The bill will replace bail with a risk-assessment system, although it's still unclear how the system will work. It will take effect in October 2019.
Brown's signature gives the state's Judicial Council broad authority to reshape pretrial detention policies.
Each county will use the council's framework as a basis to set its own procedures for deciding whom to release before trial, potentially creating a patchwork system based on where a suspect lives.
Most suspects arrested for nonviolent misdemeanors will be released within 12 hours of being booked under the new law. Those facing serious, violent felonies will not be eligible for pretrial release.
The legislation gives officials 24 hours to determine whether other suspects should be released before trial. That time can be extended by 12 hours if necessary.
Some criminal justice reform advocates worry defendants will spend weeks in jail while their lawyers try to prove they deserve to be set free.
Opponents of the legislation say it gives judges too much power. Some worry dangerous people will go free and won't return for trial.
Supporters, including the Judicial Council headed by the state Supreme Court's chief justice, say the change will end the unfair practice of imprisoning people simply because they are poor. Incarceration should instead depend on the risk a defendant poses if they are released, they argue.
Other states such as New Jersey and New Mexico have overhauled their bail systems, although neither state has completely eliminated bail.
The Judicial Council is the policy-making body for California's courts. It creates rules and procedures to ensure consistency across the state.