DeFlock Lowell, which opposes the technology, filed the complaint after learning of the vote. The group argues that a decision to resume operating a citywide surveillance system should have been made in public, with residents able to hear the debate and weigh in.

"Ideally, we'd like to see what I believe 20 other communities in Massachusetts have done, and that would be to eliminate Flock and any other service providers from the city of Lowell," said Matthew Lucas of DeFlock Lowell.

Lowell had joined a growing list of Bay State municipalities to cut ties with Flock Safety in recent months. Dozens of communities across Massachusetts have ended or paused contracts with the company amid mounting public concern over automated license plate readers, which capture and store vehicle location data. The city council suspended the cameras in September over those privacy worries.

City Councilor Sean McDonough was the sole vote against reactivating the system. He questioned why the decision was made outside public view.

"I truly don't understand why my colleagues felt that was the right thing to do," McDonough said of the executive session vote.

City Councilor Rita Mercier defended the decision and the process. "The value of good outweighs the bad, so I support the Flock cameras, and we agreed to have them turned on, and people found out about it, and they're upset about it," she said.

Asked why the vote was taken behind closed doors, Mercier said: "It was on the agenda. That's why we went in there. The rest, you'll have to ask the city manager, and that is not me."

City Manager Thomas Golden Jr. and the Lowell Police Department did not respond to requests for comment.

The reactivation comes as Flock Safety faces intensifying scrutiny in Massachusetts. Communities including Quincy and New Bedford have wrestled with the cameras in recent months, and a court ruling has added to the legal uncertainty surrounding the technology. Critics argue that license plate readers amount to mass surveillance, logging the movements of residents who are not suspected of any crime and creating databases that can be accessed by law enforcement agencies far beyond the city that installed them.

Supporters, including Mercier, contend the cameras help police solve crimes and recover stolen vehicles. The debate in Lowell now centers not only on whether the cameras should operate, but on how the decision was made. The open meeting law complaint filed by DeFlock Lowell will likely be reviewed by the state attorney general's office, which enforces the statute. If the complaint is upheld, the vote could be challenged, and the city could be required to redo the decision in public.

For residents, the dispute raises questions about transparency at City Hall and about what safeguards, if any, govern the data collected by the cameras now that they are back online. DeFlock Lowell says it wants the city to follow the path of other Massachusetts communities and end its relationship with Flock entirely.