At its fifty-second session, in 2000, the Commission, on the basis of the recommendation of a Working Group on the long-term programme of work, concluded that the topic “Risks ensuing from fragmentation of international law” was appropriate for inclusion in its long-term programme of work. [2]  The Commission noted that this topic was different from the other topics which it had considered. Nevertheless, the Commission expressed the view that it could contribute to a better understanding of the increasingly important issues involved in the topic. The Commission also noted that the method and outcome of work on the topic did not fall strictly within the normal form of codification, but was well within its competence and in accordance with its Statute. [3]

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

The General Assembly, in resolution 55/152 of 12 December 2000 (E, F, S, R, C, A), took note of the Commission’s report concerning its long-term programme of work. In resolution 56/82 of 12 December 2001 (E, F, S, R, C, A), the Assembly requested the Commission to further consider the topic, having due regard to comments made by Governments.

At its fifty-fourth session, in 2002, the Commission decided to include the topic “Fragmentation of international law: difficulties arising from the diversification and expansion of international law” in its programme of work and to establish a Study Group on the topic, chaired by Bruno Simma. [4]  In its report, [5]  the Study Group made the following recommendations: to amend the title of the topic to its present wording; to prepare a series of studies on specific aspects of the topic to assist international judges and practitioners in coping with the consequences of the diversification of international law; [6]  and to provide a “toolbox” designed to assist in solving practical problems arising from incongruities and conflicts between existing legal norms and regimes. The Study Group recommended that the following topics could be the subject of study: (a) the function and scope of the lex specialis rule and the question of “self-contained regimes”; (b) the interpretation of treaties in the light of “any relevant rules of international law applicable in the relations between the parties” (article 31 (3) (c) of the Vienna Convention on the Law of Treaties (see annex V, section F)), in the context of general developments in international law and concerns of the international community; (c) the application of successive treaties relating to the same subject matter (article 30 of the Vienna Convention on the Law of Treaties); (d) the modification of multilateral treaties between certain of the parties only (article 41 of the Vienna Convention on the Law of Treaties); and (e) hierarchy in international law: jus cogens, obligations erga omnes, Article 103 of the Charter of the United Nations, as conflict rules. As a first step, the Study Group recommended requesting its Chairman to undertake a study on subject (a) above. The Study Group noted that the choice of subjects for study was guided by the Commission’s previous work relating to the law of treaties and the responsibility of States for internationally wrongful acts and that the Commission’s work on the present topic would build upon and further develop its earlier texts. [7]  The Commission adopted the report of the Study Group. [8]

The General Assembly, in resolution 57/21 of 19 November 2002 (E, F, S, R, C, A), took note of the Commission’s decision to include the topic in its programme of work.

At its fifty-fifth session, in 2003, the Commission appointed Martti Koskenniemi as Chairman of the Study Group, to succeed Bruno Simma who had resigned from the Commission. [9]  The Study Group established a tentative schedule of work for the remainder of the quinquennium (2004-2006), agreed upon the distribution among its members of the preparation of the studies on the remaining subjects approved by the Commission in 2002, decided upon the methodology to be adopted for the preparation of the studies, and held a preliminary discussion of an outline prepared by the new Chairman of the Study Group on the first subject identified for study, namely, “The function and scope of the lex specialis rule and the question of self-contained regimes”. The Study Group also indicated its intention to prepare a final study covering all topics which may include the elaboration of guidelines. [10]  The Commission took note of the report of the Study Group. [11]

At its fifty-sixth session, in 2004, the Commission reconstituted the Study Group. [12] It held discussions on the study on the “Function and scope of the lex specialis rule and the question of ‘self-contained regimes’”, as well as discussions on the outlines prepared in respect of the other remaining studies. The Commission took note of the report of the Study Group. [13]

At its fifty-seventh session, in 2005, the Study Group was again reconstituted. [14] It had before it the following: (a) a memorandum on regionalism in the context of the study on “the function and scope of the lex specialis rule and the question of self-contained regimes”; (b) a study on the interpretation of treaties in the light of “any relevant rules of international law applicable in the relations between the parties” (article 31 (3) (c) of the Vienna Convention on the Law of Treaties), in the context of general developments in international law and concerns of the international community; (c) a study on the application of successive treaties relating to the same subject matter (article 30 of the Vienna Convention on the Law of Treaties); (d) a study on the modification of multilateral treaties between certain of the parties only (article 41 of the Vienna Convention on the Law of Treaties); and (e) a study on hierarchy in international law: jus cogens, obligations erga omnes, Article 103 of the Charter of the United Nations, as conflict rules. The Study Group also had an informal paper on the “Disconnection Clause”. The Commission took note of the report of the Study Group. [15]

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