The Supreme Court has agreed to hear an appeal case on the Affordable Care Act (ACA), commonly known as Obamacare, that could potentially invalidate the entire law.

On Dec. 15, 2018, a Texas judge ruled that Obamacare’s individual mandate was unconstitutional. Judge Reed O’Connor agreed with the plaintiffs who argued that the lack of a penalty invalidated the “individual mandate” provision of the law, and if that part of the law was now invalid, then the whole law was.

Democratic states and the House of Representatives appealed the decision, and the case made it all the way up to the Supreme Court in a case titled California v. Texas. The court has not yet scheduled oral arguments, but a decision is expected close to the end of its 2021 term. If the conservative-majority justices find the individual mandate unconstitutional, that could mean all of the ACA is unconstitutional.

View photos U.S. President Barack Obama gestures in Washington D.C., on December 16, 2016. (Photo: REUTERS/Carlos Barria) More

“There could be essentially total chaos,” Cynthia Cox, director for the Program on the Affordable Care Act at the Kaiser Family Foundation, told Yahoo Finance. “There’s no replacement plan that is ready to go and so essentially what would happen next is possibly over a short period of time, or possibly immediately, we would start seeing the ACA being unwound. And the immediate effect would be that literally tens of millions of people could lose coverage and also even more people could have other changes to their coverage.”

According to the U.S. Census Bureau, the uninsured rate increased from 2017 to 2018 — the first year-to-year increase in the uninsured percentage since 2008 to 2009. In 2017, 25.6 million people were uninsured and that number increased to 27.4 million people in 2018, a 0.5% increase. A key part of Obamacare involved lowering the number of Americans without health insurance.

“What [would] happen is we’re going to go back to a marketplace that we had before the ACA,” Gerald Kominski, a professor in health policy and management at UCLA Fielding School of Public Health, told Yahoo Finance. “Roll back the clock 11 years. First of all, there are no longer subsidies for people to buy health insurance in exchanges. Exchanges go away.”

View photos Ivan Mendoza, MD, associate medical director for the Jackson Medical Group's cardiology practice, (L) speaks with Felipe Finale, 78, on September 8, 2016 in Miami, Florida. (Photo: Joe Raedle/Getty Images) More

Kominski added that it would “be up to the court to determine whether or not the ruling is immediately effective or whether or not there is an opportunity. For example, most insurance enrollment takes place at the beginning of the calendar year and extends through that year. It could be that the eligibility would be allowed to continue for a year, but it’s possible that it could be effective immediately.”

Furthermore, others may lose certain benefits currently received through employer insurance.

“Tens of millions more who get their coverage through employers would also lose important benefits,” Tara Straw, a senior policy analyst at the Center for Budget and Policy Priorities, told Yahoo Finance. “As they did prior to the ACA, insurers could impose annual and lifetime limits on coverage, limit the ability of young adults to stay on their parents’ health plans, reimpose cost sharing for preventive services, and more.”

The individual mandate

The crux of the case is the individual mandate component of Obamacare. The individual mandate is the fee you pay if you choose not to buy health insurance if you can afford it.