Cal. Code of Civil Procedure § 1282

Unless the arbitration agreement otherwise provides, or unless the parties to the arbitration otherwise provide by an agreement which is not contrary to the arbitration agreement as made or as modified by all of the parties thereto: (a) The arbitration shall be by a single neutral arbitrator. (b) If there is more than one arbitrator, the powers and duties of the arbitrators, other than the powers and duties of a neutral arbitrator, may be exercised by a majority of them if reasonable notice of all proceedings has been given to all arbitrators. (c) If there is more than one neutral arbitrator: (1) The powers and duties of a neutral arbitrator may be exercised by a majority of the neutral arbitrators. (2) By unanimous agreement of the neutral arbitrators, the powers and duties may be delegated to one of their number but the power to make or correct the award may not be so delegated. (d) If there is no neutral arbitrator, the powers and duties of a neutral arbitrator may be exercised by a majority of the arbitrators.