Cal. Penal Code § 27340
(b) All firearms carried onto the premises of a gun show or event by members of the public shall be checked, cleared of any ammunition, secured in a manner that prevents them from being operated, and an identification tag or sticker shall be attached to the firearm, prior to the person being allowed admittance to the show. The identification tag or sticker shall state that all firearms transfers between private parties at the show or event shall be conducted through a licensed dealer in accordance with applicable state and federal laws. The person possessing the firearm shall complete the following information on the tag before it is attached to the firearm:
(c) Any ammunition carried onto the premises of a gun show or event by members of the public shall be checked and secured in a manner that prevents the ammunition from being discharged. An identification tag or sticker shall be attached to the ammunition prior to the person being allowed admittance to the show. The identification tag or sticker shall state that all ammunition transfers between private parties at the show or event shall be conducted through a licensed dealer or ammunition vendor in accordance with applicable state and federal laws. The person possessing the ammunition shall complete the following information on the tag before it is attached to the ammunition: