The Supreme Court heard oral arguments Wednesday in King v. Burwell, a challenge to ObamaCare. At issue is wording in the 2010 Affordable Care Act stipulating that premium tax credits—i.e., federal subsidies—are available for people who enroll in ObamaCare “through an exchange established by the State.”

In the hours since oral arguments, much of the talk has centered around Justice Anthony Kennedy’s suggestion that “from the standpoint of the dynamics of Federalism . . . there is something very powerful to the point that if...