(CNN) The fate of the Affordable Care Act lies in the Supreme Court's hands, and there's not much President-elect Joe Biden can do about it.
The justices will hear oral arguments Tuesday in the case that seeks to overturn the landmark health reform law. They will likely take initial votes at their private Friday conference and begin the process of writing opinions, though a decision isn't expected until the first half of 2021.
In a near-unprecedented step, the Trump administration is not defending the law, instead arguing that it should be declared unconstitutional. By the time Biden takes office on January 20, it may be too late for his administration to have much influence on the court's decision.
Plus, the case will continue even if Biden switches sides and starts backing the Affordable Care Act since the original lawsuit was brought by a coalition of Republican state attorneys general.
"The Biden administration's options are pretty limited," said Nicholas Bagley, law professor at the University of Michigan. It "could drop the Justice Department's support for the lawsuit, but that won't make the case go away because the red state plaintiffs will still push it forward."
And while lawmakers could take steps to render the case moot, they are unlikely to do so in a divided Congress. Control of the Senate could depend on likely runoffs in January for the two Georgia seats. Democrats are poised to make the preservation of the law a centerpiece of their campaigns.
"Tomorrow health care is on the line at the Supreme Court," Rev. Raphael Warnock, one of the Senate Democratic candidates, tweeted late Monday. "On January 5th health care is on the ballot for Georgians."
The continued existence of the Affordable Care Act is central to Biden's health care policy proposals. He wants to expand coverage by beefing up Obamacare's federal premium subsidies, so more people could afford to buy plans on the exchanges, and by adding a government-run public option, which in theory would have lower monthly premiums.
Biden will speak on Tuesday in Delaware about the Supreme Court case and his plans going forward.
"President-elect Biden has laid out a comprehensive plan to build on the Affordable Care Act, lower health care costs, and expand coverage -- something that's vitally important right now in the middle of a pandemic -- and once in office Biden's going to work to deliver on that plan," Biden spokesman Mike Gwin said.
The case stems from a 2018 lawsuit brought by a coalition of Republican state attorneys general led by Texas who argue that the individual mandate is unconstitutional because Congress reduced the penalty for not having health insurance to zero as part of the 2017 Republican tax cuts. And, as a result, the entire law must fall.
The Trump administration joined the coalition several months later, arguing initially that only key provisions that protect those with pre-existing conditions must be overturned and then that the entire law must go. In its latest briefs, the Justice Department says that the judgment should only apply in the states that brought the lawsuit -- though effectively, it would kill Obamacare in the entire country, Bagley said.
Since Trump is not defending the law, a group of Democratic attorneys general led by California and the Democratic-led House of Representatives stepped in to do so.
So far, two lower courts have sided with the GOP states and the Trump administration that the individual mandate is unconstitutional, though an appellate panel last year punted on deciding the fate of the rest of the law. It sent the case back to the lower court.
At stake is more than just the health insurance coverage for more than 20 million people who are enrolled in Obamacare plans or who benefit from law's expansion of Medicaid to low-income Americans. The decade-old act is now part of the fabric of the nation's health care system, affecting nearly everyone.
Among its most popular measures are its ban on insurers denying people coverage or basing premiums on their health histories and its provision to allow children to stay on their parents' policies until the age of 26. The Affordable Care Act also mandates free preventive care and birth control.
President Donald Trump has repeatedly said he would unveil a plan that would replace Obamacare and continue to protect people with pre-existing conditions, but he has failed to do so.
Lawmakers, however, could take one of several steps to address the issue at the center of the case, experts said.
Congress could eliminate the individual mandate that requires most Americans to have health insurance. Or it could set the penalty for not having coverage at a nominal sum, such as $1. Or it could clarify that the mandate is, in fact, severable from the rest of the law.
But none of these options would be simple to execute, especially without a solid Democratic majority in the Senate.
"Those are all three things that could be done," said Jonathan Adler, a law professor at Case Western Reserve University and longtime critic of the Affordable Care Act. "All of them would require legislative cooperation, which would require the Senate to go along, which obviously, the Senate may or may not be willing to go along with."