Citing an opinion from legal counsel, the chairman of the Martha’s Vineyard Commission last Thursday night blocked a move by one of his colleagues to revisit the roundabout decision, spurring a discussion about the role of the commission and whether the organization’s decisions are reversible.

Two weeks ago, commissioner Leonard Jason Jr. announced his intention to call for a vote to rescind the MVC’s October approval of the roundabout, pointing to recent nonbinding referendum votes in five Vineyard towns that showed overwhelming voter disapproval of the project planned for the blinker intersection in Oak Bluffs.

But when Mr. Jason made the motion Thursday night, commission chairman Chris Murphy put a stop to it.

“This is really a political issue. This is not a regulatory issue,” he said. “The forum for the petitions, and the political likes and dislikes, is the Oak Bluffs selectmen’s meetings.”

“We’re a regulatory body and we made a regulatory finding,” Mr. Murphy continued, adding that only an egregious action by the applicant could cause a rescission.

“In my role as chairman I have to rule that this motion is out of order and that that’s the end of it,” he said. “Are you comfortable with that?”

“Of course not,” Mr. Jason responded. “With all due respect.”

The commission voted 7-6 in October to approve the roundabout, and Mr. Jason, a vocal critic of the project, called for a vote to rescind less than a month later. The commission was deadlocked at 6-6, with Mr. Murphy casting the deciding vote, and the decision stood. Commissioner Brian Smith, who voted against the project, was not at the meeting.

On Thursday night Mr. Murphy said there was nothing in the commission’s bylaws to allow for a vote to be rescinded. He then passed around a letter from the commission’s legal counsel that advised against allowing the vote.

“The MVC must act within the confines of its enabling legislation. That legislation does not grant express authority to rescind a DRI approval,” wrote Gareth I. Orsmond.

Mr. Jason, joined by Mr. Smith, argued strenuously for having the vote to rescind, saying the commission had made a mistake.

Mr. Smith said the roundabout was not a properly approved project. ”If we really screw up and we really make a bad decision, then we can never go back and fix it?” he said. “We can never say we made a mistake?”

Mr. Jason moved forward with an appeal of Mr. Murphy’s decision, spurring further debate. “I feel that we as elected officials have an obligation to do what is right for the Vineyard,” he said. He noted that Mr. Orsmond cited misrepresentation as potential grounds for rescission, and said there were misrepresentations in the roundabout case: that the project had approval from the Land Bank, and the project would not affect the towns of Vineyard Haven and Edgartown.

“Somebody has to speak for the people on this Island,” he said, “and that’s us.”

But others argued the roundabout was a properly approved project and rescission may be illegal and hurt the commission’s reputation as a trustworthy body.

“Regardless of whether this is about the roundabout or an ice cream stand, it’s important that we do our job the right way,” commissioner Doug Sederholm said, “and the right way is to have predictability and finality in what we do. Once we make a decision it’s done, and people can rely on it.”

Some who were against the roundabout said they disagreed with rescission and supported Mr. Murphy’s decision.

“I voted against this project. I’m sorry it got approved,” said commissioner Linda Sibley. “I’m certainly not going to vote to rescind, because I think it’s illegal.”

Mr. Jason called for a vote to override the chairman’s decision not to have a vote, which was defeated 9-4.