MASHPEE — Federal Indian law experts and tribes across the country are keeping a close eye on the Mashpee Wampanoag Tribe, which is just days away from learning whether the U.S. Department of the Interior — the agency charged with protecting tribal trust assets — can secure its land.

Interior officials have said there will be a decision by Sept. 21 on whether the federal agency will be able to keep the tribe’s 321 acres of land in Mashpee and Taunton in trust, according to the tribe and an attorney for opponents of the tribe’s planned $1 billion casino.

Whatever the agency decides will have implications for tribal nations elsewhere.

“This decision is going to be telling about the current administration’s land policies toward Indians,” said Derrick Beetso, general counsel for the National Congress of American Indians.

The Interior Department was sued back in 2016 after taking the Cape-based tribe’s land into trust, and a federal judge ruled that the Secretary of the Interior did not have the authority to do so because the tribe was not under federal jurisdiction at the time of the passage of the Indian Reorganization Act in 1934. That statute remains the primary governing tool over Indian affairs, promoting Indian self-determination and self-government.

The suit, as in similar cases, rested on the interpretation of four words: “now under federal jurisdiction,” a phrase that has vexed tribes seeking trust status for newly acquired land with the federal government over the years, most notably the Narragansett Tribe's efforts in Rhode Island which culminated in the Supreme Court decision known as Carcieri v. Salazar.

But the Carcieri decision never established the criteria by which a tribe could demonstrate it was under federal jurisdiction, prompting the Interior’s solicitor to issue an interpretation of the ambiguous phrase in 2014.

In her written interpretation, Hilary Tompkins rejected the idea that there is one “clear and unambiguous meaning” of “under federal jurisdiction,” writing that the only information available to help decipher what Congress meant by the phrase was gleaned from a Senate hearing on May 17, 1934 — that it was intended as “a means of attaching some degree of qualification to the term ‘recognized Indian tribe.’” She concluded that the Interior Department will continue to take land into trust on the basis of a two-part inquiry that would “fill in gaps where Congress has been silent.”

Tompkins’ interpretation makes it “clear that there are a number of ways that a tribe can be under federal jurisdiction,” Beetso said.

And the Interior Department is presently examining one possible way in connection with the Mashpee tribe's status. After issuing a draft decision on June 17, 2017, which concluded the tribe was not under federal jurisdiction in 1934, the agency is now considering whether the relationship between the tribe and Massachusetts could act as a substitute for the federal jurisdiction requirement.

Beetso said there is a lot riding on the impending decision, including some measure of precedent for how these “under federal jurisdiction” questions will be settled.

“Indian Country will be watching,” he said.

Should the Interior rule against the tribe’s wishes, it could mean a number of things, but mostly more legal confusion, according to some experts.

“The most straightforward thing that could happen is the land would be transferred into fee simple status,” said Gregory Ablavsky, professor of law at Stanford University Law School. “Ownership would not change. It’s not as if the Mashpee Wampanoag would stop owning the land.”

But it would cease to be Indian Country for jurisdictional purposes, Ablavsky said, opening up the land to being taxed and regulated at the local and state levels.

“This would mean the tribe wouldn’t be able to exercise civil jurisdiction over their land, which includes the right to regulate, the ability to impose zoning ordinances, environmental regulations, but then also civil jurisdiction in the courts as well,” Ablavsky said. “Tribal courts can hear disputes, and in certain instances, they can hear disputes against non-tribe members. Taking that away might limit their ability to do that.”

Before the Interior’s 2015 decision to take the land into trust, the tribe’s land was owned by the Tribal Council as a registered 501(c)(3) organization, and, while tax exempt, it was subject to state and local regulations.

Mashpee Wampanoag Tribal Chairman Cedric Cromwell has repeatedly said a negative determination from the Interior Department would mean the disestablishment of the tribe’s reservation. But only Congress has the authority to terminate a reservation if the land had been “finally established,” according to Bethany Berger, an Indian law scholar at the University of Connecticut School of Law.

The Interior issued a reservation proclamation of the tribe’s land in January 2016, and based on the procedural history in the 2015 decision, Berger said the land appears to be securely in trust, despite the court ruling.

“All the federal government has to do is give it back to the tribe,” she said, noting that the trust status would be removed.

But that transfer would have to be green-lighted through federal legislation, Ablavsky said. There are two bills before the House of Representatives and the Senate that seek to reaffirm the reservation and bar future legal challenges to it in court.

It’s still unclear if the removal of trust status would mean the end of the tribe’s reservation. The land would revert to the tribe in fee simple, but it would still be “within the bounds of the reservation,” Ablavsky said. “All of this is unsettled because there’s not much precedent here.”

Either way, a negative finding would be a step in the wrong direction with respect to the federal government’s relations with tribes, said Robert Anderson, director of the Native American Law Center at the University of Washington School of Law.

“It would be totally inconsistent with federal Indian policy since the 1950s,” Anderson said.

U.S. Rep. William Keating, D-Mass., who introduced the pending legislation to end the tribe’s legal trouble, previously said if the Interior Department didn’t find another route to keeping the land in trust, the tribe would lose access to a variety of funding sources, including for social services, housing, education and environmental programs.

Additionally, losing trust status would cast doubt over the tribe’s casino efforts, particularly if the tribe's lands were to be subsumed under state and local jurisdiction and subject to taxation.

If the Interior Department cannot find an avenue to maintaining the trust agreement, it could mean the end of the tribe's casino bid as it stands, said John “Jim” Peters Jr., executive director of the state Commission on Indian Affairs and a Mashpee Wampanoag Tribe member.

“I don’t see it going anywhere at that juncture,” Peters said. “I suppose they could try to do a commercial casino, or bid for it in the region. But it would have to compete with other proposals.”

Under the Indian Gaming Regulatory Act, the tribe could still pursue a casino so long as it has a reservation. It just may be more costly, Peters said.

It's still unclear where the Interior Department stands on the tribe's land in trust. While testifying before a congressional hearing on Keating’s bill on July 24, Darryl LaCounte, acting director of the Bureau of Indian Affairs, said his department was not prepared to take a position on the legislation.

“Not to my knowledge,” LaCounte said about whether the agency would rule against the tribe. “It is in trust right now.”

— Follow Tanner Stening on Twitter: @tsteningCCT.