A lawsuit against Gov. Jerry Brown that challenges the legal status of the Federated Indians of Graton Rancheria's reservation outside Rohnert Park has been set for a summer trial in Sonoma County.

The lawsuit aims to overturn a 2012 agreement between the state and the Graton Rancheria that allows the tribe to run a Las Vegas-style casino on its Wilfred Avenue property. The 3,000-slot-machine casino is under construction and set to open late this year after a decade of fierce opposition.

The lawsuit argues that the state never gave up its sovereignty over the property and that therefore, in negotiating the agreement with the tribe, Brown violated state law prohibiting casinos from operating anywhere but on sovereign tribal territory.

Stephen Pevar, senior staff counsel for the American Civil Liberties Union and author of "The Rights of Indians and Tribes," on Wednesday called the lawsuit a "very desperate and unmeritorious claim."

But Chip Worthington, a Rohnert Park pastor who leads a group that is a plaintiff in the lawsuit, said it "could be a landmark case" that could stop the casino from opening.

Sonoma County Superior Court Judge Elliot Daum on Tuesday denied the state's request to move the case to federal court — where the government might more effectively argue that it is immune from such lawsuits — and he set an Aug. 2 trial date.

On Wednesday, the Secretary of the Interior and the chairwoman of the National Indian Gaming Commission were removed from the suit. That further limits the chances that the state could get Daum to move the case to federal courts.

"This is a huge victory for us. We've gotten past the procedural hurdles," said Worthington, who heads Stop the Casino 101 Coalition, the lead plaintiff in the lawsuit.

The state Attorney General's Office referred questions about the case to the governor's office, which declined to comment.

A trial means the Stop the Casino 101's legal arguments will get a legitimate hearing, said attorney Mike Healy, who wrote the lawsuit.

"We will probably get a decision on the merits, on the substantive law, which is what we have been seeking," said Healy, who is a Petaluma City Council member.

The tribe, backed by Station Casinos of Las Vegas, bought the Wilfred Avenue property in 2005 with the express intent of having it taken into trust so that it could open a casino there. The Bureau of Indian Affairs took it into trust in 2010, a step that made it a reservation that is for the most part free of state jurisdiction.

But the lawsuit argues that the land was not historically Indian-owned, and that simply because the federal government took it into trust for the tribe does not mean the state no longer has sovereign status over the 254 acres of land. The state would lose such sovereignty only if the state agreed to cede it, the suit argues.

Some federal Indian law attorneys have characterized the suit as well-constructed with a novel argument. But none has said it has much chance of success in an arena where federal law on Indian trust land issues and sovereignty is long established, as is as federal primacy over Indian tribes and affairs.

"In terms of tribal sovereignty and in terms of placing land in trust for the benefit of an Indian tribe, it is a supremacy question," said Joseph Wiseman, who teaches federal Indian law at Empire College of Law.

"Federal law is supreme and governs the issue," Wiseman said. "As long as the Secretary of Interior through the Bureau of Indian Affairs agreed with the acquisition of that property and agreed to place the property in trust for the benefit of the tribe, it's the end of the story."

Wiseman is a judge on the Dry Creek Rancheria Band of Pomo Indians tribal court but emphasized that he was not speaking in that capacity.

The Stop the Casino 101 lawsuit's arguments are based partly on a 2004 case in which a federal court ruled that Inyo County was able to tax an energy company that did business on land the United States had owned before California became a state.

The court ruled that although the United States had owned the land, part of the China Lake Naval Weapons Station, continuously since before California's statehood, the state still had never ceded its sovereignty over the land.

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