Set for oral argument on March 4, 2015, King v. Burwell brings to the Supreme Court yet another challenge to the Affordable Care Act (ACA). The King plaintiffs cite 26 U.S.C. § 36B to attack the validity of certain federal health insurance subsidies provided by the Internal Revenue Service (IRS) through the ACA. Specifically, because § 36B authorizes subsidies for low-income taxpayers who purchase health insurance from an “Exchange established by the State,” the plaintiffs allege that such subsidies are not valid on exchanges operated by the federal government where the states refused to operate a state-sponsored exchange. Given that the federal government operates exchanges in thirty-four states, the Supreme Court’s ruling will potentially affect nearly ten million taxpayers nationwide.