Going after public sector unions at all is extremely difficult. The most successful attempt to do so that I'm aware of was Gov. Scott Walker's in Wisconsin. And even he didn't go after the law enforcement unions. (It might be possible to split off the police unions from the prison guard unions, but it's not clear to me that it is.)
Law enforcement unions are one of the few American institutions with completely bipartisan protection. Democrats don't go after them because Democrats are pro-union. Republicans don't go after them because Republicans are pro-police. Furthermore, you really don't want to pick a fight with police unions. What happens if police officers and prison guards go on strike? It's against the law in many places, but if the police are on strike, who's going to enforce that? There is a very significant risk that you'd have to call up the National Guard just to maintain public order. And even then, how many National Guardsmen does California have? How many LEOs? And most of those National Guardsmen are not actually trained in law enforcement. In effect you would be declaring martial law. It's not worth it.
Law enforcement unions are one of the few American institutions with completely bipartisan protection. Democrats don't go after them because Democrats are pro-union. Republicans don't go after them because Republicans are pro-police. Furthermore, you really don't want to pick a fight with police unions. What happens if police officers and prison guards go on strike? It's against the law in many places, but if the police are on strike, who's going to enforce that? There is a very significant risk that you'd have to call up the National Guard just to maintain public order. And even then, how many National Guardsmen does California have? How many LEOs? And most of those National Guardsmen are not actually trained in law enforcement. In effect you would be declaring martial law. It's not worth it.