The Affordable Care Act created state insurance Exchanges and a federal fallback when a State declined to establish one. Section 36B of the Internal Revenue Code authorizes refundable premium tax credits for qualifying taxpayers enrolled through “an Exchange established by the State under” the Act. Four Virginia residents argued that the phrase excluded federally operated Exchanges, which would have made their insurance more expensive and relieved them of the Act’s coverage requirement. The Supreme Court affirmed dismissal of their challenge to an IRS rule making credits available on both kinds of Exchange. Chief Justice Roberts’s majority opinion held that the question was too economically and politically significant for ordinary Chevron deference and therefore required the Court to interpret the statute itself. Although the statutory phrase could be read to limit credits to state Exchanges, the Act’s structure, related provisions, and interlocking reforms showed that Congress intended the Exchanges to function alike. Limiting credits to federal-Exchange States would undermine the coverage requirement and risk destabilizing insurance markets. Justice Scalia, joined by Justices Thomas and Alito, dissented, arguing that the majority rewrote clear statutory language and improperly prioritized the Act’s perceived purpose over Congress’s enacted words. The judgment of the Fourth Circuit was affirmed.