In Oklahoma, it doesn’t go off DNA or even proven ancestry- it goes strictly off the Dawes rolls. Dawes was a man hired by the US government to make a list of all Native Americans for land grants etc. If any of your ancestors signed these rolls, you can get a CDIB card (certified degree of Indian blood) which is the only way to enroll in the tribes there. Once you are enrolled in a tribe, you are considered Native American even if you are majority white. It is not uncommon to see CDIB cardholders with 1/124th or 1/215th etc. Anyone with 1/4 or more is extremely rare and they are eligible to be elders and often get offered special jobs at the nation.