California Code, Labor Code - LAB § 4062

(a) If either the employee or employer objects to a medical determination made by the treating physician concerning any medical issues not covered by Section 4060 or 4061 and not subject to Section 4610, the objecting party shall notify the other party in writing of the objection within 20 days of receipt of the report if the employee is represented by an attorney or within 30 days of receipt of the report if the employee is not represented by an attorney.These time limits may be extended for good cause or by mutual agreement. If the employee is represented by an attorney, a medical evaluation to determine the disputed medical issue shall be obtained as provided in Section 4062.2, and no other medical evaluation shall be obtained. If the employee is not represented by an attorney, the employer shall immediately provide the employee with a form prescribed by the medical director with which to request assignment of a panel of three qualified medical evaluators, the evaluation shall be obtained as provided in Section 4062.1, and no other medical evaluation shall be obtained.

(b) If the employee objects to a decision made pursuant to Section 4610 to modify, delay, or deny a request for authorization of a medical treatment recommendation made by a treating physician, the objection shall be resolved only in accordance with the independent medical review process established in Section 4610.5.

(c) If the employee objects to the diagnosis or recommendation for medical treatment by a physician within the employer's medical provider network established pursuant to Section 4616, the objection shall be resolved only in accordance with the independent medical review process established in Sections 4616.3 and 4616.4.