About these facts, there is no dispute. The question is whether, when running an exchange in lieu of a state, the federal government can operate it in the same way—in particular, whether the federal government has authority to offer those subsidies. These tax credits, available to people on a sliding scale depending on income, will be worth as much as several thousand dollars a year in some cases. They will enable millions of Americans to get comprehensive health insurance, the kind they cannot now because the coverage is too expensive or simply unavailable. Without the subsidies, these people couldn’t get coverage and, quite possibly, the exchanges as a whole would cease to function because they could not maintain a good actuarial balance.

Cannon and Adler, along with the state of Oklahoma and others embracing this cause, argue that the federal government lacks authority to offer those subsidies. Roughly speaking, their reasoning goes like this: The section of the law describing subsidies specifies that Washington may offer them in state-run exchanges, but has no parallel language specifying that Washington may offer them in federally run substitutes. And this omission, Cannon and Adler insist, was no accident. The Senate wanted the states, not Washington, to run the exchanges. And since the federal government can’t order states to do something—that’s called “commandeering”—it had to offer financial incentives. Withholding subsidies unless states ran the exchanges, Cannon and Adler say, was one of those incentives:

The language, structure, legislative history, and congressional debate over the PPACA demonstrate that its authors preferred state-run Exchanges to federal Exchanges. From the outset, the Act directs states to establish Exchanges and many PPACA’s supporters presumed that all states would create exchanges of their own. While the Act authorizes the federal government to establish Exchanges for states that fail to comply with the PPACA’s direction, these exchanges are intended to serve as a fallback, and were not intended to replace state-run exchanges.

The emphasis is mine, because this is really the heart of the case. According to Cannon and Adler, the Senate wanted a system in which states that failed to create exchanges could deprive their citizens of subsidies.

Not too many legal experts seem to think the lawsuit has merit. (Then again, the legal establishment said the same thing about the original lawsuits challenging the constitutionality of the whole law had merit, and those suits came within one very narrow vote of winning at the Supreme Court.) Among the skeptics is Samuel Bagenstos, a professor at the University of Michgan and a widely respected expert on constitutional law. In a recently posted series of blog posts, Bagenstos says Cannon and Adler are reading the statute in an unusually pinched way. The law may not specify that the federal government may offer subsidies when it operates exchanges, Bagenstos says, but elsewhere it talks about the federal government running exchanges in lieu of recalcitrant states. Clearly, Bagenstos says, the Senate bill’s architects wanted these substitute exchanges to be fully functional, complete with subsidies. The whole point was to have the feds do what the states would not. "It is implausible to think that Congress would have intended to create a statute that was so at war with itself,” Bagenstos concludes, “and that rendered largely useless its crucial backup provision for federally-operated exchanges.”