I have been there and if you come from the north (from Montana) south on I-25 you pass through the Crow Reservation. If you get off the freeway you are on the reservation. The Battlefield is not on the reservation though. However, I agree. Lock the gun in the trunk. I live next door to the Nisqually Reservation. They have their own laws.If I want to fish there I have to get a permit from them. You can pass through but if you stop at the Redwind Casino, you are on the reservation. I don't know if they have a reciprocal agreement with the state or county but why risk it? Same applies elsewhere. Either call ahead and find out or lock the gun in the trunk.