Members of the Wampanoag Tribe of Gay Head (Aquinnah) who oppose a casino have successfully petitioned for another vote on the issue at the tribe’s general membership meeting next month, officials confirmed last night.

Voting takes place on August 16. The ballot measure aimed at halting the project comes as tribal leaders have announced the project to convert the tribe’s community center into a class II gambling hall is moving ahead, with plans to open the facility this year.

That triggered a cease-and-desist letter last week from the town of Aquinnah; the tribe in turn has said the town’s letter has no authority over the casino project.

A petition drive challenging the conversion of the tribal community center to a casino drew more than 70 signatures, well more than the 50 necessary to force a vote of tribe members, said Beverly Wright, a former tribal chairwoman and opponent of the project.

“Our petition states that we want to repeal all resolutions, votes, et cetera, that have to do with turning the community center into a casino,” Ms. Wright said Sunday. “We want all those votes repealed.”

The upcoming vote at the tribe’s quarterly membership meeting on the third Sunday in August was confirmed by tribal chairman Tobias Vanderhoop, who earlier this month had announced plans to push forward with the casino project.

Opponents of the casino will need a two-thirds majority to overturn earlier votes to authorize it, said Mr. Vanderhoop. He has pledged to carry out the will of the tribal membership on the casino effort, and said the latest vote will be no different.

“As I’ve mentioned all along, the will of the people is the will of the people. So the outcome of the vote will have a huge [impact],” Mr. Vanderhoop said. “The vote of the people will be heard and will be carried out.”

While he was initially reluctant to discuss his own vote, the tribal chairman added that he believes as a practical matter, “it would show a deep level of instability not to go forward” with the project, especially since the tribe has already entered into legal agreements over the conversion project.

Ms. Wright said she and other tribe members who oppose the casino will call members in the coming weeks to explain their point of view. “We’re going to burn the candle at both ends,” she said. The last general membership vote to challenge the casino project was in February 2014, and it failed by two votes, she said.

The exact wording of the ballot question was unavailable last night, but Mr. Vanderhoop indicated that it would include the tribal council’s decision to transfer the Community Center over to tribe’s gaming arm, the Aquinnah Wampanoag Gaming Corp., a necessary step in converting the building to a casino.

Four days before the general membership vote, on August 12, U.S. District Court Judge F. Dennis Saylor IV will hear legal arguments on whether the tribe has the right to build and operate a class II gaming facility in Aquinnah.

Lawyers for the tribe and its gaming corporation say the 1988 Indian Gaming Regulatory Act supersedes any state or local prohibitions on gambling in Aquinnah, while the town, the state and the Aquinnah Gay Head Community Association say an earlier settlement with the tribe, codified in state and federal legislation, prohibit gaming on tribal lands in Aquinnah.