The Seneca Nation’s plans for a bigger, more elaborate casino in downtown Buffalo got the legal go-ahead Friday when a federal judge dismissed the last of three lawsuits seeking to block the project.

Chief U.S. District Judge William M. Skretny rejected the argument that the downtown casino is illegal, ending for now an anti-casino group’s seven-year legal battle with the Senecas.

The group, Citizens Against Casino Gambling in Erie County, plans to appeal Skretny’s decision.

The Senecas, meanwhile, claimed victory after being on the losing end of two previous casino rulings by the judge.

“Many years have been spent debating these issues,” Seneca President Barry E. Snyder Sr. said in a statement. “We are one step closer to putting this behind us.”

It’s not clear what impact, if any, a federal court appeal may have on the casino project, but the Senecas are moving ahead as if they anticipate victory.

The nation is in the midst of a $130 million expansion that will replace the current slot machine-only casino that opened in 2007 with a much larger complex featuring 800 new slots, as well as table games and a small restaurant and bar.

The Senecas say the new casino, located at Michigan and South Park avenues, will open this fall and employ nearly 500 people.

Skretny, who had ruled in favor of casino opponents in two previous lawsuits, found reason to rule against them this time.

This suit, like the previous ones, argued that the Senecas do not have jurisdiction over their downtown property and, even if they did, the land is subject to a federal prohibition against gambling.

Skretny, in his ruling, pointed to a “new and critical” development regarding the federal government’s approval of the downtown casino.

Unlike the two previous suits, he concluded that the Senecas’ downtown property is “gaming eligible” because it is now clear that Congress never intended its gambling prohibitions to apply to the casino in Buffalo.

The judge specifically pointed to the National Indian Gaming Commission’s January 2009 approval of the casino.

“Apparently Judge Skretny relied on that as adequate authorization,” said Cornelius D. Murray, a lawyer for the citizens group. “We respectfully disagree.”

It was that same 2009 decision that, in fact, prompted this latest lawsuit.

The citizens group filed the suit, its third, in April of that year and argued that the Indian Gaming Commission changed the rules to benefit the Senecas and then waited until the day President Obama was sworn into office to formally sign off on the new casino.

The group also accused the commission of ignoring Congress’ intent when it approved the project in 2009.

The suit also led to new allegations that a personal relationship between a high-ranking government lawyer and a lawyer for the firm that once represented the Seneca Nation resulted in a serious conflict of interest and tainted approval of the downtown casino.

Skretny eventually ruled against the citizens group and found the lawyers’ relationship – the two are now married – did not play a role in the approval of a Seneca casino.

Friday’s ruling denied the group’s motion for summary judgment and dismissed its lawsuit.

“We’re obviously disappointed, but we think there’s several avenues of appeal,” Murray said. “A case of this magnitude and importance is not going to be decided at the district court level.”

The Senecas, in contrast, downplayed the likelihood of an appeal.

Snyder, in his statement, referred to Gov. Andrew M. Cuomo’s recent interest in casino gambling and suggested that the Senecas are not alone in believing that casinos can help boost the local economy.

“The leaders of New York State have recognized that gaming is an important element of the region’s economic recovery,” Snyder said. “The Seneca Nation looks forward to the grand opening of the new Seneca Buffalo Creek Casino.”

Skretny’s ruling came just days after Cuomo announced his intention to push for a new competing commercial casino unless the Senecas end their $600 million casino revenue-sharing dispute with the state.

The governor said he would give the nation until the third week of June to resolve the dispute.