Doctors, patients, politicians and legal scholars are eagerly awaiting the Supreme Court's decision on President Barack Obama's health care program on Thursday. But there's one group that is really on pins and needles: accountants and other number crunchers.

If the court overturns the Patient Protection and Affordable Care Act, they're the ones who'll have to figure out what's going to happen to the $1 billion the federal government has already handed out to states and territories to establish state-regulated health care plans to help find public or private insurance for Americans eligible for federal subsidies.

The court has three main options — it can uphold the entire law, strike down the entire law or strike down parts of it.

Some justices appeared to signal during arguments in March that they were skeptical of the law, especially the so-called individual mandate, the provision requiring people to buy insurance or pay a fine. Because of the mandate, the Obama administration insisted on provisions directing the states to set up the insurance plans, called health insurance exchanges, to find discounted coverage for uninsured or hard-to-insure people.

Among them was Chief Justice John Roberts, who questioned whether the government can compel people to buy any product.

"Can the government require you to buy a cell phone because that would facilitate responding when you need emergency services?" he asked.

Justice Antonin Scalia drew a similar analogy.

"Everybody has to buy food sooner or later. So you define the market as food, therefore everybody is in the market," he said during the March arguments. "Therefore, you can make people buy broccoli."

What's worrying for supporters of the law is that it appears likely that Roberts will personally craft the ruling, said Tom Goldstein, the publisher of SCOTUSblog— SCOTUS is shorthand for Supreme Court of the United States.

"John Roberts hasn't done anything, really, in major cases in March and April, at the end of the term, which means it's very likely that he assigned that decision to himself," Goldstein told NBC News.

If that part of the law is upheld, the insurance plans must be in operation by 2014. But what if it isn't?

No one really knows.

That includes the White House, which has consistently said it expects the law to be upheld and is moving ahead accordingly.

"Once that decision is rendered, we will make decisions about what to say about it," press secretary Jay Carney said Tuesday.

If the law is overturned, there's nothing to stop the federal government from trying to recoup the money it has already distributed for the exchanges — a total of $1.015 billion to 49 states and a multistate planning project, according to an msnbc.com analysis of state disbursement figures provided by the Department of Health and Human Services.

"If the whole thing really is unconstitutional, that has to mean that it is illegal to spend the money that way under current law," Joseph Antos, a health care analyst with the American Enterprise Institute, a conservative Washington policy institute, told Kaiser Health News.

Kaiser adds:

Retrieving unspent funds might be possible, but collecting money that's already been spent could prove problematic, especially for cash-strapped states still dealing with a weak economy.

"My sense would be they would not recover the money. How do you recover the money? If it's spent, what do you do?" said Steven Lieberman, the president of Lieberman Consulting Inc. and the former deputy executive director for policy at the National Governors Association.

Nor is it clear what the states would do. Nineteen states have put their plans on hold pending the Supreme Court ruling, according to the Center for Budget and Policy Priorities(.pdf), but others — among them New York, Massachusetts and California — have signaled that they'll try to implement exchanges anyway.

Another is Utah, where 30 percent of the people getting insurance under the exchange are doing so for the first time, said Patty Conner, director of the insurance exchange in Utah.

That makes the plan "a good value to the state," Conner said, as reported by the Deseret News of Salt Lake City.

And private insurers have indicated that they'll also go ahead with some of the law's provisions if it's struck down.

Three of the nation's largest carriers — United Healthcare, Aetna and Humana — said this month that they would continue to let parents keep their children on their policies up to age 26, one of the most popular provisions of the entire plan, and would continue offering preventive services without copayments.

United Healthcare and Humana (but not Aetna) also promised not to reinstate lifetime limits on coverage or cancel policies retroactively, two other provisions widely welcomed by analysts and patients' advocates.

Even so, the picture is complicated by the fact that there's nothing to stop lawmakers from trying again to reform the health-care system if the law falls.

"If this goes away, we still have to start dealing with the problem," Rep. Darrell Issa, R-Calif., a member of the Ways and Means Committee, said Sunday on NBC's "Meet the Press."

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