Well, there are those pesky treaties that our Government signed with the tribes. Ones that said this land is yours as long as the sun shines and grasses grow.
The tribes used those signed treaties to gain sovereignty into what they are now. I live on the Osage Rez and am already subject to the tribal rules and regulations even though I don't claim any Native heritage with the Osage tribe.
Treaties are agreements, they're only good as long as both parties agree to them.
If we're going by pesky treaties, most of those were signed under dubious circumstances and in many cases the opposite parties weren't exactly the appropriate authorities representing all the natives subject to the conditions therein. In other words, most the treaties we wrote with the Native Americans aren't legitimate anyway.
This is the United States. Not the Iroqois Confederacy, Osage, Cherokee or whatever. We are one nation, one people and we all follow the supreme law of the land, the Constitution of the United States. i recognize no other legitimate authority, because there isn't any.