California Code, Labor Code - LAB § 1504

(a) An employer shall, upon expiration of a leave authorized by this part, restore an employee to the position held by him or her when the leave began or to a position with equivalent seniority status, employee benefits, pay, and other terms and conditions of employment. An employer may decline to restore an employee as required in this subdivision because of conditions unrelated to the exercise of rights under this part by the employee.

(b) An employer and an employee may negotiate for the employer to maintain the benefits of the employee at the expense of the employer during the leave.