The union for sheriff's deputies filed a lawsuit after the Office of Inspector General ordered 35 deputies suspected of being "Banditos" or "Executioners" to answer questions about deputy gangs and show their tattoos.
The judge in his ruling found that the county is required to bargain with the union before making significant changes to their employment, such as being forced to show their tattoos.
RELATED: Deputy gangs still operating within LASD, report says
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The ruling is a preliminary injunction, meaning the investigation may only be blocked until the labor issue is resolved.
"I'm disappointed that deputy gangs will remain for now and I expect the county will appeal," Inspector General Max Huntsman said. "It's been a year and a half since California outlawed the gangs without meaningful investigation by law enforcement."
The Sheriff's Department has been plagued by allegations that ganglike groups of deputies ran amok within the agency.
The groups are accused of a variety of misconduct dating back decades, from controlling sheriff's stations and the jails, to harassing other deputies and the communities they police, to harming or fatally shooting civilians as part of gang rituals.
The Associated Press contributed to this report.