Section 36B of the Internal Revenue Code, enacted as part of the Patient Protection and Affordable Care Act (ACA or the Act), makes tax credits available as a form of subsidy to individuals who purchase health insurance through marketplaces—known as “American

Health Benefit Exchanges,” or “Exchanges” for short—that are “established by the State under section 1311” of the Act. 26 U.S.C. § 36B(c)(2)(A)(i). On its face, this provision authorizes tax credits for insurance purchased on an Exchange established by one of the fifty states or the District of Columbia. See 42 U.S.C. § 18024(d). But the Internal Revenue Service has interpreted section 36B broadly to authorize the subsidy also for insurance purchased on an Exchange established by the federal government under

section 1321 of the Act. See 26 C.F.R. § 1.36B-2(a)(1) (hereinafter “IRS Rule”).

Appellants are a group of individuals and employers residing in states that did not establish Exchanges. For reasons we explain more fully below, the IRS’s interpretation of section 36B makes them subject to certain penalties under the ACA that they would rather not face. Believing that the IRS’s interpretation is inconsistent with section 36B, appellants challenge the regulation under the Administrative Procedure Act (APA), alleging that it is not “in accordance with law.” 5 U.S.C. § 706(2)(A).

On cross-motions for summary judgment, the district court rejected that challenge, granting the government’s motion and denying appellants’. See Halbig v. Sebelius, No.

13 Civ. 623 (PLF), 2014 WL 129023 (D.D.C. Jan. 15, 2014). After resolving several threshold issues related to its jurisdiction, the district court held that the ACA’s text,

structure, purpose, and legislative history make “clear that Congress intended to make premium tax credits available on both state-run and federally-facilitated Exchanges.” Id. at *18. Furthermore, the court held that even if the ACA were ambiguous, the IRS’s regulation would represent a permissible construction entitled to deference under Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837 (1984).

Appellants timely appealed the district court’s orders, and we have jurisdiction under 28 U.S.C. § 1291. Our review of the orders is de novo, and “[o]n an independent review of the record, we will uphold an agency action unless we find it to be ‘arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.’” Holland v. Nat’l Mining Ass’n, 309 F.3d 808, 814 (D.C. Cir. 2002) (quoting 5 U.S.C. § 706(2)(A)). Because we conclude that the ACA unambiguously restricts the section 36B subsidy to insurance

purchased on Exchanges “established by the State,” we reverse the district court and vacate the IRS’s regulation.