The Commission considered the sub-topic at its twentieth, twenty-second, twenty-fourth and twenty-sixth sessions, in 1968, 1970, 1972 and 1974, respectively. The Commission appointed Sir Humphrey Waldock and Sir Francis Vallat as the successive Special Rapporteurs for the sub-topic at its nineteenth and twenty-fifth sessions, in 1967 and 1973, respectively. In connection with its consideration of the topic, the Commission had before it the reports of the Special Rapporteurs, [1]  information provided by Governments and international organizations [2]  as well as documents prepared by the Secretariat. [3]

Extracts from The Work of the International Law Commission, 6th ed., vol. 1

At its twenty-fourth session, in 1972, the Commission conducted the first reading of the draft articles on succession of States in respect of treaties. At that session, the Commission adopted on first reading a provisional draft with commentaries and, in accordance with articles 16 and 21 of its Statute, decided to transmit it to Governments of Member States for their observations.

The General Assembly, in resolution 2926 (XXVII) of 28 November 1972 (E, F, S, R, C, A), recommended that the Commission should continue its work on the sub-topic in the light of comments received from Member States on the provisional draft. In resolution 3071 (XXVIII) of 30 November 1973 (E, F, S, R, C, A), the General Assembly recommended that the Commission complete at its twenty-sixth session, in 1974, the second reading of the draft on succession of States in respect of treaties, in the light of comments received from Member States.

At its twenty-sixth session, in 1974, the Commission adopted the final text of the draft articles on the succession of States in respect of treaties, with commentaries, [4]  and submitted it to the General Assembly with a recommendation that the General Assembly should invite Member States to submit their written comments and observations on the draft articles and should convene a conference of plenipotentiaries to study the draft articles and conclude a convention on the subject. [5]

The General Assembly, in resolution 3315 (XXIX) of 14 December 1974 (E, F, S, R, C, A), invited Member States to submit their written comments and observations on the draft articles prepared by the Commission and on the procedure by which and the form in which work on the draft articles should be completed. The following year, the Assembly, by resolution 3496 (XXX) of 15 December 1975 (E, F, S, R, C, A), decided to convene a conference of plenipotentiaries in 1977 to consider the draft articles and to embody the results of its work in an international convention and such other instruments as it might deem appropriate. In the resolution, the Assembly urged Member States which had not yet done so to submit as soon as possible their written comments and observations on the draft articles. On 24 November 1976, the Assembly adopted resolution 31/18 (E, F, S, R, C, A) by which it decided that the United Nations Conference on Succession of States in Respect of Treaties would be held from 4 April to 6 May 1977 at Vienna.

The Conference was held as scheduled but, having been unable to conclude its work in the time available, it recommended on 6 May 1977 that the General Assembly decide to reconvene the Conference in the first half of 1978 for a final session. [6]

The resumed session of the Conference, approved by General Assembly resolution 32/47 of 8 December 1977 (E, F, S, R, C, A) , was held at Vienna from 31 July to 23 August 1978. [7]

The delegations of one hundred States participated in the Conference (eighty-nine States in the 1977 session and ninety-four States in the resumed session). Two States were represented by observers at each of the 1977 and resumed sessions. In addition, the United Nations Council for Namibia [8]  participated in the Conference and the Palestine Liberation Organization and the South West Africa People’s Organization (SWAPO) were represented by observers, SWAPO at the 1977 session only. Four specialized and related agencies and one other intergovernmental organization sent observers to the 1977 session and two other intergovernmental organizations to both the 1977 and resumed sessions.

The Conference assigned to a Committee of the Whole the consideration of the draft articles adopted by the International Law Commission and entrusted to a Drafting Committee, in addition to its responsibilities for drafting and coordinating and reviewing all texts adopted, with the preparation of the title, preamble and final clauses of the Convention and the Final Act of the Conference. The Conference also established an Informal Consultations Group for the purpose of considering draft articles 6, 7 and 12 and, at the resumed session, an Ad hoc Group on Peaceful Settlement of Disputes. The Conference, on 22 August 1978, adopted the Vienna Convention on Succession of States in Respect of Treaties [9]  consisting of a preamble, fifty articles and an annex. The Convention retains, to a considerable degree, the structure and the text of the draft articles adopted by the International Law Commission. The annex to the Convention specifies the conciliation procedure to which article 42 of the Convention relates.

The Final Act of the Conference, of which five resolutions adopted by the Conference form an integral part, was signed on 23 August 1978. The Convention was opened for signature on 23 August 1978 until 28 February 1979 at the Federal Ministry for Foreign Affairs of the Republic of Austria and, subsequently, until 31 August 1979 at United Nations Headquarters. Signatures are subject to ratification. The Convention remains open for accession by any State. The Convention entered into force on 6 November 1996.

Of the five resolutions adopted by the Conference, one, relating to incompatible treaty obligations and rights arising from a uniting of States, recommends that in such cases the successor States and the other States parties to the treaties in question make every effort to resolve the matter by mutual agreement. In another resolution, concerning Namibia, the Conference resolved that the relevant articles of the Convention shall be interpreted, in the case of Namibia, in conformity with United Nations resolutions on the question of Namibia and that South Africa was not the predecessor State of the future independent State of Namibia. [10]

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