Actually I would have expected a trademark. An Indian tribe name could be trademarked as a sports team trademark. But the tribe would have to file for the trademark before it was used. Some savvy tribes do, for example the Seminole (and they rake in the dough and both the Injuns and the palefaces are happy). But the Indian tribes can’t come along decades later and pull a stunt like this.
That said, there is no one fixed opinion in Indiandom about the suitability of paleface sports teams borrowing their tribe names. Some love it, some hate it, some don’t care.
A stunt like what? The tribe is suing the NCAA to STOP them from telling UND that they have to drop the Fighting Sioux name.