When the president signed the Affordable Care Act into law, it was pretty clear that the legislation would ultimately be decided by the U.S. Supreme Court. And now, two years later, the Supremes will be hearing its first arguments on the matter.

While hearings later on this week will deal with the constitutionality of the portion of the law requiring everyone to have insurance or pay a penalty come tax time, today’s 90-minute session deals with a little-discussed but crucial issue — whether or not anyone can challenge this piece of the legislation.

At issue is the 145-year-old Anti-Injunction Act, intended to stop people from suing over a tax provision that has yet to be enforced.

If the Supremes find that the Anti-Injunction Act both limits the court’s ability to rule on mandatory coverage before it’s enacted and that the act applies to this portion of the health care bill, then it would effectively delay any legal challenges on the mandatory coverage rule until at least 2014.

Of interest is the fact that neither the White House nor the Attorneys General from the states challenging the Affordable Care Act want to negate the challenges using the 19th Century legislation. Both sides would rather have the Supreme Court rule on health care reform as soon as possible.

So in addition to lawyers for the administration and the challengers, there will be a third lawyer, appointed by the court, to argue that the Anti-Injunction Act limits the court’s authority on yet-to-be enforced tax provisions and thus prevents the current challenges from going forward.

“The decision of the court of appeals should be vacated and remanded for dismissal of the Respondents’ challenge to [the mandate] for lack of jurisdiction,” reads the closing of this attorney’s written argument.

The U.S. Solicitor General will have 30 minutes to argue that while the Anti-Injunction Act does limit the court’s jurisdiction, it’s a non-issue because it does not apply, as the mandate and its penalties are not a tax like the ones the legislation was intended to protect.

And a lawyer for the challengers will get 20 minutes to argue that the Anti-Injunction Act does not actually prohibit the court from ruling on tax provisions.

The Justice Dept. had previously tried to invoke the Anti-Injunction Act in some of the lower-court challenges, with mixed success. As the cases climbed the appeals court ladder, that argument fell by the wayside.

For a law that’s been on the books for so long, the courts haven’t always had a consistent opinion of the Anti-Injunction Act (check out the SCOTUSblog review of the law and its potential impact on the Affordable Care Act here), so it’s hard to say on which side the Supremes will come down.

We’ll all find out when the court issues its ruling, most likely in early June.

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