In a blow to Mayor Eric Adams and powerful union leaders, a Manhattan judge temporarily blocked the city Friday from switching all public sector retirees to a privatized healthcare plan. 

Manhattan Supreme Court Justice Lyle Frank sided with retirees, issuing a temporary restraining order that prevents the city from proceeding with a plan to move the city’s 250,000 retirees to a Medicare Advantage plan managed by Aetna.

Frank wrote that the arguments by the legal teams representing retirees are likely to prevail on the merits of their case, pausing a transfer that was supposed to take effect Sept. 1. 

“The petitioners have shown that numerous promises were made by the City to then-New York City employees and future retirees that they would receive a Medicare supplemental plan when they retired, and that their first level of coverage once that retired would [be] Medicare,” Frank wrote.

A City Hall spokesperson did not immediately respond to THE CITY’s request for comment. 

“We are extremely disappointed by this misguided ruling,” mayoral spokesperson Jonah Allon told Gothamist. “The city’s Medicare Advantage plan, which was negotiated in close partnership with the Municipal Labor Committee, improves upon retirees’ current plans, including offering a lower deductible, a cap on out-of-pocket expenses, and new benefits, like transportation, fitness programs and wellness incentive.”

In a statement after the decision, the group representing municipal retirees cheered the court’s decision to “stop the City from violating retirees’ healthcare rights.”

“We call on the City and the Municipal Labor Committee to end their ruthless and unlawful campaign to deprive retired municipal workers of the healthcare benefits they earned,” said Marianne Pizzitola, the president of the New York City Organization of Public Service Retirees, one of the lead plaintiffs in the case.

It’s not the first time the courts have sided with retired city workers on the issue: Retirees successfully sued last year to block a previous version of the plan. In that case, a judge barred the city’s alternative offer, under which retirees would have been allowed to keep their existing Medicare with Medigap health plan — if they paid $191 a month.

The Aetna deal is key to locking in an estimated $600 million in annual savings agreed to by municipal unions to help pay for wage boosts and benefits. 

Many retirees fear that the long-planned switch from traditional Medicare to the privately run Medicare Advantage could increase their health care costs and make it more difficult to get approvals for procedures.

The Municipal Labor Committee, a consortium of 102 public sector unions, voted on March 9 to back the plan with Aetna. In a statement from March, Harry Nespoli, the organization’s chairperson, stood by the switch.

“With today’s City Hall announcement, our retired city employees will retain high-quality, premium-free healthcare in a unique Medicare Advantage plan designed to meet their needs,” Nespoli said.

A spokesperson for the Municipal Labor Committee did not immediately respond to a request for comment about the temporary restraining order.