Bail is a method to ensure people return to court that requires defendants to post cash or a bond, which they forfeit if they fail to show up for proceedings. Since the 1970s, New York judges have been able to consider only the risk of flight in setting bail, not public safety. The amount can range from a few hundred dollars to millions.

Opponents of cash bail have long argued that it criminalizes poverty, tilting the justice system in favor of wealthy defendants. In New York, the inequities of the system were crystallized when a Bronx teenager named Kalief Browder spent three years on Rikers Island because his family could not raise $3,000, only to have charges dropped in 2013 for lack of evidence. He later took his own life.

After his death, the movement to abolish cash bail grew stronger, and last year the governor and the Democratic-led State Legislature passed the new law, which bans imposing bail for most misdemeanors and nonviolent felonies.

The rules require judges to impose the “least restrictive conditions” that will assure people return to court. Those include supervised release, travel restrictions and, for some serious offenses, electronic monitoring.

In recent weeks, courts around the state have begun releasing batches of defendants from jails under the new rules to avoid a rush as the new year starts, and the law’s opponents have pounced on recent cases in which people out on bail committed crimes as harbingers of the future.

Supporters of the bail law say critics are being alarmist: Judges will still be able to set bail for almost all violent felonies, they point out, and the old law unfairly discriminated against the poor. Neither Gov. Andrew M. Cuomo nor Democratic legislative leaders have given any sign that they might delay or significantly alter the law, despite the intensifying opposition.

“I know change is scary, change is hard,” said Senator Andrea Stewart-Cousins, the Westchester County Democrat who leads Albany’s upper chamber. “But, again, we are talking about justice.”