https://www.scconline.com/blog/post/2016/06/21/use-of-prior-tribal-court-convictions-consistent-with-the-indian-civil-rights-act-as-predicate-offenses-for-federal-offenses-does-not-violate-the-constitution/
Use of prior tribal-court convictions consistent with the Indian Civil Rights Act as predicate offenses for federal offenses does not violate the Constitution