The U.S. Supreme Court announced Monday that it will review a challenge to the Affordable Care Act's constitutionality after a group of states led by Texas claimed that there is no longer a legal justification for it.

The law, commonly known as ObamaCare, was first upheld by the Supreme Court under the justification that by tying the individual mandate -- the requirement to buy health insurance -- to a financial penalty it fell under Congress' taxation power. When President Trump eliminated the penalty, Republican-led states claimed there was no longer a legal basis for the mandate.

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The Fifth Circuit Court of Appeals ruled in December that part of the law is now unconstitutional and their decision cast a cloud over the rest.

“The individual mandate is unconstitutional because it can no longer be read as a tax, and there is no other constitutional provision that justifies this exercise of congressional power,” the ruling said. The court sent the case back down to a lower court to decide on whether the mandate is severable from the rest of the law, which would allow other parts of Obamacare to survive.

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A group of 20 Democratic states appealed. Defenders of the Affordable Care Act argued that the issues raised by the case are too important to let the litigation drag on for months or years in lower courts.

A decision from the Supreme Court is not expected until after the 2020 election.

The Associated Press contributed to this report.