Cal. Penal Code § 25615

Section 25400 does not apply to, or affect, the possession or transportation of unloaded pistols, revolvers, or other firearms capable of being concealed upon the person as merchandise by a person who is engaged in the business of manufacturing, importing, wholesaling, repairing, or dealing in firearms and who is licensed to engage in that business, or the authorized representative or authorized agent of that person, while engaged in the lawful course of the business.