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A long-running political dispute between two American Indian tribes forced more than a century ago to live together on the same reservation has spilled into the courtroom, with one accusing the other of violating its sovereignty.

More than 10,000 Northern Arapaho and 4,000 Eastern Shoshone live on the Wind River Reservation, in a rural basin ringed by mountains. The two tribes — historic adversaries made to live side-by-side in the 1860s — for decades maintained separate governments, but have met regularly through a joint council.

Now, after the Arapaho attempted to dissolve the council two years ago, the tribe is suing two Shoshone leaders in federal court in Montana. The suit filed Monday claims Eastern Shoshone leaders unilaterally revived the joint council and approved mineral leases and made hiring decisions without consulting the Northern Arapaho.

The Arapaho also allege officials from the U.S. Bureau of Indian Affairs encouraged the Shoshone to take independent action affecting both tribes, despite the Arapaho’s objections.

“One tribe can’t run programs for another without its consent,” Northern Arapaho Business Council Chairman Dean Goggles said in a written statement.