At its forty-fifth session, in 1993, the International Law Commission, on the basis of the recommendation of a Working Group on the long-term programme of work, decided to include in the Commission's agenda, subject to the approval of the General Assembly, the topic "The law and practice relating to reservations to treaties". The Commission noted that the 1969 Vienna Convention on the Law of Treaties, the 1978 Vienna Convention on Succession of States in Respect of Treaties and the 1986 Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations set out some principles concerning reservations to treaties, but they did so in terms that were too general to act as a guide for State practice and left a number of important matters in the dark. These conventions provide ambiguous answers to the questions of differentiating between reservations and declarations of interpretation, the scope of declarations of interpretation, the validity of reservations (the conditions for the lawfulness of reservations and their applicability to another State) and the regime of objections to reservations (in particular, the admissibility and scope of objections to a reservation which is neither prohibited by the treaty nor contrary to its object and purpose). These conventions are also silent on the effect of reservations on the entry into force of treaties, problems pertaining to the particular object of some treaties (in particular the constituent instruments of international organizations and human rights treaties), reservations to codification treaties and problems resulting from particular treaty techniques (elaboration of additional protocols, bilateralization techniques). The Commission recognized the need not to challenge the regime established in articles 19 to 23 of the 1969 Vienna Convention on the Law of Treaties, but nonetheless considered that these provisions could be clarified and developed in draft protocols to existing conventions or a guide to practice. [2]

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

The General Assembly, in resolution 48/31 of 9 December 1993 (E, F, S, R, C, A), endorsed the above decision of the International Law Commission on the understanding that the final form to be given to the work on the topic would be decided after a preliminary study was presented to the Assembly.

At its forty-sixth session, in 1994, the Commission appointed Mr. Alain Pellet as Special Rapporteur for the topic. [3]  

The General Assembly, in resolution 49/51 of 9 December 1994 (E, F, S, R, C, A), again endorsed the decision of the Commission on the understanding reflected above.

At its forty-seventh session, in 1995, the Commission had before it the first report [4]  of the Special Rapporteur. This preliminary report provided a detailed study of the Commission’s previous work on reservations and its outcome. It also provided an inventory of the problematic aspects of the topic including those relating to the ambiguities and gaps in the provisions concerning reservations contained in the Vienna Conventions on the Law of Treaties, as well as those connected with the specific object of certain treaties or provisions or arising from certain specific treaty approaches. Finally, it outlined the scope and form of the Commission’s future work, guided by the preservation of what had been achieved, and proposed the form that the results of the Commission’s work might take. Following the Commission’s consideration of the report, the Special Rapporteur summarized the conclusions he had drawn with respect to: (1) the title of the topic, which should now read “Reservations to treaties”; (2) the form of the results of the study, which should be a guide to practice in respect of reservations; (3) the flexible way in which the Commission’s work on the topic should be carried out; and (4) the consensus in the Commission that there should be no change in the relevant provisions of the Vienna Conventions. The Guide to Practice in the form of draft articles with commentaries would provide guidelines for the practice of States and international organizations in respect of reservations. These guidelines would, if necessary, be accompanied by model clauses. [5]  In the view of the Commission, those conclusions constituted the results of the preliminary study requested by the General Assembly in resolutions 48/31 of 9 December 1993 and 49/51 of 9 December 1994. [6]  The Commission authorized the Special Rapporteur to prepare a detailed questionnaire on reservations to treaties to ascertain the practice of, and the problems encountered by, States and international organizations, particularly those which are depositaries of multilateral conventions. [7]

The General Assembly, in resolution 50/45 of 11 December 1995 (E, F, S, R, C, A), took note of the Commission’s conclusions, invited the Commission to continue its work along the lines indicated in its report and invited States and international organizations, particularly those which are depositaries, to answer the questionnaire.

