Mayor Eric Adams declared a state of emergency in New York City jails on Saturday and issued an executive order that blocked key parts of a local law that would have banned solitary confinement in the jails.

The order, one of three Mr. Adams issued on Saturday that pertained to the jails, was an unusual step that came only one day before the law was set to go into effect. It was the latest move in a protracted battle over the legislation between the City Council and the mayor, a former police captain who ran for office on a public safety message. After Mr. Adams vetoed the bill in January, arguing that it would make jail staff and detainees less safe, the Council issued a rare override of his veto.

The law would have banned solitary confinement for detainees who were accused of breaking jail rules, beyond a four-hour “de-escalation period” during an emergency. It would also have banned the use of handcuffs or shackles to restrain detainees riding in Correction Department vehicles.

“The Department of Correction has been laser focused on reducing violence in our jails to protect both the people in our care and correctional staff who boldly serve our city,” Amaris Cockfield, a City Hall spokeswoman, said in a statement, noting that the federal monitor who oversees the jails had raised concerns about the law.

The state of emergency is expected to remain in effect for 30 days, though Mr. Adams can extend it for additional 30-day periods.

It was unclear on Sunday what steps the Council would take in response. Emergency executive orders can only be challenged through the court system. But the mayor’s actions were attacked by elected officials who had backed the bill, including Jumaane Williams, the city’s public advocate, who called the decision an “abuse of power” and “inexcusable.”