More than 100 people signed on for an internet videoconference with the chairman and vice chairwoman of the Mashpee Wampanoag tribe, Cedric Cromwell and Jessie Little Doe Baird, Monday afternoon.

The listening session was organized by the First Congregational Church of West Tisbury to learn about the recent federal decision to revoke reservation status for the 321 acres of land the government holds in trust for the Mashpee.

Taking the land would end the tribe’s right to govern itself, both leaders said.

“Sovereignty cannot exist without trust land,” Ms. Baird told the internet audience. “The trust lands are the boundary within which sovereignty is exercised.”

“They would disestablish our tribe, against American policy, against Native American law . . . and basically destroy us,” Mr. Cromwell said.

The tribe is fighting the decision by Secretary of the Interior David Bernhardt in the courts and also appealing to the public for support.

“This issue that we’re facing really is an existential crisis for us,” Ms. Baird said. “The United States of America recognizes that the tribes, indigenous people of this land, have paid for our right to continue to govern ourselves. We’ve paid with our blood and we’ve paid with our lands.”

There is no precedent or procedure for the federal government to take tribal lands out of trust, the tribal leaders said.

“I think that the administration, in a large sense, has anti-Indian policies across the board and I think one of the attempts of the administration is to diminish trust lands so that people outside of tribes can access tribes’ resources,” Ms. Baird said.

President Donald Trump’s casino interests are another likely reason for the federal decision announced in March, the Mashpee leaders said.

“It’s clear there’s a big force associated with the Trump administration (and) it’s related to gaming,” Mr. Cromwell said.

Responding to a text from an audience member, Ms. Baird said it was about whether the tribe might be more successful in the land fight if it agreed not to enter the gaming business on its reservation. It’s a query she’s heard before, she said, with a trace of weariness.

“Asking that question is like saying, do you think you would have an easier time with the Equal Rights Amendment if you would just stop asking for the equal pay part of it,” she said.

“If people have a right, they have a right.”

The current crisis is not limited to Native American tribal members alone, Mr. Cromwell said.

“If they’re denouncing the tribe, they’re denouncing equal opportunity and your rights as a citizen,” he said.

Mr. Cromwell also reminded listeners that the Mashpee Wampanoag provided food and other assistance to the Mayflower settlers and took part in the first Thanksgiving in 1621.

“This is the thanks my tribe gets,” he said. “We’re being attacked by our own country. Who would ever think this would happen?”