California Insurance Code - Sections 758.5

758.5. (a) No Insurer shall require that an automobile be repaired at a specific automotive repair dealer, as defined in Section 9880.1 of the Business and Professions Code.
            (b) (1) No insurer shall suggest or recommend that an automobile be repaired at a specific automotive repair dealer unless either of the following applies:
                                    (A) A referral is expressly requested by the claimant.
                                    (B) The claimant has been informed in writing of the right to select the automotive repair dealer.