Legal Question in Business Law in California

I do not know of any such law nor do I think there is an Alcoholic Beverage Control Board regulation to this effect. Many places do not have security personnel, and if there were a universal requirement, we would have an unlikely number of violators. There is undoubtedly some authority for the ABCB to order, directly or indirectly, security or additional security at establishments with a record of problems, and municipalities have some control through their public-nuisance abatement policies and procedures,

The most common source of a requirement of security personnel is the use permit issued by the local authorities. For night clubs and bars those permits are usually very detialled conditional use permits and include revocation and modification provisions that allow the local entity to change the conditions of use, which they quickly do when a venue becomes a problem, requiring security personnel usually being one of the first things added. Of course many club opperators add security before they get in trouble with the city/county, because it's just good business, or because it's required by their insurance company.