Cal. Sts. & Hy. Code § 731
Any vehicle or structure parked or placed wholly or partly within any state highway, for the purpose of selling the same or of selling therefrom or therein any article, service or thing, is a public nuisance and the department may immediately remove that vehicle or structure from within any highway.
Any person parking any vehicle or placing any structure wholly or partly within any highway for the purpose of selling that vehicle or structure, or of selling therefrom or therein any article or thing, and any person selling, displaying for sale, or offering for sale any article or thing either in or from that vehicle or structure so parked or placed, and any person storing, servicing, repairing or otherwise working upon any vehicle, other than upon a vehicle which is temporarily disabled, is guilty of a misdemeanor.
The California Highway Patrol and all peace officers from local law enforcement agencies may enforce the provisions of this chapter with respect to highways under their respective jurisdiction and shall cooperate with the department to that end. Whenever any member of the California Highway Patrol or any peace officer from a local law enforcement agency removes a vehicle from a highway under the provisions of this section, then all of the provisions of Article 3 (commencing with Section 22850), Chapter 10, Division 11 of the Vehicle Code with reference to the removal of a vehicle from a highway shall be applicable.
This section does not prohibit a seller from taking orders or delivering any commodity from a vehicle on that part of any state highway immediately adjacent to the premises of the purchaser; prohibit an owner or operator of a vehicle, or a mechanic, from servicing, repairing or otherwise working upon any vehicle which is temporarily disabled in a manner and to an extent that it is impossible to avoid stopping that vehicle within the highway; or prohibit coin-operated public telephones and related telephone structures in park and ride lots, vista points, and truck inspection facilities within state highway rights-of-way for use by the general public.
Ca. Sts. and High. Code § 731