Respectfully, there are a great many people who identify as "Indigenous," and most certainly have the provable roots, but cannot claim any specific nation. Some were disenfranchised by the government; others were disenfranchised by their own people for one reason or another.

That does not make those people less Indigenous. It just makes them stateless, and honestly, your comment is precisely why this kind of social violence continues to take place, both against and among Indigenous peoples.

Ethnic nationalism is highly toxic. The worst thing that could happen--and it has, and still is happening--is that Indigenous communities adopt the concepts of the oppressor. Prior to colonization, Indigenous identities were highly fluid. This idea that one had to be a documented member of a band is new, and a reflection of colonial attitudes.