[Principled]

Reservations are sovereign territory - I don’t think the feds have shot to say there.

[Harmless Teddy Bear]

They are dependent nations. The BIA (Bossing Indians Around) has authority over them as does the federal government. In fact they are often told what they may or may not do with their land by fedgov. Since fedgov calls the shots then it is federal land.

And since BIA is part of the shut down and they can no longer "manage" those lands then it would follow that the people living there would have to leave.