The United States Court of Appeals for the District of Columbia Circuit recently heard oral arguments in two cases challenging a signature aspect of President Obama’s energy plan.

In June 2014, the Environmental Protection Agency proposed a Clean Power Plan, intended to cut carbon-dioxide emissions 30 percent, from 2005 levels, by 2030.

Critics of the proposed plan say these regulations would radically transform the energy sector, effectively banning the construction of new coal-fired power plants—a reliable energy resource that currently generates more than 39 percent of the country’s electricity.

Proponents of the plan say the regulations are needed to curb planet-warming carbon emissions.

Because the states filed their lawsuit before the EPA has finalized their plan, there is a chance the judges could determine the lawsuit premature.

Hans von Spakovsky, senior legal fellow at The Heritage Foundation, said that if the states lose they will most likely appeal the decision to the United States Supreme Court or refile the lawsuit once the EPA finalizes the rule.

Learn more about what’s expected to be a long legal fight in the video above.