Over the last two decades, utilities have closed hundreds of coal-fired power plants in favor of cheaper options like wind, solar and natural gas. The shift has cut U.S. carbon emissions and air pollution.

But since returning to office, the administration has issued emergency orders to keep eight coal units operating past their planned retirement dates, arguing that their closure would raise power bills and threaten grid stability. Environmental groups and several states have challenged the orders, saying the retirements are part of a planned transition, not a crisis.

Now, the administration is also facing pushback from two Colorado utilities, which say the federal government’s order is both unnecessary and unconstitutional.