Republicans have vowed to begin dismantling the politically-divisive health care law when they take control of the U.S. House in January.
But as long as President Barack Obama wields a White House veto pen, it's unlikely they'll succeed in repealing the law outright, and that means the battle is likely to play out in the courts.
Several federal judges have already weighed in on the constitutionality of the health care law. Some have upheld it; others have ruled against key parts.
Most prominently a Virginia judge ruled a key part of the law unconstitutional: the requirement that every American buy health insurance or face a penalty.
Many experts view that mandate as the lynchpin of the law's insurance reforms.
The theory is that many people who go without insurance now are healthy. They don't buy insurance because they don't feel they need it. The law's mandate is premised on the general idea that requiring everyone to pay for insurance will help cover the health costs of sicklier people.
But does Congress have the power to require every American to buy health insurance?
Congress does have broad power to regulate economic activity under the Constitution's commerce clause, said William Mitchell Law Professor Mehmet Konar-Steenberg. The question is whether Congress is trying to regulate an economic activity here.
Opponents argue there is no economic activity for Congress to regulate -- because people who don't buy insurance are not engaging in commerce.
"The argument that's made is that this case is different because we're about passivity," Steenberg said. "We're talking about Congress regulating people for their failure to engage in an activity ... in particular for their failure to purchase health insurance."
Steenberg said the counter argument is that even people who don't buy insurance will use the health care system, and as a result engage in an economic activity.
"Everybody consumes health care," Steenberg said. "Some people consume it by means of an insurance policy they have with a private insurer. Other people insure it by going to the emergency room when things have gotten so bad they have to go there be cause they don't have insurance."
University of Minnesota Law Professor Amy Monahan said there's another part of the Constitution that's also at play -- Congress' broad power to tax. As part of the individual mandate, those who fail to buy insurance could pay a penalty.
"Conventional wisdom is that it's pretty easy for a tax to be constitutional," she said. "That said, arguments are being made that we shouldn't even think of this as a tax, it's simply not about raising revenue, it's about getting people to buy health insurance and just because you've included it in the tax code and set it up as a tax, doesn't make it a tax."
These cases will wind their way through the federal court system eventually reaching the Supreme Court. Vanderbilt Law Professor James Blumstein said it's hard to gauge how the justices may vote. But based on past cases, he has a theory that there'll probably be four votes that support the federal government's power to mandate insurance.
"These are folks who would believe in national power and national authority," he said. "I think there are probably several justices, maybe four inclined to be more skeptical about this pushing of the envelope as this federal law does and who might be wanting to rein it in. And of course as so many of these cases, Justice Kennedy is sitting as the enigmatic fifth vote."
Authorities say the legal challenges should move their way through the lower courts during the next year or two, which they say should be in time for the Supreme Court to make its decision before the mandate takes effect.