Dennis Zotigh at the NMAI has a blog post asking Who is Indian, and what makes a person an Indian?
It's a moving target, I say. The rules get changed, sometimes depending on how much per capita is, or would be if they cut Indians from the tribe. From Dennis' Blog Post:
The question of who is an Indian is often debated among Indian people. Does carrying a Certificate of Degree of Indian Blood (CDIB) make you Indian? Does being raised away from a reservation and not having traditional knowledge make a person less Indian? Does knowing your language make you more Indian? These are some of the complex questions that have been debated on determining Indian identity. The response depends on who is answering the question.
Skin color does not make you Indian. In our museum I have heard non-Indians comment they have seen an Indian simply if the person they saw has the long black hair, brown skin, and high cheek bones associated with the classic Indian image. In reality, there are proud Indians with blonde hair and blue eyes or black skin. Through intermarriage, their Indian descent comes from one or both Indian parents.
Each tribe has the sovereign authority to define who its members are and who is eligible to be enrolled. Some tribes have blood quantum requirements—a requirement that to be enrolled, a person must have at least a certain degree of tribal ancestry, such as one-fourth—while other tribes’ laws state that a person is eligible for enrollment if one of his or her ancestors appears on a particular historical list of tribal members. Ultimately the question, “Who is an Indian?” is determined by tribal law
See the rest of the article HERE