California Code, Penal Code - PEN § 30348

(a) Except as provided in subdivision (b), the sale of ammunition by a licensed vendor shall be conducted at the location specified in the license.

(b) A vendor may sell ammunition at a gun show or event if the gun show or event is not conducted from any motorized or towed vehicle.

(c) For purposes of this section, “gun show or event” means a function sponsored by any national, state, or local organization, devoted to the collection, competitive use, or other sporting use of firearms, or an organization or association that sponsors functions devoted to the collection, competitive use, or other sporting use of firearms in the community.

(d) Sales of ammunition at a gun show or event shall comply with all applicable laws including Sections 30347, 30350, 30352, and 30360.