If it’s DNA, then that’s pretty clear. As far as the Cherokee “we gotta agree you’re in our tribe” stuff, that’s just impediment to keep from having to share the gambling wealth, IMO.
The problem with DNA is that the marker used for Amercan Indians is Asian. That’s why many Germans test 2% Indian, which has more to do with the Mongol invasion.
I think a lot of people were surprised when their DNA results showed Indian ancestry.