Business and Professions Code § 5359

(a) The issuance of a permit for the placing of an advertising display includes the right to change the advertising copy without obtaining a new permit and without the payment of any additional permit fee.

(b) The issuance of a permit does not affect the obligation of the owner of the advertising display to comply with a zoning ordinance applicable to the advertising display under the provisions of this chapter nor does the permit prevent the enforcement of the applicable ordinance by the county.