A medical group has asked to intervene in the U.S. Supreme Court case to determine the constitutionality of President Obama’s 2010 health care law, challenging the characterization of the penalty for not buying health insurance as a tax.

The request was made by the Association of American Physicians & Surgeons on Thursday.

Before determining the constitutionality of the Affordable Care Act, the Supreme Court must decide whether or not the law can even be challenged. The Anti-Injunction Act prevents taxpayers from challenging a tax before it goes into effect, which could push any legal challenge back to 2015, after the individual mandate requiring Americans to obtain health insurance kicks in.

In September the Virginia-based 4th Circuit court of appeals cited the Anti-Injunction Act to dismiss the case.

“When Democratic legislators railroaded ObamaCare through Congress in March 2010, they insisted that it did not impose a tax,” stated AAPS. “But at the 11th hour, a new argument has been raised asserting that the penalty in ObamaCare is somehow a tax, and that therefore the Court lacks the power to review it.”

In November the Supreme Court agreed to hear an appeal to the Atlanta-based 11th Circuit court decision to strike down the individual mandate but leave intact the rest of the ACA. A decision on the appeal will be handed down by June.

The AAPS claimed the ACA is “harming medical practices and patients already, regardless of the label on its penalty,” and noted the association has the legal standing to challenge the ACA on behalf of member physicians.

A decision by the Supreme Court on AAPS's motion may come as soon as Monday.