CAB/LEG/24.1 Page 11 to enact measures contrary to the provisions of the Convention, provided their application is precisely defined in respect of aim, time and place. Article XVIII Settlement of Disputes Any dispute between the Contracting States relating to the interpretation or application of this Convention which cannot be settled by negotiation, shall at the request of any party be submitted to the Commission of Mediation, Conciliation and Arbitration of the Organization of African Unity. Article XIX Signature and Ratification 1. This Convention shall be open for signature immediately after being approved by the Assembly of Heads of State and Government of the Organization of African Unity. 2. This Convention shall be ratified by each of the Contracting States. The instruments of ratification shall be deposited with the Administrative Secretary General of the Organization of African Unity. Article XX Reservations 1. At the time of signature, ratification or accession, any State may declare its acceptance of this Convention in part only, provided that such reservation may not apply to the provisions of Articles II – XI. 2. Reservations made in conformity with the preceding paragraph shall be deposited together with the instruments of ratification or accession. 3. Any Contracting State which has formulated a reservation in conformity with the preceding paragraph may at any time withdraw it by notifying the Administrative Secretary General of the Organization of African Unity. Article XXI Entry into force 1. This Convention shall come into force on the thirtieth day following the date of deposit of the fourth instrument of ratification or accession with the Administrative Secretary General of the Organization of African Unity, who shall inform participating States accordingly.