., Inc. v. United States ex rel. Escobar, 579 U.S. 176, 192, 196 n.6 (2016).
[19] Id. at 181; see also Regeneron Opp. to Second Motion for Summ. J., Dkt. No. 416, at 6–9.
[20] Regeneron Opp. to Second Motion for Summ. J., Dkt. No. 416, at 17, 23–24 (contending the government cannot “ask[] this Court to ignore clear statutory text and adopt a causation standard that ‘requires no proof of actual causation at all’” (citing Regeneron, 128 F.4th at 331)).
[21] Id. at 17–19.
[22] United States ex rel. Louderback v. Sunovion Pharms., Inc., 703 F. Supp. 3d 961 (D. Minn. 2023).
[23] Id. at 979–80; Regeneron Opp. to Second Motion for Summ. J., Dkt. No. 416, at 19–23.
[24] See, e.g., Regeneron Pharms., Inc., 793 F.Supp.3d at 265; Wilkerson, No. 22-CV-30130, Dkt. No. 196 at 23; Schroeder, 777 F. Supp. 3d at 1262–63; Heller, LLC, 2024 WL 102211, at *2; Fesenmaier, 2023 WL 36174, at *1.