In challenging the Connecticut law governing the Mashantucket Pequot and Mohegan tribes’ joint pursuit of a third Connecticut casino, MGM Resorts International wrongly concluded that the law bars it from the same pursuit, the state argued Wednesday in seeking dismissal of a lawsuit filed in August.

The suit was aimed at keeping the tribes from opening a north-central Connecticut casino to compete with the $800 million resort casino MGM is building in Springfield, Mass.

Assistant Attorney General Robert Deichert, in a motion filed in U.S. District Court in New Haven, disputed MGM’s claim that the law — Special Act 15-7 — grants the tribes the exclusive right to pursue a third Connecticut casino and is therefore unconstitutional.

“But SA 15-7 in no way excludes MGM from moving forward with developing a casino in Connecticut,” Deichert wrote. “To the contrary, MGM alleges that it has taken steps toward such a casino, and nothing in SA 15-7 precludes MGM from taking whatever additional steps it would like to take.”

The motion notes, however, that MGM’s Massachusetts-issued gaming license contains a restriction that would prevent it from developing a casino within 50 miles of Springfield.

That “radius restriction” covers all of Hartford, Tolland and Windham counties, large parts of Litchfield, New Haven and Middlesex counties and much of New London County, Deichert wrote.

Despite the restriction, MGM claims to have done a feasibility study that found that having casinos in Springfield and Connecticut would be “commercially attractive.”

In its lawsuit, MGM said the Connecticut secretary of the state had rejected its attempt to register a “tribal business entity,” one of several required steps outlined in SA 15-7.

“MGM makes conclusory allegations that the Act also precludes MGM from issuing a RFP, engaging in negotiations with municipalities and signing development agreements with them and claims time is of the essence,” the motion says. “More importantly for present purposes, MGM points to no state law or language in SA 15-7 precluding entities other than the tribal business entity from taking those steps."

The motion goes on to argue that MGM misread SA 15-7.

The law "imposes specific obligations on the Tribes — not MGM — and leaves MGM free to pursue whatever plans it may have to develop a Connecticut casino,” the motion says.

The Mashantuckets and Mohegans signed an agreement establishing a business entity earlier this month. The entity, MM4CT Venture, will sift proposals it expects to receive from municipalities willing to host a casino. East Hartford, East Windsor and Enfield are among the north-central towns expected to generate proposals.

Even if it reaches an agreement with a municipality, “the tribal entity still has no guarantee that it will be able to actually operate a casino,” Deichert wrote, since the tribes would still have to persuade the state legislature to adopt a law allowing a third casino in Connecticut.

“MGM is free to create a business entity (just not a tribal business entity), register it with the Secretary of the State, issue a RFP, negotiate a development agreement with a municipality and ask the state to make the changes to the law that would be necessary for the agreement to be approved. ...,” the motion says.

MGM’s suit named as defendants Gov. Dannel P. Malloy, state Secretary of the State Denise Merrill and Department of Consumer Protection Commissioner Jonathan Harris. The state’s motion says the 11th Amendment of the U.S. Constitution bars the claims against the governor.

b.hallenbeck@theday.com

Twitter: @bjhallenbeck