All the 33 States of Latin America and the Caribbean are Parties to the Treaty of Tlatelolco and, as such, Members of OPANAL.

Article 29, paragraph 1, of the Treaty of Tlatelolco (amended) provides that the instrument shall enter into force among the States that have ratified it as soon as the following requirements have been met:

a. Deposit of the instruments of ratification of this Treaty with the Depositary Government by the Governments of the States mentioned in article 26 which are in existence on the date when this Treaty is opened for signature and which are not affected by the provisions of article 26, paragraph 2;

b. Signature and ratification of Additional Protocol I annexed to this Treaty, by all extracontinental and continental States having de jure or de facto international responsibility for territories situated in the zone of application of the Treaty;

c. Signature and ratification of the Additional Protocol II annexed to this Treaty, by all powers possessing nuclear weapons;

d. Conclusion of bilateral agreements on the application of the Safeguards System of the International Atomic Energy Agency in accordance with article 13 of this Treaty.

Meanwhile, paragraph 2 of Article 29 of the Treaty of Tlatelolco stipulates that:

All Signatory States shall have the imprescriptible right to waive, wholly or in part, the requirements laid down in the preceding paragraph. They may do so by means of a declaration which shall be annexed to their respective instrument of ratification and which may be formulated at the time of deposit of the instrument or subsequently. For those States which exercise this right, this Treaty shall enter into force upon deposit of the declaration, or as soon as those requirements have been met which have not been expressly waived.