After a week on the sidelines, MGM Resorts International jumped back into Connecticut’s casino fray Wednesday, lodging a new lawsuit over the U.S. Department of the Interior’s approval of the Mashantucket Pequot and Mohegan tribes’ pursuit of a commercial casino on nontribal land in East Windsor.

The suit, filed in U.S. District Court in Washington, D.C., claims amended gaming agreements between the tribes and the state are unprecedented and illegal and put MGM at a competitive disadvantage in bidding to operate a commercial casino in the state.

“Interior’s approval decisions establish an unlawful state-conferred monopoly over commercial gaming rights in Connecticut,” MGM Resorts said in a statement. “These decisions also stand in the way of an open, competitive process that MGM believes would result in a better deal for the people of Connecticut. An open process would allow the state to evaluate competing proposals and choose the operator that offers the best investment opportunity, creates the most new jobs and economic expansion and maximizes revenue to the state."

MGM had remained uncharacteristically silent in the face of state lawmakers’ proposal last week to grant the tribes the right to operate a Bridgeport casino and provide online gaming and sports betting at their existing casinos, Foxwoods and Mohegan Sun. The proposal would allow the tribes to proceed with their East Windsor project, too.

Days ago, a plan to have the tribes operate gaming at the XL Center in Hartford surfaced.

Gov. Ned Lamont has urged the tribes to abandon East Windsor, fearing MGM was bound to renew litigation aimed at stopping it. The East Windsor casino site is 12 miles south of MGM Springfield, the Massachusetts casino MGM Resorts opened a year ago.

“As I have consistently said, our state needs to reach a global gaming resolution that will avoid years and years of complex litigation,” Lamont said in a statement Wednesday. "The gaming industry in Connecticut represents a significant portion of our economy, and as other states have demonstrated, there is room to grow it. It has always been my intention to develop a comprehensive gaming platform that not only strengthened Connecticut’s gaming industry, but protected it from litigation. Our administration remains committed to these objectives and looks forward to working toward a solution that moves the state forward with the General Assembly.”

The tribes, who have battled MGM Resorts since forming a joint venture, MMCT, to pursue the East Windsor project, also anticipated more litigation.

“MGM pursues litigation because that's what MGM does,” Andrew Doba, an MMCT spokesman, said Wednesday. “Remember, this is the same company that sued the victims of a mass shooting to cover their liability. We should also all remember the last time MGM waded into the DC swamp it resulted in multiple investigations, the convening of a grand jury and the resignation of a cabinet secretary.”

Doba was referencing victims of a 2017 incident in which a gunman fired on a crowd from an MGM casino in Las Vegas, and MGM’s efforts to influence Interior’s handling of the tribes’ gaming amendments. Former Interior Secretary Ryan Zinke resigned amid the controversy.

While advocating for the state to adopt a competitive-bidding process, MGM proposed building a casino in Bridgeport. The tribes’ existing casinos, located on their respective southeastern Connecticut reservations, are considered “tribal” rather than “commercial” and are subject to the provisions of the federal Indian Gaming Regulatory Act rather than regulation by the state.

“These amendments have the stated purpose of facilitating off-reservation, commercial gaming operated by a joint venture wholly owned by Indian tribes,” MGM’s suit says. “These amendments therefore circumvent IGRA’s land-in-trust process, which governs off-reservation gaming, and allow Connecticut’s federally recognized Indian tribes to leverage their duopoly over tribal gaming to obtain a monopoly on commercial gaming in Connecticut.”

The suit says no other state has “implemented a hybrid commercial-tribal scheme similar to Connecticut’s.”

The recent legislative proposal granting MMCT the right to operate a Bridgeport casino “doubles down on Interior’s errors rather than learning from them ...,” MGM said in its statement. “Like the East Windsor proposal, the new Bridgeport bill relies on the Interior Department’s unlawful approval decisions and could not function without them.”

A tribe-owned casino in Bridgeport would subject MGM’s Empire City Casino in Yonkers, N.Y., less than 50 miles from Bridgeport, to “additional competition,” the suit says.

In 2017, the tribes and the state sued Interior and then-Secretary Zinke in a bid to compel action on their amended gaming agreements. Ultimately, the suit became moot when Interior “deemed approved” the Mohegans’ amendment in May 2018 and, finally, approved the Mashantuckets’ amendments in March of this year.

MGM, in its suit, claims Interior provided no explanation for reversing course and approving the amendments, originally having returned them to the tribes because of “insufficient information.”

b.hallenbeck@theday.com