BILLINGS, Mont. (AP) — U.S. officials on Tuesday announced the cancellation of the final two oil and gas leases in a wilderness area bordering Glacier National Park that’s sacred to the Blackfoot tribes of Montana and Canada, more than three decades after the tribes said the leases were illegally sold.

Lease owners in Nebraska and Texas were notified of the cancellations in a letter from Deputy Interior Secretary Michael Connor and offered refunds of about $30,000 each.

The move is subject to a potential court challenge. A lawsuit against another lease cancellation in the area last year is pending before U.S. District Judge Richard Leon in Washington, D.C.

The undeveloped leases were issued in the 1980s in the Badger Two-Medicine area, the site of the creation story for Montana’s Blackfeet Nation and the Blackfoot tribes of Canada. Tribal members had argued that the leases were sold improperly and without due consideration of the area’s cultural significance.

Blackfeet Tribal Chairman Harry Barnes said his people were grateful for the cancellation.

“This area is like a church to our people,” Barnes said. “We’ve lived for 30 years under the threat that it might be industrialized.”

The leases cancelled Tuesday were held by W.A. Moncrief with Moncrief Oil and Montex Drilling of Fort Worth, Texas, and the J.G Kluthe Trust of Elgin, Nebraska.

The cancellations were not voluntary, and it was uncertain if the owners planned to challenge them, said Alyse Backus, a spokeswoman for the Interior Department’s Bureau of Land Management

Representatives of Moncrief and the Kluthe trust did not immediately respond to telephone messages left by The Associated Press seeking comment.

The Badger-Two Medicine area is part of the Rocky Mountain Front, a scenic expanse of forested mountains that’s been subject to a long campaign to block oil and gas development and mining.

Congress in 2006 provided tax breaks and other incentives that prompted 29 lease holders to relinquish their drilling rights, but some leaseholders declined the offers.

In November, fifteen leases in the area were given up voluntarily by Devon Energy.

Still, the possibility lingers of limited drilling in the Badger-Two Medicine area. Another lease, cancelled in March and now subject to the pending court challenge, was held by Solenex LLC of Baton Rouge, Louisiana.

Solenex still wants to drill and is represented by the Mountain States Legal Foundation, a conservative property rights law firm. It says the lease was issued properly and that federal officials for decades have unfairly delayed attempts to drill.

An attorney for several conservation groups that have intervened in the litigation said the company’s arguments are not supported by U.S. Supreme Court decisions in similar cases.

“The case is strong that the government has the authority to cancel the lease,” said Tim Preso with Earthjustice in Bozeman.