At its forty-eighth session, in 1996, the Commission had before it the Special Rapporteur’s second report [8]  as well as a bibliography. [9]  The report dealt with the issue of the unity or diversity of the legal regime of reservations to treaties, especially reservations to human rights treaties. The Special Rapporteur concluded that despite the diversity of treaties, the Vienna regime on reservations is generally applicable. Moreover, the coexistence of monitoring mechanisms does not preclude monitoring bodies from making determinations of the permissibility of reservations, even if States still can draw any consequences they wish from such determinations and react accordingly. The Special Rapporteur also proposed a draft resolution of the International Law Commission on reservations to normative multilateral treaties, including human rights treaties, which was addressed to the General Assembly for the purpose of drawing attention to and clarifying the legal aspects of the matter. The Commission did not have time to consider the report and the draft resolution. The Commission therefore deferred the debate on the topic to its next session. [10]

At its forty-ninth session, in 1997, the Commission again had before it the second report of the Special Rapporteur on the topic concerning the question of the unity or diversity of the juridical regime for reservations. Wishing to contribute to discussions taking place in other forums on the subject of reservations to normative multilateral treaties, particularly human rights treaties, the Commission adopted a number of preliminary conclusions on the subject. [11]  The Commission welcomed comments by Governments on these preliminary conclusions and invited monitoring bodies set up by the relevant human rights treaties to submit their comments as well. [12]

The General Assembly, in resolution 52/156 of 15 December 1997 (E, F, S, R, C, A), took note of the Commission’s preliminary conclusions and its invitation to all treaty bodies set up by normative multilateral treaties that might wish to do so to provide, in writing, their comments and observations on the conclusions, while drawing the attention of Governments to the importance for the International Law Commission of having their views on the preliminary conclusions.

At its fiftieth session, in 1998, the Commission had before it the Special Rapporteur’s third report, [13]  which dealt with the definition of reservations and interpretative declarations to treaties. The report focused on the distinction between reservations and interpretative declarations, the uncertainties of the terminology and the criteria for the distinction between the two categories. The report also dealt with the issue of “reservations” (and interpretative declarations) in respect of bilateral treaties in the light of theory and State practice. The Special Rapporteur proposed the following draft guidelines: 1.1 (Definition of reservations), 1.1.1 (Joint formulation of a reservation), 1.1.2 (Moment when a reservation is formulated), 1.1.3 (Reservations formulated when notifying territorial application), 1.1.4 (Object of reservations), 1.1.5 (Statements designed to increase the obligations of their author), 1.1.6 (Statements designed to limit the obligations of their author), 1.1.7 (Reservations relating to non-recognition), 1.1.8 (Reservations having territorial scope), 1.1.9 (“Reservations” to bilateral treaties), 1.2 (Definition of interpretative declarations), 1.2.1 (Joint formulation of interpretative declarations), 1.2.2 (Phrasing and name), 1.2.3 (Formulation of an interpretative declaration when a reservation is prohibited), 1.2.4 (Conditional interpretative declarations), 1.2.5 (General declarations of policy), 1.2.6 (Informative declarations), 1.2.7 (Interpretative declarations in respect of bilateral treaties), 1.2.8 (Legal effect of acceptance of an interpretative declaration made in respect of a bilateral treaty by the other party), 1.3.1 (Method of distinguishing between reservations and interpretative declarations) and 1.4 (Scope of definitions). The Special Rapporteur also tentatively proposed the following draft guidelines concerning the distinction between reservations and interpretative declarations: 1.3.0 (Criterion of reservations), 1.3.0 bis (Criterion of interpretative declarations) and 1.3.0 ter (Criterion of conditional interpretative declarations). After considering part of the report, the Commission referred draft guidelines 1.1, 1.1.1-1.1.8, 1.2 and 1.4 to the Drafting Committee. [14]

