I worked for 2 different Tribes for a number of years. It's only as complicated as the Tribes allow. It's real simple: Sovereign Nation means Sovereign Nation. When one Sovereign Nation can tell another Sovereign Nation what to do, how to do it, when to do it, etc., then one of those Nations is not sovereign, period.
RE: Sovereign Nation” - I’ve also worked directly for two, and consulted for an even dozen others. Their attorneys have told me, without exception, that they are, with few exceptions, “Dependent nations” subject to the laws of the U S. One gave me two concrete examples: (1) Tribes cannot enter into treaties with foreign countries;, and (2) Tribes cannot issue monies that will be recognized outside their federally recognized boundaries.