Article 9

1 This Convention shall be open to signature by the member States of the Council of Europe. It shall be subject to ratification, acceptance or approval. Instruments of ratification, acceptance or approval shall be deposited with the Secretary General of the Council of Europe.

2 The Convention shall enter into force three months after the date of the deposit of the fourth instrument of ratification, acceptance or approval, provided that at least two of the States having carried out this formality possess a common frontier.

3 In respect of a signatory State ratifying, accepting or approving subsequently, the Convention shall come into force three months after the date of the deposit of its instrument of ratification, acceptance or approval.