Tribal relations among mixed-race Indigenous people in the United States are governed according to a series of rights first created through federal laws and policies, then later adopted by individual tribal nations. Tribal nations now have the right to manage their own membership laws and policies, with each tribe setting its own blood quantum rules for membership. Blood quantum refers to a genealogical relationship to one’s original tribal people. Full-blooded Native people issue from parents who are both full-blooded members of a tribe, while half-blooded Native people have parents or grandparents who have at least 50 percent Native blood. A person can even be a full-blooded Native, with parents from two tribes, but be considered half-blooded by the tribe they are enrolled in because the tribe only acknowledges the Indigenous blood from the enrollment tribe (Ellinghaus 2017). Some of the terms for people of mixed heritage in the Americas are mestizo (common in Latin America) and Métis (common in Canada). Some nations, such as Canada, assign different rights to people of mixed Indigenous heritage; Métis communities are accorded different rights from First Nations communities. Although Indigenous heritage is preferred in most Native communities, the rate of outmarriage is such that pure Indigenous bloodlines are becoming rare. In the United States, most Native people have mixed heritage. An exception is the Navajo Nation, which has a significant number of full-blooded Navajo members due to its large population of more than 300,000 members. Normally, individuals have to prove they have a blood quantum of a certain percentage to enroll in a tribe. Some tribal policies require a strict accounting of only the bloodlines that originate within that tribe. Other tribes allow for any Indigenous blood as counting toward membership requirements. The latter policy is closer to the cultural practices followed by many Native peoples before they became wards of the federal government. It was common for many tribes to adopt people who moved into their area and took up their culture. In addition, marriage customs of all tribes, which disallowed marriage between individuals too closely related, encouraged members to marry outside of their village or tribe. Spouses brought into a village would be adopted without discrimination. In tribes in Oregon, women would more commonly go to their husbands’ villages. In other cultures, such as that of the Seneca of the Northeast, men would move to their wives’ villages. Some scholars view blood quantum as a means for the United States government to prevent people from claiming tribal heritage, ultimately causing tribes to self-terminate. This view is not shared by all tribal peoples. Blood quantum was written into most tribal constitutions in the 1930s as a means of determining tribal citizenships. This policy has caused numerous problems in contemporary communities, where tribal members sometimes attempt to marry their cousins in order to “marshal” their blood—that is, raise or maintain the percentage of blood quantum in their offspring (Nenemay 2005). Scholars have noted that most tribes will continue to lose members due to outmarriage unless membership requirements are changed, even though most blood quantum requirements are currently well below one-half. Many tribal communities are shifting policies so that individuals can claim tribal membership by establishing descent from an enrolled tribal member (Thornton 1997). Membership in the Grand Ronde tribe of Oregon requires a 1/16 blood quantum of Grand Ronde blood and an ancestor or parent who was on a tribal roll or record in the past. The tribe counts only genealogical connection to original tribal residents of the reservation. Unfortunately, many people have moved on and off the reservation over the years, and records have not been accurately maintained. Proving past residence on the reservation is difficult. In addition, more restrictive changes to the membership requirements since 1999 have reduced the number of members. One controversial change made in 1999 requires that the parent of a potential new member must have been enrolled in the tribe at the time of the prospective member’s birth. This change denies membership to the children of those who became members after having children and the children of those born during the period between 1956 and 1983, when tribal rolls were not maintained. One result has been split families, in which younger children born when their parents were on the tribal roll are deemed members, while their older siblings are not eligible for enrollment. The issue has become politicized at the reservation, with some enrolled members fearing that a flood of new enrollments would impact services and funds and others wanting to expand enrollment to allow more descendants into the tribe. These questions of identity, both political and social, will likely continue to excite debate in the coming decades, as many tribes acknowledge that unless they change membership requirements, they may cease to exist in the future.