The National Federation of Independent Business, several individuals, and 26 States challenged the Affordable Care Act’s individual mandate and Medicaid expansion. The Supreme Court held that the Anti-Injunction Act did not bar the suit because the Act called the shared-responsibility payment a penalty, not a tax. The individual mandate could not be sustained under the Commerce or Necessary-and-Proper Clauses because Congress may regulate existing commercial activity but may not compel inactive people to enter commerce. The payment nevertheless could reasonably be construed as a tax within Congress’s taxing power: it was collected by the IRS, was not so high that it eliminated the choice not to buy insurance, and imposed no separate legal consequence for going uninsured. The Court also held that the Medicaid expansion became unconstitutionally coercive because the Secretary could withdraw a State’s existing Medicaid funds if the State declined to participate in the substantially enlarged program. The remedy was to bar that withholding while leaving the expansion and the remainder of the Act available to participating States. The judgment was affirmed in part and reversed in part. Justice Ginsburg concurred in part and dissented in part; Justices Scalia, Kennedy, Thomas, and Alito dissented in a joint opinion, and Justice Thomas separately dissented.