Mayor Eric Adams on Friday vetoed a bill banning most forms of solitary confinement in city jails.

The bill was approved by the City Council in December. It does allow the Department of Correction to isolate detainees for up to four hours at a time during a 24-hour period if they have been deemed a threat to themselves or others. It also puts strict guidelines on how the correction department can run its most restrictive housing units reserved for its most dangerous detainees.

Jail reform advocates have said the psychological toll solitary confinement takes on inmates can be severely damaging.

Adams and the city correction officers union have consistently raised objections to the legislation.

In a statement issued Friday, Adams said if the bill had taken effect, “the Department of Correction would no longer be able to protect people in custody, or the union workers charged with their safety, from violent individuals.”

A press release issued by the city also mentioned that the federal monitor expressed concerns with many of the bill’s provisions last week. A letter from the monitor read, "The Monitoring Team has deep concerns about many of the bill’s provisions related to the use of restrictive housing, de-escalation, emergency lock-ins, and the use of restraints and escort procedures. Many of the provisions, as currently drafted, could inadvertently undermine the overall goals of protecting individuals from harm.”

“I implore the City Council to work with our administration and follow the federal monitor’s guidance to abandon this misguided bill,” Adams said.

In a joint statement in response to the veto, City Council Speaker Adrienne Adams and City Council criminal justice chair Sandy Nurse said solitary confinement “by any name, has been proven to cause physical, psychological, and emotional harm, and its use has contributed to continued violence and deaths on Rikers Island.”

“The Council stands by its passage of this legislation and will take the steps to enact this law over the Mayor’s veto,” the statement said.

They also said in their statement that the public process on the bill “offered considerable opportunities for feedback, and we specifically sought the federal monitor's feedback in advance, but our outreach was completely ignored.”

City Hall has said it does not use solitary confinement on Rikers Island, and in a letter to the city clerk about the veto, Adams wrote that solitary confinement “was already eliminated from New York City jails in 2019.” But some advocates have disputed this, arguing that there are restrictive housing units that amount to severe isolation.

Adams previously vetoed a separate bill related to public safety Friday morning. That bill would require lower-level interactions between the police and civilians to be recorded.

Both pieces of legislation passed the City Council with a "veto-proof" majority, meaning they passed with enough support that the council could override a mayoral veto. Adams will have to peel away a handful of supporters of the bill and bring them to his side to prevent an override.