In the latest example of overreach from activists at the Environmental Protection Agency, the EPA ruled that roughly a million acres near Riverton, Wyoming is no longer part of the state. Instead, the EPA says that land belongs to the Wind River Indian Reservation.

Congress passed a law in 1905 opening that land up to settlement, but the EPA took it upon itself to determine that Congress didn’t actually intend to distinguish the land’s reservation status. The EPA involved itself in the drawing of state boundary lines after the Indians on the reservation applied to be considered a separate state under the Clean Air Act.

Wyoming isn’t amused. Attorney General Peter Michael wrote:

EPA not only reached the wrong conclusion, but the agency also employed a fundamentally unfair and skewed process, to the detriment of the state and its citizens, in pursuit of its predetermined objective.

Wyoming has appealed the EPA’s ruling—federal courts are expected to have the final say in whether the agency’s surprising move will stand.