3. This Convention is subject to ratification, acceptance or approval. Instruments of ratification, acceptance or approval shall be deposited with the Secretary-General of the United Nations. A regional economic integration organization may deposit its instrument of ratification, acceptance or approval if at least one of its member States has done likewise. In that instrument of ratification, acceptance or approval, such organization shall declare the extent of its competence with respect to the matters governed by this Convention. Such organization shall also inform the depositary of any relevant modification in the extent of its competence. 4. This Convention is open for accession by any State or any regional economic integration organization of which at least one member State is a Party to this Convention. Instruments of accession shall be deposited with the Secretary-General of the United Nations. At the time of its accession, a regional economic integration organization shall declare the extent of its competence with respect to matters governed by this Convention. Such organization shall also inform the depositary of any relevant modification in the extent of its competence. Article 37. Relation with protocols 1. This Convention may be supplemented by one or more protocols. 2. In order to become a Party to a protocol, a State or a regional economic integration organization must also be a Party to this Convention. 3. A State Party to this Convention is not bound by a protocol unless it becomes a Party to the protocol in accordance with the provisions thereof. 4. Any protocol to this Convention shall be interpreted together with this Convention, taking into account the purpose of that protocol. Article 38. Entry into force 1. This Convention shall enter into force on the ninetieth day after the date of deposit of the fortieth instrument of ratification, acceptance, approval or accession. For the purpose of this paragraph, any instrument deposited by a regional economic integration organization shall not be counted as additional to those deposited by member States of such organization. 2. For each State or regional economic integration organization ratifying, accepting, approving or acceding to this Convention after the deposit of the 37