Accession [From Black's Law Dictionary]: Int'l law. A method by which a nation that is not among a treaty's original signatories becomes a party to it <Italy became a party to the nuclear-arms treaty by accession>. See Vienna Convention on the Law of Treaties, art. 15 (1155 U.N.T.S. 331, 8 I.L.M. 679 (1969)). — Also termed adherence; adhesion. See instrument of accession INSTRUMENT OF ACCESSION [From Black's Law]: Int'l law. A document formally acknowledging the issuing state's consent to an existing treaty, and exchanged with the treaty parties or deposited with a designated state or international organization. See accession (3). Succession [From CONVENTION ON SUCCESSION OF STATES IN RESPECT OF TREATIES, 1978]: "succession of States": means the replacement of one State by another in the responsibility for the international relations of territory "predecessor State": means the State which has been replaced by another State on the occurrence of a succession of States "successor State": means the State which has replaced another State on the occurrence of a succession of States "date of the succession of States": means the date upon which the successor State replaced the predecessor State in the responsibility for the international relations of the territory to which the succession of States relates; "newly independent State": means a successor State the territory of which immediately before the date of the succession of States was a dependent territory for the international relations of which the predecessor State was responsible; "notification of succession": means in relation to a multilateral treaty any notification, however phrased or named, made by a successor State expressing its consent to be considered as bound by the treaty