180 2. If, for some special reason, a member of the Tribunal considers that he should not take part in the decision of a particular case, he shall so inform the President of the Tribunal. 3. If the President considers that for some special reason one of the members of the Tribunal should not sit in a particular case, he shall give him notice accordingly. 4. Any doubt on these points shall be resolved by decision of the majority of the other members of the Tribunal present. Article 9 Consequence of ceasing to fulfil required conditions If, in the unanimous opinion of the other members of the Tribunal, a member has ceased to fulfil the required conditions, the President of the Tribunal shall declare the seat vacant. Article 10 Privileges and immunities The members of the Tribunal, when engaged on the business of the Tribunal, shall enjoy diplomatic privileges and immunities. Article 11 Solemn declaration by members Every member of the Tribunal shall, before taking up his duties, make a solemn declaration in open session that he will exercise his powers impartially and conscientiously. Article 12 President, Vice-President and Registrar 1. The Tribunal shall elect its President and Vice-President for three years; they may be re-elected. 2. The Tribunal shall appoint its Registrar and may provide for the appointment of such other officers as may be necessary. 3. The President and the Registrar shall reside at the seat of the Tribunal. Article 13 Quorum 1. All available members of the Tribunal shall sit; a quorum of 11 elected members shall be required to constitute the Tribunal. 2. Subject to article 17 of this Annex, the Tribunal shall determine which members are available to constitute the Tribunal for the consideration of a particular dispute, having regard to the effective functioning of the chambers as provided for in articles 14 and 15 of this Annex. 3. All disputes and applications submitted to the Tribunal shall be heard and determined by the Tribunal, unless article 14 of this Annex applies, or the parties request that it shall be dealt with in accordance with article 15 of this Annex.