In the USA, indigenous people have a pretty distinct definition based on being a certified or enrolled member of a Federally recognized tribal organization. Of course people can call themselves whatever they like, but that doesn’t mean that others who are members of the group they aspire to have to accept them as such. Individual tribes determine membership qualifications and thus a person’s legal status as “indigenous” or not, and why shouldn’t they? I’ve always considered myself an Iroquois warrior at heart, and that and $5.95 will buy me a pack of Indian cigarettes at the Pow-Wow.