By decision of the appointing authority in the interests of the service, officials shall be transferred periodically, if necessary without regard to vacant posts. Posts to be filled by officials serving outside the Community need not be declared vacant until the transfer procedure referred to in the first subparagraph ("the mobility procedure") has been completed. ... In order to allow retraining periods of limited duration as part of the mobility procedure provided for in Article 2, the appointing authority may decide to assign an official serving outside the Community to a post in a Member State of the European Communities; such assignments, which shall not be preceded by a vacancy notice, may not be for more than four years. ... An official shall carry out his duties at the place to which he is assigned on recruitment or on transfer in the interests of the service following the mobility procedure.
