State’s authority over Mashpee Wampanoag could determine next chapter in land trust saga.

As members of the Mashpee Wampanoag Tribe celebrate their culture this weekend at the 96th annual powwow with food, dancing and music, the shifting clouds of uncertainty continue to hover over one of their greatest shared assets: land.

The U.S. Department of the Interior on Friday declined a request by the tribe to suspend a review of whether it qualifies for land into trust under an alternative category to the one a federal judge rejected last year.

But the move could be good news for the tribe’s hopes to build a casino in Taunton, seemingly dealt a setback earlier in the week when it asked Interior officials to hit the pause button on the review that had, until the latest development, been destined to end badly for the tribe.

Instead of suspending its review or moving forward with a decision on the issue prepared on June 19, the agency instead plans to further analyze an aspect of the case that had not been previously explored: whether the state’s authority over the tribe could be considered in place of the federal government’s authority in determining whether it met one of the alternative definitions of Indian required for land to be taken into trust on its behalf.

Both sides in the lawsuit brought by neighbors of the land where the proposed casino would be built had referenced a case decided in 1975 by the U.S. Court of Appeals for the First Circuit, which found that in considering whether to admit Maine — which had previously been part of Massachusetts — as a separate state, Congress “had notice of Massachusetts’ exercise of authority over Indian affairs in the State,” Interior Associate Deputy Secretary James Cason wrote in a two-page letter sent Friday to Mashpee Wampanoag Tribe Chairman Cedric Cromwell.

That case raised a potentially important issue in the analysis of the remand of the case to the Interior by U.S. District Court Judge William Young that neither the tribe or the neighbors had explored, Cason wrote.

“To ensure a thorough analysis of this complex issue, I therefore request supplemental briefing from the parties on the question of whether the exercise of authority over the tribe by the Commonwealth of Massachusetts could be considered a surrogate for federal jurisdiction for purposes of the (Indian Reorganization Act’s) first definition of ‘Indian,’” Cason wrote in the letter, which was accompanied by the 33-page June 19 draft decision.

Under the June 19 decision, if it had been finalized, the tribe would not have qualified for land into trust because Cason had determined the tribe did not meet the first definition’s requirement that it had to have been under federal jurisdiction prior to 1934, leaving it to appeal the judge’s ruling on the second definition of Indian.

“The Mashpee Wampanoag Tribe is grateful that the U.S. Department of Interior today has provided a pathway forward in securing our reservation lands,” Cromwell said in a statement sent out with the Interior’s letter. “This evening I received a letter announcing the Interior Department decision to extend and expand the review process by inviting us to submit further materials demonstrating how our tribal history supports our rights to trust land.”

But a lawyer representing the Taunton neighbors called the issue raised by the Interior Department “a complete non-starter.”

“It’s not anything that makes sense in history or law,” attorney David Tennant said Saturday.

The tribe’s plan to build the First Light Resort and Casino on the Taunton land has faced fierce opposition from neighbors of the property who sued the federal government in February 2016, arguing that it had erroneously concluded it had the authority to take the land into trust for the Mashpee tribe under the second definition of Indian.

In August 2016, Young found in favor of the neighbors but said the government could also make a determination of whether the tribe qualifies for the land under the first definition, namely that it was under federal jurisdiction before 1934.

The tribe and the Interior Department chose to pursue that route as government lawyers exited the court case and the tribe asked for a pause in the proceedings while the determination was being made.