See link for full article, focusing on Narragansett Indians in Rhode Island, but also discussing other Indian tribes who have recently been purging members from tribal lists.
Quotes from article:
Champlain and his extended family are among thousands of people removed from American Indian tribes in recent years, often amid tribal squabbles or when a casino comes to town. In Rhode Island, the Narragansetts' removal of about 140 of roughly 2,400 members has become an issue in Saturday's election for the tribe's chief sachem, or leader. . . .
There are 562 federally recognized tribes, and tribal governments are not required to report citizenship decisions. But the number is in the thousands.