If the U.S. Supreme Court rules in favor of the plaintiffs in a case involving the Affordable Care Act and its tax subsidies, over 270,000 Illinoisans could be impacted, according to the U.S. Department of Health and Human Services.

According to an agency report, ACA health care subsidies worth as much as $680 million could be invalidated for hundreds of thousands of Illinoisans if the nation's high court agrees with the plaintiffs' arguments that Obamacare tax subsidies were not intended for people purchasing insurance through the federal government's exchange. 

The challengers of President Barack Obama's signature health reform law claim the tax subsidies were meant only for people in the 13 states and the District of Columbia that operate their own insurance marketplaces.

The U.S. Supreme Court heard oral arguments on the case, King v. Burwell, last week and is expected to hand down a decision by the end of June.

Republican Gov. Bruce Rauner plans to "take appropriate action depending on how the Supreme Court rules," his office said, the Associated Press reports.