A JUDGE HAS sided with Boston Police Commissioner William Evans and ruled that he has authority to assign officers to a body-worn camera pilot project over the objections of the Boston Police Patrolmen’s Association.

In a decision handed down Friday morning, Suffolk Superior Court Judge Douglas Wilkins said Evans had the management authority to order officers to wear cameras, even though an agreement reached in July between the city and union called for the use of officers who volunteered to take part in the six-month pilot.

Not a single officer on the 1,500-member force volunteered for the pilot study, which aims to enlist 100 participants.

Wilkins said state law grants police commissioners wide latitude to direct the operation of their departments. He wrote that this “significant non-delegable management authority,” which includes authority over things like uniforms and weapons, extends to newer policing tools such body cameras.

“I am pleased with the Court’s decision to allow the pilot program to move forward,” Evans said in a statement. “I remain committed to working with the BPPA and their members to ensure a smooth implementation of the program.”

The union filed suit seeking an injunction to block the pilot program, which is scheduled to begin on Monday, arguing that the city violated the July agreement by moving to assign officers to wear cameras.

“I’m disappointed in the court’s ruling, but I still believe asking for the injunction was the right thing to do,” Patrick Rose, the union president, said in a statement. “If we don’t fight to preserve our collective bargaining rights, we could lose those rights.”

He insisted that the union supports the body camera pilot, despite its effort to block Evans from unilaterally moving ahead with the initiative.

“Injunction or no injunction, the BPPA is still committed to working with the City and the Department to make sure the citizens of Boston get a body-worn camera pilot program that does what it is supposed to do, while respecting the rights of citizens and police officers alike,” Rose said.

He gave no indication about whether the union would appeal.

Calls for body cameras have soared in the wake of a rash of killings by police of unarmed black men, some of them captured on civilian cellphone video. Advocates argue that having officers wear body cameras will decrease the unwarranted use of force by police and will also protect officers from assaults by civilians.

The union pointed to a recent Rand Corporation study suggesting that body cameras led to no change in officer use of force, while they were linked to a 15 percent increase in assaults against police.

Wilkins, in his 19-page ruling, said the study cited was far from conclusive in demonstrating harm from cameras.

In August, CommonWealth wrote about the Rand study in this look at the evidence on the effects of body cameras. The study authors urged caution in drawing firm conclusions on the findings, and outlined several possible explanations, including a greater tendency to report assaults by officers wearing cameras.

Many departments have begun using body cameras, but they became the focus of drawn-out negotiations in Boston. Evans himself initially expressed wariness of equipping officers with cameras, but he now says he is convinced they will bring accountability and transparency that is good for both residents and police officers.

Wilkins held two days of hearings earlier this week, which featured testimony from Evans and Rose.

Rose maintained that the union was fully behind the pilot program and did nothing to discourage officers from volunteering once the agreement with the city was reached in July.

The city presented evidence suggesting that the union did little to encourage members to take part. An attorney for the city said a memo from the union to members instructing them not to volunteer for the pilot, which was circulated in June before the agreement was reached on the pilot study, was posted on a station house bulletin board after the memorandum of agreement with the city had been signed.

The July agreement stated that the union “expresses its support of the [body-worn camera] pilot program and will endeavor to ensure its successful implementation.”

Wilkins wrote that “it appears likely that, at a minimum, the BPPA has not conveyed a strong message of support for officers to volunteer for the [body camera] program.”

“Had the Union mobilized even a small part of its membership, the Pilot Program would have proceeded as a voluntary program, avoiding any of the negative impacts allegedly flowing from the Commissioner’s orders,” wrote Wilkins. Saying that the union’s alleged injury is, “in significant part, self-inflicted,” Wilkins wrote that “an injunction effectively rewarding the BPPA for its lackluster efforts to ensure the [memorandum of agreement’s] successful implementation would be unjust.”

Mayor Marty Walsh applauded the ruling.

“I am pleased that Boston’s body camera program will move forward,” Walsh said in a statement. “The Boston Police Department will continue to be a leader in innovative, community-based policing, and I look forward to seeing the results of the body camera pilot program.”

The ACLU of Massachusetts also hailed the decision.

“This is a great moment for police accountability, police transparency and, really, for civil rights in Boston,” Matthew Segal, legal director of the state ACLU chapter, told reporters outside the courthouse after the decision was announced.

Segun Idowu of the Boston Police Camera Action Team, a community group that has been advocating the use of body cameras, said his organization has been pushing for a camera program for more than two years. “We’re pleased with the judge’s decision,” he said after the ruling. “We’re cautiously optimistic. The program has not yet begun, so anything can happen before Monday.”