An Indian Tribe has the sovereign right to ban a non-member from its Reservation. This is subject to the restrictions imposed by the tribal constitution and statutes. If the tribe has a tribal court you would need to file the challenge in that court. Attempts at bringing cases like this in Federal Court under the Indian Civil Right Act have generally been unsuccessful. You will need an attorney experienced in Indian to help you.
This is not intended as legal advice. It is only provided for educational purposes and cannot be relied upon as legal advice. Further no attorney client relationship is or has been formed by answering this question.