Wynn Las Vegas LLC has gone to court to challenge the $15.7 million fee it must pay to leave as a retail customer of Nevada Power Co. and secure its own energy supply on the wholesale market.

The gaming company filed a lawsuit Thursday in Clark County District Court against the Nevada Public Utilities Commission, which is requiring Wynn and two other gaming companies to pay $126.6 million in exit fees.

“The PUC has simply made up rules as it goes along so as to discourage any applicants from exiting bundled retail service,” the lawsuit alleges.

Exit fees approved by the commission in December are $86.9 million for MGM Resorts International, $23.9 million for Las Vegas Sands Corp. and $15.7 million for Wynn, plus recurring fees and charges to recover certain costs that cannot be quantified now.

The companies’ departures are the first in many years. The hotel-casinos relied on a 2001 law approved by the Nevada Legislature allowing companies to leave as utility customers to lessen pressures on electricity rates during an energy crisis.

Circumstances behind its passage no longer exist. Instead, energy prices are increasingly competitive, including those for natural gas. Large companies that exit are expected to be able to negotiate their own favorable rates for power.