Dennis Champlain’s grandfather helped win federal recognition for the Narragansett Indian Tribe. Later, Champlain danced in tribal powwows. He teaches his children that they are Narragansetts.

Yet the Narragansetts say he no longer is.

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. Tribal officials say they have the right to decide who’s a member and to prevent fraud from people angling for a share of gambling money. But many of those kicked out complain they have little recourse to fight what amounts to an attack on their identity.

“We’re in the process of a redefinition of tribal identity at its core,” said Dr. David Wilkins, a political scientist at the University of Minnesota and a member of North Carolina’s Lumbee Tribe. “It’s ramping up in a way that’s really quite frightening to a lot of Native people.”

Wilkins traces most purges to four factors: internal political squabbles, stricter racial requirements for membership, punishment for gang or drug-related crime and, most often, during debates over sharing casino profits.

A 1978 U.S. Supreme Court ruling said the federal government should not intervene in most tribal membership disputes, leaving appeals up to the tribes.

Tribal casinos generated $25 billion in revenue last year, according to the National Indian Gaming Commission. Tribes often split the profits by making payments to members. Fewer members can mean larger paychecks for those left.

However, paychecks can also lure people with dubious claims of ancestry. The Pechanga Band of California said it was deluged with membership claims after it opened its casino in 1995.

John Gomez Jr., 39, a Pechanga member since childhood, was kicked out in 2004. He said gambling profits were one factor: He lost free health care and a $15,000 monthly payment. But he said he and others had questioned leaders before a tribal election.