COARSEGOLD, Calif. » The six-page, single-spaced letter that Nancy Dondero and about 50 of her relatives received last month was generously salted with legal citations and footnotes. But its bottom line was brutally simple. "It is the decision by a majority of the Tribal Council," the letter said, "that you are hereby disenrolled."

And with that, Dondero’s official membership in the Picayune Rancheria of the Chukchansi Indians, the cultural identity card she had carried all her life, summarily ended.

"That’s it," Dondero, 58, said. "We’re tribeless."

Dondero and her clan have joined thousands of Indians in California who have been kicked out of their tribes in recent years for the crime of not being of the proper bloodline.

For centuries, American Indian tribes have banished people as punishment for serious offenses. But only in recent years, experts say, have they begun routinely disenrolling Indians deemed inauthentic members of a group. And California, with dozens of tiny tribes that were decimated, scattered and then reformed, often out of ethnically mixed Indians, is the national hotbed of the trend.

Clan rivalries and political squabbles are often triggers for disenrollment, but critics say one factor above all has driven the trend: casino gambling. The state has more than 60 Indian casinos that took in nearly $7 billion last year, the most of any state, according to the Indian Gaming Commission.

For Indians who lose membership in a tribe, the financial impact can be huge. Some small tribes with casinos pay members monthly checks of $15,000 or more out of gambling profits. Many provide housing allowances and college scholarships. Children who are disenrolled can lose access to tribal schools.

The money and the immense power it has conferred on tribes that had endured grinding poverty for decades has enticed many tribal governments to consolidate control over their gambling enterprises by trimming membership rolls, critics and independent analysts say.

"Sometimes it is political vendettas or family feuds that have gotten out of hand," said David Wilkins, a Lumbee Indian and professor of American Indian Studies at the University of Minnesota who has studied disenrollment across the country. "But in California, it seems more often than not that gaming revenue is the precipitating factor."

At least 2,500 Indians have been disenrolled by at least two dozen California tribes in the past decade, according to estimates by Indian advocates and academics. In almost all of those cases, tribal governments — exercising authority granted by the federal government — have determined that the ousted Indians did not have the proper ancestry.

Tribal governments universally deny that greed or power is motivating disenrollment, saying that they are simply upholding membership rules established in their constitutions. To that end, they often say they are removing people with little connection to their tribe, who joined mainly for services, scholarships and monthly checks financed by casino profits.

"You have people who want to be tribal members, where no one knows who they are or where they came from," said Reggie Lewis, chairman of the Chukchansi Tribal Council. "We are sworn to uphold the constitution. And basically that’s what we try to do."

The tribe has disenrolled more than 400 members in the past five years, and scores more are facing disenrollment hearings. Some members estimate the tribe’s membership is now below 1,000.

Sometimes, disenrolled Indians are forced to leave tribal land — though in California, many Indians do not live on the small reservations, which are also known as rancherias.

The Chukchansi tribe, whose 2,000-slot-machine casino is nestled in the Sierra Nevada foothills near Yosemite National Park, gives members a monthly stipend of less than $300 per person. But it also pays for utilities, food bills and tuition — and Nikah Dondero, Nancy Dondero’s 32-year-old daughter, had to turn down a master’s degree program after she was disenrolled last month, because she lost her scholarship.

"It’s like I’m now a white girl with Okie kids," said Nancy Dondero, a mother of two.

Beyond benefits, critics of disenrollment say it can be psychologically devastating. "It destroys their connection to their ancestors, their cultural heritage, their tradition," said Laura Wass, the central California director for the American Indian Movement, an opponent of disenrollment. "You have to go to iron gates and beg for entrance to your own land."

The fights over enrollment have bred a cottage industry for ancestry research. Many tribal governments now retain lawyers or researchers who comb through government archives for evidence of an individual’s tribal authenticity. Companies that test Indian DNA have sprouted up around the country. The Chukchansi hired a former Bureau of Indian Affairs official with expertise in federal records to review the bloodline of every member.

In the case of Nancy Dondero, the disenrollment of her extended family came down to a single ancestor: a great grandfather, Jack Roan, who died in 1942 at age 76. The tribe’s enrollment committee, appointed by the seven-member Tribal Council, determined Roan was not Chukchansi based on a will and personal affidavits in which he declared himself to be a member of another tribe.

At a hearing in September, the Roan descendants were allowed to present their own evidence, which included census and land records listing Roan as a Chukchansi. But the council rejected their argument, saying their documents included incorrect information submitted by white people. Roan was removed, and so were his descendants.

Paradoxically, Roan’s face has become an iconic image of the Chukchansi, thanks to a photograph taken by Edward S. Curtis, the renowned documenter of the American West, who listed him as Chukchansi in a photograph taken in the 1920s.

One of Roan’s daughters, Ruby Cordero, is also considered a cultural pillar of the tribe because she is expert at basket weaving and among the last native speakers of the Chukchansi language. But at 87, she, too, has been disenrolled.

"She was born and raised on that property," said Nancy Dondero, Ruby’s great niece.

Disenrollments are not appealable. But in early November, the Chukchansi held tribal elections, which could result in new council members. (The vote is still being tallied.) If so, a different council could reinstate the Roan descendant, though that is far from certain.

Some Indian advocates like Wass say it is time for Congress to empower the federal courts or the Bureau of Indian Affairs to provide legal recourse to Indians who feel they have been disenrolled improperly.

Tony Cohen, a lawyer in Northern California who has represented Indians and tribal officials for three decades, said Congress could, for instance, enact legislation allowing Indians to sue tribal governments in federal court if they thought their rights were violated. But there is no such legislation pending, and Congress has shown little appetite for interfering in tribal membership issues.

"I don’t like seeing Congress interfere with Indian sovereignty," Cohen said. "But I also don’t like seeing tribal governments allowed to be, in essence, dictators."

Citing a 1978 U.S. Supreme Court decision written by Justice Thurgood Marshall, the Bureau of Indian Affairs says that tribal governments have sole authority to determine membership — unless a tribal constitution allows intervention by the government. But such provisions are rare.

And some federal officials say that is exactly how it should be.

"The tribe has historically had the ability to remove people," said Kevin Bearquiver, the bureau’s deputy director for the Pacific region. "Tolerance is a European thing brought to the country. We never tolerated things. We turned our back on people."

© 2011 The New York Times Company