[s] What is the difference between signing, ratifying and acceding to a Hague Convention?

By signing a Hague Convention, a State expresses, in principle, its intention to become a Party to the Convention. However, signature does not, in any way, oblige a State to take further action (towards ratification or not).

Ratification involves the legal obligation for the ratifying State to apply the Convention. According to the Hague Conference's terminology, ratification is, in general, reserved for Member States exclusively. There are, however, some exceptions. These include the Convention of 22 December 1986 on the Law Applicable to Contracts for the International Sale of Goods, which is open for signature and ratification by all States with no distinction, and the Convention of 29 May 1993 on Protection of Children and Co-operation in Respect of Intercountry Adoption, which is open for signature and ratification by all States that have participated in the Seventeenth Session.

Others States wishing to become a Party to a Hague Convention may accede. This, however, is only possible once the Convention has entered into force. The States that are already Parties to the Convention must in some cases accept this accession. This system of acceptance varies from one Convention to another: some Conventions provide for a system of tacit acceptance (if there is no opposition over a certain period of time; see e.g. Art. 58 (3) of the 1996 Convention on Jurisdiction, Applicable Law, Recognition, Enforcement and Co-operation in Respect of Parental Responsibility and Measures for the Protection of Children), whereas others require express acceptance by the States Parties to the Convention (see e.g. Art. 38 (4) of the 1980 Convention on the Civil Aspects of International Child Abduction). It should be noted that the Convention of 22 December 1986 on the Law Applicable to Contracts for the International Sale of Goods provides that every State (including Member States of the Conference) may accede to this Convention.