It’s been nearly three months since the U.S. Department of the Interior recognized an amended gaming agreement between the Mohegan Tribe and the state, action then hailed as a sure sign that an East Windsor casino project would soon move forward.

All that was necessary was for Interior to take the same action in regards to the Mashantucket Pequot Tribe’s amended agreement with the state.

The tribes, partners in the East Windsor project, are still waiting, presumably stewing last week as their nemesis, MGM Resorts International, opened a nearly $1 billion resort casino in Springfield, Mass., just 13 miles north of East Windsor. There, the site of the tribes’ proposed casino lies fallow.

Meanwhile, the state and the Mashantuckets have continued to press a federal lawsuit against Interior and its secretary, Ryan Zinke, who’ve argued that the government needn’t “deem approved” the Mashantuckets’ amended agreement because of the way in which the tribe’s original agreement with the state was reached. While Mohegan Sun, the Mohegans’ casino, operates under a “compact” negotiated by the tribe and the state, Foxwoods Resort Casino, owned by the Mashantuckets, operates under an agreement “prescribed” by the Interior secretary.

As outlined in a court document, when the Mashantuckets sought to negotiate a compact with the state in 1989, they had to sue to force the state to comply. When court-ordered negotiations failed to produce an agreement, the sides submitted their final proposals to a mediator. The sides ultimately agreed to abide by the proposal the mediator selected, and the Interior secretary published notice of the approval in the Federal Record.

In the current suit, filed in District Court in Washington, D.C., the Interior Department argues that the Indian Gaming Regulatory Act does not require it to act on proposed amendments to prescribed agreements.

That position, the state and the tribes have argued, is inconsistent with the stance Interior has held for more than three decades, “and it would severely undermine the purpose and congressional intent of IGRA.”

In a filing earlier this month, the state and the Mashantuckets call attention to a California case in which they say Interior successfully argued that tribal-state agreements prescribed by Interior and negotiated compacts should be treated the same — the opposite argument the department’s making in the Connecticut case.

Citing the doctrine of “judicial estoppel,” the Mashantuckets ask that the court prevent the defendants from “asserting a position that they so recently and resoundingly opposed.”

In the California case, an anti-casino group sought to prevent the North Fork Rancheria of Mono Indians from opening a casino, noting that the tribe’s gaming agreement with the state had been prescribed by the Interior secretary — much like the Mashantuckets’ — rather than reached through negotiations leading to a compact.

“Secretarial procedures, as the Defendants (Interior) argued … are ‘intended to provide a full substitute for a compact, and nothing in IGRA’s language provides for a ‘second class’ compact,” lawyers for the state and the Mashantuckets write. “That is precisely (the Mashantucket Pequots’) argument … yet now, because it is advantageous to their litigation position of the moment, the Defendants ask this Court to treat the Pequot Compact as a second class compact.”

Interior takes issue with the state and the Mashantuckets’ argument, claiming in a document filed Friday that IGRA’s requirement that the Interior secretary approve or disapprove an amended agreement within 45 days of its submission — with failure to do one or the other considered approval — applies only to negotiated compacts, not prescribed agreements.

Interior’s handling of the Connecticut tribes’ amended gaming agreements prompted members of the state’s congressional delegation to ask for an investigation.

Democratic Sens. Richard Blumenthal and Chris Murphy and Reps. Joe Courtney, D-2nd District, and John Larson, D-1st District, first called for the probe in February, citing Interior’s “highly unusual decision” to take no action regarding the amendments. In a letter to the top official in Interior’s Office of Inspector General, the lawmakers cited reporting that “raises serious concern about the role of money and lobbyists” in the decision-making.

When Interior announced May 31 that it would publish notice of the Mohegans’ amended agreement the following day in the Federal Register, Blumenthal said the investigation should continue. Two weeks later, the others who had asked for the investigation joined the senator in renewing their request.

A message left for a spokesman for the Interior Department’s inspector general’s office went unanswered Monday.

b.hallenbeck@theday.com