A Sonoma County judge on Thursday dealt a serious blow to opponents of the tribal casino being built outside Rohnert Park, tossing out a lawsuit aimed at halting the project that had been set for trial today.

The lawsuit filed against Gov. Jerry Brown was the latest effort in a 10-year battle by the Stop the Casino 101 Coalition to derail the casino being developed by the Federated Indians of Graton Rancheria. It sought to invalidate Brown's contract with the tribe that allowed it to build a Las Vegas-style casino on its 254-acre Wilfred Avenue reservation. Casino foes had hoped a successful suit would limit the tribe to a gambling hall with only bingo machines and card games, perhaps crippling a project that has cost $800 million to develop.

As it stands, the Graton Resort & Casino is set to open late this year as the Bay Area's largest gaming hall, with 2,000 employees and 3,000 slot machines.

Following the ruling, Stop the Casino leaders immediately announced they would consider appealing the decision. They suggested that Superior Court Judge Elliot Daum had been wary of tackling a case involving the extraordinarily complex area of Indian law, one that could have reverberated broadly in the world of tribal casino development.

"I did really feel that this would be a tough case for a local judge because of the magnitude of the case," said Marilee Montgomery of Rohnert Park, one of the plaintiffs.

The lawsuit's central argument hinged on the fact that California has never formally ceded the land that makes up the tribe's reservation to the federal government, which took the property into trust for the tribe in 2010.

Without that action, the property remained under the control of state law, the lawsuit said, which would mean that Nevada-style gaming is illegal there and that Brown's agreement with the tribe violated the state Constitution.

Daum, in a 14-page ruling, agreed that the state had never ceded jurisdiction over the tribe's land; that the land, before it was taken into trust, had never since California's statehood been governed by the Graton Rancheria; and that the 2000 congressional act that restored the tribe's federally recognized status does not "purport to alter California's sovereignty or jurisdiction over the property."

But he cited previous court cases to rule the lawsuit's argument invalid. He noted a similar claim by the city of Roseville against the United Auburn Indian Community, which runs the Thunder Valley Casino Resort. A federal court dismissed that case in 2002.

The Roseville case, he said, "negates plaintiffs' claim that the property on which the tribe is building its casino must be ceded by the state to the federal government to be eligible for gaming."

He also said the lawsuit did not question the federal secretary of the Interior's act of taking the Graton Rancheria property into trust, and it did not challenge key tenets of federal Indian gaming law.

Those tenets included that the 1988 Indian Gaming Regulatory Act, or IGRA, allows Las Vegas-style gambling on lands under Indian jurisdiction, and that it specifically allows gambling to take place on lands taken into trust after 1988 for tribes that were federally restored as recognized Indian nations, as was the case with the Graton Rancheria in 2000.

"Plaintiffs effectively concede all the elements necessary to establish the validity of the compact (the tribe's agreement with the state) under federal law," Daum wrote.

But Mike Healy, the Petaluma councilman who was a lead attorney in the case for the plaintiffs, said Daum had "conflated" two different legal points.

While the tribe clearly had been restored and became eligible to run a casino on sovereign lands, Healy said, "that only gets you halfway there."

The law allowing restored tribes such as the Graton Rancheria to have a gambling operation on lands purchased and taken into trust to be "restored" after 1988 does not provide an exception to the law that Las Vegas-style casinos can be run only on land that tribes have jurisdiction over, he said.

In the case of the Graton Rancheria, it did not have that sovereign jurisdiction over the Wilfred Avenue property, Healy said, because the state never ceded it to the federal government.

Without that action, Healy said, the secretary of the Interior's act of taking the land into trust, while establishing the land as a reservation, did not make the tribe sovereign over it.

He said it was too early to know whether he would recommend an appeal.

"The legal team on our side is going to want to take some time to read (the ruling) closely," he said.

Montgomery, the plaintiff with Stop the Casino 101, said, though, that the sentiment is that it would be fruitful to appeal. "We've always felt really strongly that this is a good case for the higher courts. So we think we can take this to the state appeals court or even the state Supreme Court," she said.

Neither Graton Rancheria attorneys nor the state responded to requests for comment.

One Indian law expert said an appeal might be a tough avenue to go down. Attorney George Forman of San Rafael said he has yet to read the ruling, "but speaking generally, from my experience, I would say the likelihood of a court of appeal reversing that is fairly low."

Similar challenges to Indian sovereignty have been made before, both in relation to gambling and other matters, such as fishing rights, he said, "and all those attacks have failed."

When the Wilfred Avenue property was taken into trust, Forman said, "it became Indian country and is subject to the sovereign rule of the Federated Indians of the Graton Rancheria, subject to the overall power of the United States."

You can reach Staff Writer Jeremy Hay at 521-5212 or jeremy.hay@pressdemocrat.com.