McCollum was particularly outraged that the federal government would order states to nearly double the number of people they accept into the state-federal Medicaid health coverage safety net. Refusal would mean the loss of all federal support for the huge program.

The court indicated it will consider that and these core questions:

1. Does Congress have the authority to require nearly all Americans to purchase health insurance?

2. If not, can the individual mandate be struck down while leaving the rest of the act in place?

3. Since the individual mandate is enforced with a tax penalty that hasn't even been applied to any one yet - $95 starting in 2014 for people who choose not to be insured - can questions 1 and 2 even be legitimately raised before 2015?

This third question could be key, as even some conservative judges at the lower court level have concluded that the case cannot go before the courts until after tax returns are paid in 2015, said Ian Millhiser, policy analyst for the Center for American Progress in Washington.