California Code, Business and Professions Code - BPC § 7574.22

A person registered as a proprietary private security officer shall carry on their person, while on duty, a valid and current proprietary private security officer's registration card or a hard copy printout of the bureau's approval from the bureau's internet website and either a valid driver's license issued pursuant to Section 12811 of the Vehicle Code or a valid identification card issued pursuant to Section 13000 of the Vehicle Code.  The registration shall be shown to any peace officer or bureau representative upon demand.