More than a dozen unions in the Washington region rallied on Wednesday against a Montgomery County law aimed at the collective bargaining rights of the local police union.

Passed unanimously by the County Council last year, the law curtails certain bargaining rights that the Fraternal Order of Police Lodge 35 has held for decades. The law permits the union to bargain on traditional rights, such as wages and vacation time, but not on other aspects of a police officer’s job, such as something as seemingly small as checking e-mail.

County officials said the additional rights hamstrung police officials. Union officials say the rights protect police officers from arbitrary and potentially harmful decisions by management. Using a petition with nearly 35,000 signatures, the union successfully put the law to a referendum. Now, county officials are urging residents on their Web site to uphold the law.

At a news conference in a Gaithersburg hotel Wednesday, leaders from several FOP branches across Maryland, as well as Montgomery’s government workers union, the District’s teachers union, the private service workers union UNITE HERE and others decried the County Council and County Executive Isiah Leggett (D) for supporting the law.

“An injury to the FOP is an injury to organized labor, and we will not tolerate it,” said Joslyn Williams, president of the Metropolitan Washington Council, AFL-CIO, whose remarks prompted to a standing ovation by union members.

In response, county spokesman Patrick Lacefield said that unions often support each other, adding, “I’m surprised there weren’t more.” He said that some police union members have reached out to county officials to support the law, but he declined to give names of these members and to set up interviews with them.

In recent weeks, the vast majority of Democratic and Republican precinct officials have indicated their support for the law. But several elected officials attended Wednesday’s press conference to express their dissent.

“My fear is that this is just the start,” said Del. Charles E. Barkley (D-Montgomery) at the press conference. “I think that this is the start, that this is going to lead to getting rid of some collective bargaining rights that [other unions] may have.”

County officials have said they are friendly to labor and respect collective bargaining rights. Lacefield added that that he’s not concerned by the opposition. “It’s a free country,” he said.