You "sign up" with the sovereign tribal governments, just like any other nation. EU citizenship is worth a lot to many people, but they've still managed to find

You "sign up" with the sovereign tribal governments, just like any other nation. EU citizenship is worth a lot to many people, but they've still managed to find a system that doesn't include anyone with "some European blood". Every tribe can determine their own criteria, and while some do consider how much "Indian blood" you have, that seems to be mostly because the US government heavily promoted the idea 100 years ago: https://chicago.suntimes.com/2018/10/20/18426433/warren-ancestry-brings-attention-to-how-tribes-decide-membership https://chicago.suntimes.com/2018/10/20/18426433/warren-ance...