Just a month or so after the Blackfeet successfully defended culturally valuable places along Montana’s Rocky Mountain Front from oil and gas development, they may have to do the same once again to preserve some mountains to the east.

On Thursday, the Assistant Secretary of the Interior for Land and Minerals Management proposed extending for another 20 years an order that locks up undeveloped mineral rights on almost 20,000 acres of public land in the Sweet Grass Hills of north central Montana.