CA Civ Code Section 3069

Any lien provided for in this chapter for labor or materials, or for storage or safekeeping of a vehicle when abandoned on private property may be assigned by written instrument accompanied by delivery of possession of the vehicle, subject to the lien, and the assignee may exercise the rights of a lienholder as provided in this chapter. Any lienholder assigning a lien as authorized herein shall at the time of assigning the lien give written notice either by personal delivery or by registered or certified mail, to the registered and legal owner of the assignment, including the name and address of the person to whom the lien is assigned.