This is a real gray area that has not been fully tested as far as I know. Yes, reservations are their own little worlds with their own laws. That being said, the reservation I work on has their own law and order code and their own courts. However, it has been determined here that tribal law can not be enforced on non-Indians. I'm not sure how our current tribal council feels about this subject. Our previous tribal chairman had made the comments that he would have anyone carrying, whether you had a ccw or not, arrested for violation of tribal law. Now, we have an agreement that tribal police can arrest people for violations of State and local laws but they would go through the State court system. The State court system can not enforce tribal law on anybody. I once asked the county prosecutor about this. They told me that if the tribe brought a case to them where a non-indian was arrested for carrying, they would hand them their weapon back and tell them to have a good day, case dismissed for lack of jurisdiction.
Not sure how this would work out elsewhere.