OK, since I live in Wyoming and am reasonably close to the Crow Reservation, I’m going to dispel some myths for people here.
1. You should NEVER assume that state law applies on a res. NEVER. The reservations are their own sovereign nations, and they are not bound to recognize state laws except where they agree to do so. Getting pulled over and whipping out a CCW issued by a state (whether MT or another state) when you’re on a back road or reservation property might not get you the results you want . . .