Opinion of the Court
Federal Exchange is not "an Exchange established by the State under [42 U. S. C. §18031]," and that the IRS Rule therefore contradicts Section 36B. Brief for Petitioners 18–20. The Government responds that the IRS Rule is lawful because the phrase “an Exchange established by the State under [42 U. S. C. §18031]” should be read to include Federal Exchanges. Brief for Respondents 20–25.
When analyzing an agency’s interpretation of a statute, we often apply the two-step framework announced in Chevron, 467 U. S. 837. Under that framework, we ask whether the statute is ambiguous and, if so, whether the agency’s interpretation is reasonable. Id., at 842–843. This approach “is premised on the theory that a statute's ambiguity constitutes an implicit delegation from Congress to the agency to fill in the statutory gaps."FDA v. Brown & Williamson Tobacco Corp., 529 U. S. 120, 159 (2000). "In extraordinary cases, however, there may be reason to hesitate before concluding that Congress has intended such an implicit delegation." Ibid.
This is one of those cases. The tax credits are among the Act’s key reforms, involving billions of dollars in spending each year and affecting the price of health insurance for millions of people. Whether those credits are available on Federal Exchanges is thus a question of deep "economic and political significance" that is central to this statutory scheme; had Congress wished to assign that question to an agency, it surely would have done so expressly. Utility Air Regulatory Group v. EPA, 573 U. S. ___, ___ (2014) (slip op., at 19) (quoting Brown & Williamson, 529 U. S., at 160). It is especially unlikely that Congress would have delegated this decision to the IRS, which has no expertise in crafting health insurance policy of this sort. See Gonzales v. Oregon, 546 U. S. 243, 266–267 (2006). This is not a case for the IRS.
It is instead our task to determine the correct reading of Section 36B. If the statutory language is plain, we must
