Following years of delay and legal wrangling, the Department of the Interior said Monday it plans to cancel 18 natural gas and oil leases in Montana’s Lewis and Clark National Forest.

In a filing, Interior said it would initiate the process to cancel the leases as early as Dec. 11 in the Badger-Two Medicine area of the national forest, considered sacred by the Blackfeet Indian Nation in the United States and Canada. Although the leaseholds in question are in the national forest and not on Montana’s Blackfeet Reservation, the area is the site of the creation story of the four Blackfoot tribes and the Sun Dance, which is considered central to their religion.

Dozens of leases originally were sold during the 1980s to producers in the area but a federal drilling suspension has been in place nearly as long. Over the years many of leases have been surrendered or retired.

Two years ago leaseholder Solenex LLC challenged the suspension to allow it to drill for natural gas. Under an order from U.S. District Judge Richard Leon, federal officials had faced a Monday (Nov. 23) deadline to notify the court whether it would lift the drilling suspension or cancel the leases. Devon Energy Corp. still holds most of the other leases, according to federal officials.

Interior said in its filing the leases were issued without completing an environmental impact statement, which is required by the National Environmental Policy Act, and it said the leases also were not in compliance with the National Historic Preservation Act.

“Rather than undertaking a full environmental analysis before issuing the leases, the agencies attempted to defer their analysis of impacts until after the leases had been issued and an irretrievable and irreversible commitment of resources had taken place,” Interior’s filing said.

Agriculture Secretary Thomas Vilsack in early November had recommended to Interior Secretary Sally Jewell that the leases be canceled. Lifting the drilling ban would have adverse effects on the site in northwestern Montana, he wrote. Last December the U.S. Forest Service also determined that drilling would negatively impact the sacred lease site and reduce its spiritual power for the Blackfeet. The Advisory Council on Historic Preservation agreed with that finding earlier this year.

Blackfeet Nation Tribal Council Chairman Harry Barnes said Interior’s decision to cancel leases would protect a “divine sanctuary” for the tribe.

“With the Department of Interior’s decision…the government has formally acknowledged that drilling in the Badger-Two Medicine would cause devastation beyond repair,” Barnes said.