WASHINGTON – The Tule River Indian tribe runs a booming casino with 1,500 slot machines on its reservation in central California. But the casino is up a long, winding road, and tribal members are eyeing a better location along Highway 190.

In search of bigger crowds and greater profits, Tule River is one of many tribes pushing toward what some say will be Indian gambling’s next frontier: off-reservation casinos.

“It is like any real estate. What are the three rules? Location, location, location,” said Tom Rodgers, a member of the Blackfeet tribe in Montana and a consultant to Tule River and other tribes. “Access to market is everything now.”

The trend is being watched warily by some federal officials and local residents.

“When we voted for Proposition 1A, that was to help the Indians gain self-sufficiency,” said opponent Robert Inabinette, referring to an American Indian gambling ballot measure approved by California voters. “We didn’t in our wildest imagination ever think that they’d want to move off the reservation and put in a Vegas-style casino.”

Tribal gambling has boomed since Congress legalized Nevada-style Indian casinos 16 years ago. Some 377 tribal casinos nationwide brought in about $15.9 billion in revenue in 2003, easily eclipsing the $9.6 billion rung in by Nevada’s gambling industry. The largest tribal casinos, the Mohegan Sun and Foxwoods Resort in Connecticut, are huge resorts boasting more than 6,000 slot machines each – three times as many as the average Las Vegas strip casino.

But some tribes have prospered more than others. Many are hampered by reservations in remote rural sites, and some of these tribes are trying to move to better locations – even if they’re far from the reservation land where most agree federal law intended tribal gambling to occur.

“The Indian Gaming Regulatory Act was set up to disfavor off-reservation casinos,” said Washington attorney Guy Martin, whose firm represents communities in tribal disputes around the country. “Still and all, off-reservation casinos are clearly the most desirable locations, and since almost every tribal casino proposal exists because of the participation of wealthy financial interests, that will become the main battleground of the future with respect to Indian casinos.”

The 1988 law confines tribal gambling to Indian lands, which most often means existing reservations, and prohibits gambling on land acquired after the law was enacted. But there are several exceptions, including one for land restored to a tribe that has regained federal recognition. The Interior Department also can determine that an off-reservation casino is in a tribe’s best interest and wouldn’t harm the surrounding community, if the governor of the state where the casino will be built agrees.

Fewer than 20 tribes nationwide have gotten permission for off-reservation casinos under any of these exceptions, said George Skibine, director of the Bureau of Indian Affairs’ Office of Indian Gaming Management. With 567 federally recognized tribes nationwide, tribal members cite the small numbers as evidence that off-reservation gambling is in no danger of becoming widespread.

But Skibine and others said the number of tribes trying to build off-reservation is growing.

The exact number is impossible to know because many tribes begin the process without contacting government officials. But about a dozen tribes are far enough along to have submitted environmental studies to the Bureau of Indian Affairs, and many more are in earlier stages of exploring off-reservation casinos, experts said.

In April, authorities shut down a Kansas City, Kan., casino operated by the Wyandotte Nation of Oklahoma after the National Indian Gaming Commission ruled that the off-reservation casino was operating illegally.

The Eastern Pequot Tribe of Connecticut, which gained federal recognition in 2002, sparked opposition from a leader of another Connecticut tribe with its plans for an off-reservation casino.

In Louisiana, the Jena Band of Choctaw Indians’ bid to build an off-reservation casino was approved by the federal government but not yet by Gov. Kathleen Blanco.

Interior Secretary Gale Norton weighed in against off-reservation casinos in late 2002 when she refused to sign a compact between the Seneca Nation and the state of New York allowing the tribe to build off-reservation.

“While I do not intend to signal an absolute bar on off-reservation gaming, I am extremely concerned that the principles underlying the enactment of [the Indian gaming law] are being stretched in ways Congress never imagined when enacting IGRA,” Norton wrote in allowing the compact to take effect without her signature.

To some tribe members, it’s simply unfair that they’re prevented from developing their businesses beyond reservation land.

“To me, it’s borderline racist that any other business is able to expand and it’s not questioned,” said Dave Nenna, Tule River’s tribal administrator. “But when it comes to a tribal entity, it’s, ‘Let’s suppress them and keep them on their reservation.'”