Cal. VEH § 27600

No person shall operate any motor vehicle having three or more wheels, any trailer, or semitrailer unless equipped with fenders, covers, or devices, including flaps or splash aprons, or unless the body of the vehicle or attachments thereto afford adequate protection to effectively minimize the spray or splash of water or mud to the rear of the vehicle and all such equipment or such body or attachments thereto shall be at least as wide as the tire tread. This section does not apply to those vehicles exempt from registration, trailers and semitrailers having an unladen weight of under 1,500 pounds, or any vehicles manufactured and first registered prior to January 1, 1971, having an unladen weight of under 1,500 pounds.