Cal. Penal Code § 26375

Section 26350 does not apply to, or affect, the open carrying of an unloaded handgun by an authorized participant in, or an authorized employee or agent of a supplier of firearms for, a motion picture, television or video production, or entertainment event, when the participant lawfully uses the handgun as part of that production or event, as part of rehearsing or practicing for participation in that production or event, or while the participant or authorized employee or agent is at that production or event, or rehearsal or practice for that production or event.