Artikel 19

1. This Protocol shall be open for signature by the States signatory to the European Outline Convention on Transfrontier Co-operation between Territorial Communities or Authorities. It shall be subject to ratification, acceptance or approval. A Signatory to this Protocol may not ratify, accept or approve it unless it has previously or simultaneously ratified, accepted or approved the European Outline Convention. Instruments of ratification, acceptance or approval shall be deposited with the Secretary General of the Council of Europe.
2. This Protocol shall enter into force on the first day of the month following expiration of a period of three months after the date of deposit of the fourth instrument of ratification, acceptance or approval.
3. In respect of any Signatory State which subsequently expresses its agreement to be bound by it, the Protocol shall enter into force on the first day of the month following the expiration of a period of three months after the date of deposit of the instrument of ratification, acceptance or approval.