Monday's opening arguments on the health care law challenge at the U.S. Supreme Court will focus on a critical question that determines when this case gets decided.

For 90 minutes, the justices will hear arguments about their authority to hear the legal challenges to the 2010 Affordable Care Act, under a little-known law called the Tax Anti-Injunction Act of 1867. This will be a prelude to Tuesday's arguments on the central question facing the justices -- the constitutionality of the new law's mandate that Americans obtain health insurance.

The 1867 law prohibits the filing of a lawsuit to challenge a tax that hasn't been levied yet. Litigation to overturn the Affordable Care Act could be barred because the tax penalty for failing to obtain health insurance won't hit Americans until 2015.

Anti-Injunction Dimension To Case

Both sides in the legal challenges agree that the Anti-Injunction Act doesn't apply to the health care law. President Barack Obama's administration says the tax penalty is just a penalty, not a provision to raise revenue. Lawyers for the states challenging the health care law say their target is the individual mandate, not how it's enforced.

To argue the other viewpoint, the Supreme Court tapped Robert Long, a partner at the Washington law firm Covington & Burling.

In a survey of court watchers and experts, the justices are expected to let the case proceed and dive into the case's constitutional questions. Still, the justices have a chance to punt on deciding the constitutionality of the individual mandate to carry health insurance -- the most critical question they'll consider this week.