9 U.S.C. § 5 : US Code - Section 5: Appointment of arbitrators or umpire

      If in the agreement provision be made for a method of naming or
    appointing an arbitrator or arbitrators or an umpire, such method
    shall be followed; but if no method be provided therein, or if a
    method be provided and any party thereto shall fail to avail
    himself of such method, or if for any other reason there shall be a
    lapse in the naming of an arbitrator or arbitrators or umpire, or
    in filling a vacancy, then upon the application of either party to
    the controversy the court shall designate and appoint an arbitrator
    or arbitrators or umpire, as the case may require, who shall act
    under the said agreement with the same force and effect as if he or
    they had been specifically named therein; and unless otherwise
    provided in the agreement the arbitration shall be by a single