An appeals court reinstated a New York City law forbidding police officers from compressing a suspect’s diaphragm, the latest turn in a protracted legal struggle over the measure passed two years ago.

The law was part of a broader effort to limit the kinds of physical restraints police officers could use in detaining someone, including chokeholds. Police unions sued almost as soon as the statute was passed, saying it was overly broad and would deter officers from physically restraining suspects, even if it was necessary or done in good faith.

A state Supreme Court judge in Manhattan agreed and struck down the policy last fall, saying its language was “unconstitutionally vague.”

In Thursday’s ruling, the Appellate Division ruled the judge had erred in striking down the policy and said the statute clearly explained what officers could and couldn’t do.

“A trained police officer will be able to tell when the pressure he is exerting on a person’s chest or back, in the vicinity of the diaphragm, is making it hard for the person to breathe, just as a driver should be able to tell when the amount of alcohol he consumed is making it unsafe for him or her to drive,” the panel wrote.

The use of chokeholds by police officers is already a felony under New York State law, and New York City Police Department guidelines forbid their use. The conduct forbidden by the law passed by the City Council includes chokeholds but also a litany of other physical restraints, including applying any pressure to someone’s neck or kneeling on a person’s back. Under the city law, either could be prosecuted as a misdemeanor.

The Council passed the law in the summer of 2020, as sweeping, nationwide protests against police brutality spilled into the streets after the death of George Floyd at the hands of Minneapolis police officers.

Even law enforcement officials who applauded banning chokeholds said at the time that they feared the law’s provisions were too broad and could put officers at risk of unfounded prosecution.

But the panel challenged assertions that the law lacked specificity. To pretend that police officers could not understand the difference between acceptable restraint and dangerous levels of compression was to make a poor argument, the judges said.

Patrick J. Lynch, the president of the city’s largest police union — which joined the lawsuit challenging the statute — chastised the judges for reinstating the law and said the ruling would deter officers from doing their jobs even as the city wrestles with an increase in some crimes.

“Our city leaders need to realize that this ruling deals a direct blow to our fight against the violence that is tearing our city apart,” said Mr. Lynch in a statement. “This ill-conceived law makes it virtually impossible for police officers to safely and legally take violent criminals into custody — the very job that New Yorkers are urgently asking us to do.”

The union did not immediately say whether it would appeal to New York’s highest court.