Have you gone here for info?
http://www.tribal-institute.org/lists/codes.htm
Also, just note. In most states (if not all) you are safe on a public road that
goes through the reservation that is patrolled by the state or county law enforcement agencies.
For example 191 or 160 through the Navajo Nation is ok. In fact, some of the Navajo nations in AZ allow carry with a permit.
Another example is I-40 through OK. You go in and out of Indian reservations quite often.