1. A regional economic integration organization that is constituted by sovereign States and has competence over certain matters governed by this Convention may similarly sign, ratify, accept, approve or accede to this Convention. The regional economic integration organization shall in that case have the rights and obligations of a Contracting State, to the extent that that organization has competence over matters governed by this Convention. Where the number of Contracting States is relevant in this Convention, the regional economic integration organization shall not count as a Contracting State in addition to its member States that are Contracting States. 2. The regional economic integration organization shall, at the time of signature, ratification, acceptance, approval or accession, make a declaration to the depositary specifying the matters governed by this Convention in respect of which competence has been transferred to that organization by its member States. The regional economic integration organization shall promptly notify the depositary of any changes to the distribution of competence, including new transfers of competence, specified in the declaration under this paragraph. 3. Any reference to a “Contracting State” or “Contracting States” in this Convention applies equally to a regional economic integration organization where the context so requires. 4. This Convention shall not prevail over any conflicting rules of any regional economic integration organization as applicable to parties whose respective places of business are located in States members of any such organization, as set out by declaration made in accordance with article 21. Article 18 Effect in domestic territorial units 1. If a Contracting State has two or more territorial units in which different systems of law are applicable in relation to the matters dealt with in this Convention, it may, at the time of signature, ratification, acceptance, approval or accession, declare that this Convention is to extend to all its territorial units or only to one or more of them, and may amend its declaration by submitting another declaration at any time. 2. These declarations are to be notified to the depositary and are to state expressly the territorial units to which the Convention extends. 3. If, by virtue of a declaration under this article, this Convention extends to one or more but not all of the territorial units of a Contracting State, and if the place of business of a party is located in that State, this place of business, for the purposes of this Convention, is considered not to be in a Contracting State, unless it is in a territorial unit to which the Convention extends. 4. If a Contracting State makes no declaration under paragraph 1 of this article, the Convention is to extend to all territorial units of that State. Article 19 30