Lawyers representing almost 40 states as well as the House of Representatives clashed on Tuesday over the fate of the Affordable Care Act (ACA) in a New Orleans appellate court in a case that could have monumental effects on millions of Americans.

On one side are the lawyers for the Trump administration and for 18 Republican states. On the other side are attorneys representing 20 Democratic states, as well as the House of Representatives. The two forces will be giving oral arguments to a panel of three judges on the 5th U.S. Circuit Court of Appeals which will decide whether or not to strike down ObamaCare. Representing Louisiana, Texas and Mississippi, the 5th Circuit is one of the most conservative courts in the country, ensuring that this case will most likely be appealed and end up in the Supreme Court.

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The case revolves around the individual mandate aspect of the ACA which requires all Americans to get health insurance or pay a penalty. The 2017 Republican tax cut bill reduced that penalty to $0, and now the GOP is arguing that the change in price makes the mandate unconstitutional. The coalition of Republican states which brought this challenge to court in the first place argues that as the mandate no longer brings in any money, it undermines the basis of the Supreme Court’s 2012 decision to uphold the law based on Congress’ tax power. A federal court in Texas first sided with the Republicans, prompting it to be appealed and resulting in the current legal battle in the appellate court.

The Democrats contest that the mandate remains constitutional and that even if wasn’t, the rest of the law should continue to stand without it. They also argue that eliminating ObamaCare and the protections for those with pre-existing conditions that it enshrines would grievously harm millions of Americans.