Artikel 27

1. This Agreement shall be open for signature by the member States of the Council of Europe which have already expressed their consent to be bound by the Vienna Convention. They may express their consent to be bound by this Agreement by:
a. signature without reservation as to ratification, acceptance or approval; or
b. signature subject to ratification, acceptance or approval, followed by ratification, acceptance or approval.
2. Instruments of ratification, acceptance or approval shall be deposited with the Secretary General of the Council of Europe.
3. This Agreement shall enter into force on the first day of the month following the expiry of a period of three months after the date on which three member States of the Council of Europe have expressed their consent to be bound by the Agreement in accordance with the provisions of paragraph 1.
4. In respect of any signatory State which subsequently expresses its consent to be bound by it, the Agreement shall enter into force on the first day of the month following the expiry of a period of three months after the date of its consent to be bound by the Agreement in accordance with the provisions of paragraph 1.