California Code, Code of Civil Procedure - CCP § 405.39

No order or other action of the court under this chapter shall be appealable. Any party aggrieved by an order made on a motion under this chapter may petition the proper reviewing court to review the order by writ of mandate. The petition for writ of mandate shall be filed and served within 20 days of service of written notice of the order by the court or any party. The court which issued the order may, within the initial 20-day period, extend the initial 20-day period for one additional period not to exceed 10 days. A copy of the petition for writ of mandate shall be delivered to the clerk of the court which issued the order with a request that it be placed in the court file.