New York — An attorney for MGM Resorts International argued Monday in federal appellate court that the Connecticut law that sanctioned the Mashantucket Pequot and Mohegan tribes' pursuit of a third casino in the state hampered MGM's ability to do the same thing.

Kevin King, facing a three-judge panel of the 2nd U.S. Circuit Court of Appeals, said the law, passed by the Connecticut General Assembly in 2015, granted the tribes the exclusive right to take steps that could lead to a third casino.

"You say it's exclusive; they say it isn't," Judge John Walker Jr. said.

"We think it's clear," King said.

"It isn't," Walker said. "It doesn't say 'exclusive' in it. ... It puts the thumb on the scale for the tribes, but that's not the same thing as giving them an exclusive right."

MGM is appealing U.S. District Judge Alvin Thompson’s June decision granting the state’s motion to dismiss MGM’s lawsuit, which asked that the 2015 law be invalidated.

The tribes sought the law out of concern over the impact of MGM Springfield, the $950 million resort casino now under construction in Massachusetts. When complete, it is expected to divert jobs and revenue from the tribal gaming facilities in southeastern Connecticut — Foxwoods Resort Casino and Mohegan Sun — which forward 25 percent of their slot-machine winnings to the state.

While the measure specified that the tribes could form a partnership and solicit site proposals from municipalities, it did not authorize commercial, as opposed to tribal, gaming in the state. Such authorization would require enactment of another law.

King said MGM was looking for “equal treatment,” noting that the tribes posted their request for site proposals on a state website, an option unavailable to MGM.

“It’s a vague injury, not a real injury,” Judge Robert Sack said. “It’s a signal that the rule isn’t for you.”

“It’s discrimination,” King said.

The state, whose case was argued by Assistant Attorney General Robert Deichert, maintains that the 2015 law didn't prevent MGM or any other entity from taking preliminary steps similar to those the tribes are taking.

He said the tribes derived "no appreciable advantage" from being able to post their request for proposals on a state website.

"(But) isn't it the state's stamp of approval?" Judge Denny Chin asked.

Deichert also argued that MGM had not been harmed by the 2015 law because it has not pursued a Connecticut casino and that "there's a real possibility that nothing will ever be approved" in the way of commercial gaming in the state.

"If they have no real interest, why are they paying four lawyers to sit here?" Walker asked, referring to MGM Resorts.

In fact, King said, MGM has investigated the Connecticut gaming market and has identified Bridgeport and other locations as potential casino sites. The terms of its Massachusetts casino license prohibit it from seeking another license within 50 miles of Springfield, an area that encompasses north-central Connecticut.

The tribes are considering site proposals submitted by East Hartford, East Windsor, Hartford, South Windsor and Windsor Locks, all of which are well within 50 miles of Springfield.

In a light moment, Walker suggested MGM could put a casino “right next to Yale – that would be perfect.” Walker earned his bachelor’s degree at the New Haven school.

Following the hearing, Uri Clinton, senior vice president and deputy general counsel for MGM Resorts, said MGM had presented the judges with "strong arguments." He declined to say how he thought the judges had received them.

Deichert declined to comment.

The judges did not indicate when they will issue a ruling.

b.hallenbeck@theday.com