CA Lab Code Section 3859

(a)

No release or settlement of any claim under this chapter as to either the employee or the employer is valid without the written consent of both. Proof of service filed with the court is sufficient in any action or proceeding where such approval is required by law.

(b)

Notwithstanding anything to the contrary contained in this chapter, an employee may settle and release any claim he may have against a third party without the consent of the employer. Such settlement or release shall be subject to the employer’s right to proceed to recover compensation he has paid in accordance with Section 3852.