RICHMOND, Va. (AP) — The Virginia Supreme Court is set to hold a hearing on whether a law temporarily banning state regulators from adjusting a portion of electric rates is constitutional.

A group of large industrial electric customers is challenging the 2015 law, which critics have called a costly giveaway to electric monopolies Dominion Resources and Appalachian Power.

The law is costing a typical Dominion residential customer an extra $68 a year on their bill, according to one group’s calculations.

Supporters of the law say it has helped shield the state from potential rate spikes due to uncertainty around carbon regulations.

Opponents of the law, including former Virginia Attorney General Ken Cuccinelli, are planning a news conference after the Friday morning court hearing.