California Code, Labor Code - LAB § 4616.3

(a) If the injured employee notifies the employer of the injury or files a claim for workers' compensation with the employer, the employer shall arrange an initial medical evaluation and begin treatment as required by Section 4600.

(b) The employer shall notify the employee of the existence of the medical provider network established pursuant to this article, the employee's right to change treating physicians within the network after the first visit, and the method by which the list of participating providers may be accessed by the employee.The employer's failure to provide notice as required by this subdivision or failure to post the notice as required by Section 3550 shall not be a basis for the employee to treat outside the network unless it is shown that the failure to provide notice resulted in a denial of medical care.

(c) If an injured employee disputes either the diagnosis or the treatment prescribed by the treating physician, the employee may seek the opinion of another physician in the medical provider network. If the injured employee disputes the diagnosis or treatment prescribed by the second physician, the employee may seek the opinion of a third physician in the medical provider network.