PORTLAND, Ore. - The state Supreme Court has thrown out a lawsuit to block a new Indian casino on the Oregon coast, deflating the hopes of anti-casino activists who thought they had discovered a legal flaw in Oregon's tribal gaming rules.

Casino opponents had argued that the governor couldn't sign a gaming compact with a tribe because the state constitution prohibits casino gambling.

Tribes aren't subject to state law, but many have signed agreements with states to open casinos under the 1988 federal Indian Gaming Act. The agreements, which cover such issues as traffic rules and public safety, are in place in about 25 states.

The Oregon case targeted one of these agreements, following a strategy that has proved successful in other states and is gaining momentum as a legal tool for opponents of Indian gaming across the country.

Similar cases in New York, New Mexico and Kansas have been successful in blocking casinos, said Alex Johnson, a New Mexico attorney and an expert on Indian gaming law hired by the Oregon group that filed the suit.

The New York case went to the U.S. Supreme Court, but last month justices said they wouldn't get involved in Indian gaming disputes and that state courts would have to rule on the legality of such compacts.

The Oregon Supreme Court on Tuesday unanimously dismissed the legal action - a writ-of-mandamus request - without comment, court clerk John Koskela said.

The ruling, however, appeared to quash hopes of casino opponents to legally block the 400-slot Three Rivers Casino and convention center in Florence before construction is expected to begin next year.

The plans by the Confederated Tribes of the Coos, Siuslaw and Lower Umpqua Indians so angered residents in the 7,500-population tourist and resort town on the Pacific coast that the City Council voted this past spring to refuse water and sewer service to the tribe.

The tribe shot back that it would drill wells for water and build a sewage system. Dueling pro-and anti-casino signs popped up on U.S. 101 near the town.

Francis Somday, administrator of the 700-member tribe, based in Coos Bay, said many bars in Florence run mini-casinos with video lottery machines, and that state statistics show that residents are among the most prolific gamblers in the state.

The tribe considers gaming a right necessary for financial security. It hired Las Vegas-based gambling developer ROI to build and manage the 400-slot gaming floor, expected to net $10 million to $12 million a year.