California Gov. Gavin Newsom has vetoed legislation that would have required dozens of his state’s largest cities, counties and educational districts to use independent commissions to draw voting districts, dealing a setback to “redistricting reform” advocates.

“We’re frustrated, confused and deeply disappointed,” Jonathan Mehta Stein, executive director of voting rights group California Common Cause, said Monday. He added: “We were hopeful that this was an opportunity for California to show the rest of the nation what it looks like to put gerrymandering behind us.”

California’s local redistricting methods came under scrutiny last year following a leaked recording of a private discussion among several Los Angeles City Council members. The officials — all Latino Democrats — used crude and racist comments while plotting to bolster their political power at the expense of Black voters.

Newsom vetoed a pair of bills Saturday that would have taken away redistricting power from elected officials in Los Angeles and dozens of other jurisdictions and instead given the responsibility to independent commissions of local residents.

In a statement, the Democratic governor said he supported the “goal of ensuring community control over the redistricting process” but was concerned a mandate to create independent commissions could end up costing the state tens of millions of dollars. It marked the second time in four years that he has vetoed legislation requiring independent redistricting commissions for some local governments.

Had Newsom signed the measure, California could have become the first state to mandate redistricting commissions for local jurisdictions over certain sizes, said Dan Vicuna, national director of redistricting and representation for Common Cause.

Boundaries for state and local legislative districts must be redrawn every 10 years to align with the latest U.S. census figures. Historically, that process has been carried out by elected officials who have a political interest in shaping districts to their advantage — a tactic known as gerrymandering.

But California voters shifted the responsibility for drawing U.S. House and state legislative districts to an independent panel of citizens following the 2010 census. Since then, voters in Colorado, Michigan, New York, Utah and Virginia have created redistricting commissions with varying levels of independence.

Some cities — including Austin, Texas and Santa Fe, New Mexico — also have adopted independent redistricting commissions. But such commissions remain relatively rare in local governments. In California, a 2016 state law allowed, but didn’t require, counties and cities to create redistricting commissions. More than a dozen have voluntarily done so, and separate state laws have specifically mandated redistricting commissions for Los Angeles County, San Diego County and a few other counties.

But the City of Los Angeles is among many local governments that remain in charge of drawing their own districts. A panel of academic experts recommended this year that independent commissions composed of city residents be used for future redistricting of the Los Angeles City Council and school board.

The legislation vetoed by Newsom would have applied more broadly. It sought to require independent redistricting commissions in all cities and counties with more than 300,000 residents and in community college or public school districts with more than 500,000 residents. Elected officials, political candidates, their larger financial donors and lobbyists would have been excluded from the commissions.

Despite the veto, the California legislation still could provide a model ahead of the next round of redistricting based on the 2030 census, said Justin Levitt, a professor at Loyola Marymount University Law School in Los Angeles who created the All About Redistricting website.

“Advocates will certainly press the issue in other states,” Levitt said, “and I’d be surprised if at least some other states didn’t seriously consider what California declined to do.”

Newsom did sign separate legislation Saturday that also is intended to discourage gerrymandering. It tightens redistricting criteria by prohibiting local entities from adopting districts for the purpose of favoring or discriminating against incumbents.