Artikel 25

1. A State which has two or more territorial units in which different systems of law apply in matters of custody of children and of recognition and enforcement of decisions relating to custody may, at the time of signature or when depositing its instrument of ratification, acceptance, approval or accession, declare that this Convention shall apply to all its territorial units or to one or more of them.
2. Such a State may at any later date, by a declaration addressed to the Secretary General of the Council of Europe, extend the application of this Convention to any other territorial unit specified in the declaration. In respect of such territorial unit the Convention shall enter into force on the first day of the month following the expiration of a period of three months after the date of receipt by the Secretary General of such declaration.
3. Any declaration made under the two preceding paragraphs may, in respect of any territorial unit specified in such declaration, be withdrawn by notification addressed to the Secretary General. The withdrawal shall become effective on the first day of the month following the expiration of a period of six months after the date of receipt of such notification by the Secretary General.