Wasn’t there just a SCOTUS case where they actually stopped the federal government from doing something because it would violate an old treaty? If so, it seems like the government’s ability to do whatever it wants in this area might get clipped.
The decision was that congress had not disestablished the reservation as part of the Oklahoma Enabling Act of 1906, and so they could not be convicted in Oklahoma courts.
This emphasizes, not diminishes, congresses role in deciding what reservations are established or not.
They could do something about it, but they need to pass a law to do it. They can't just do it without changing the law.