At the same session, the Commission provisionally adopted the following seven draft guidelines as well as the commentaries thereto: 1.1 (Definition of reservations), 1.1.1 [1.1.4] [15]  (Object of reservations), 1.1.2 (Instances in which reservations may be formulated), 1.1.3 [1.1.8] (Reservations having territorial scope), 1.1.4 [1.1.3] (Reservations formulated when notifying territorial application), 1.1.7 [1.1.1] (Joint formulation of a reservation) and a draft guideline with no title or number concerning the relation between the definition and the permissibility of reservations. [16]

At its fifty-first session, in 1999, the Commission again had before it part of the Special Rapporteur’s third report, which it had not had time to consider at its fiftieth session, the fourth report on the topic [17]  as well as a revised bibliography. [18]  In the fourth report, the Special Rapporteur continued the consideration of the definition of reservations and interpretative declarations and proposed a revised version of draft guideline 1.1.7 (1.1.7 bis) (Statements of non-recognition) which was already before the Drafting Committee. After considering the reports, the Commission referred draft guidelines 1.1.9 (“Reservations” to bilateral treaties), 1.2.1 (Joint formulation of interpretative declarations), 1.2.2 (Phrasing and name), 1.2.3 (Formulation of an interpretative declaration when a reservation is prohibited), 1.2.4 (Conditional interpretative declarations), 1.2.5 (General statements of policy), 1.2.6 (Informative declarations), 1.2.7 (Interpretative declarations in respect of bilateral treaties), 1.2.8 (Legal effect of acceptance of an interpretative declaration made in respect of a bilateral treaty by the other party) and 1.3.1 (Method of distinguishing between reservations and interpretative declarations) to the Drafting Committee. The Commission noted that draft guidelines 1.3.0, 1.3.0 bis and 1.3.0 ter concerning the distinction between reservations and interpretative declarations were tentatively proposed by the Special Rapporteur for the purpose of determining a series of criteria stemming from the general definitions of reservations and interpretative declarations. The Commission concluded that the criteria were inherent in the definitions and that these three draft guidelines did not add a new element. The Commission decided not to refer those guidelines to the Drafting Committee but to reflect their content in the relevant commentaries to draft guidelines on this issue. [19]

At the same session, the Commission provisionally adopted the following eighteen draft guidelines as well as the commentaries thereto: 1.1.5 [1.1.6] (Statements purporting to limit the obligations of their author), 1.1.6 (Statements purporting to discharge an obligation by equivalent means), 1.2 (Definition of interpretative declarations), 1.2.1 [1.2.4] (Conditional interpretative declarations), 1.2.2 [1.2.1] (Interpretative declarations formulated jointly), 1.3 (Distinction between reservations and interpretative declarations), 1.3.1 (Method of implementation of the distinction between reservations and interpretative declarations), 1.3.2 [1.2.2] (Phrasing and name), 1.3.3 [1.2.3] (Formulation of a unilateral statement when a reservation is prohibited), 1.4 (Unilateral statements other than reservations and interpretative declarations), 1.4.1 [1.1.5] (Statements purporting to undertake unilateral commitments), 1.4.2 [1.1.6] (Unilateral statements purporting to add further elements to a treaty), 1.4.3 [1.1.7] (Statements of non-recognition), 1.4.4 [1.2.5] (General statements of policy), 1.4.5 [1.2.6] (Statements concerning modalities of implementation of a treaty at the internal level), 1.5.1 [1.1.9] (Reservations to bilateral treaties), 1.5.2 [1.2.7] (Interpretative declarations in respect of bilateral treaties) and 1.5.3 [1.2.8] (Legal effect of acceptance of an interpretative declaration made in respect of a bilateral treaty by the other party). In the light of the consideration of interpretative declarations, the Commission also adopted a new version of draft guideline 1.1.1 [1.1.4] (Object of reservations) and of the draft guideline without a title or number (which has become draft guideline 1.6 (Scope of definitions)). [20]

At its fifty-second session, in 2000, the Commission had before it the Special Rapporteur’s fifth report, [21]  which dealt, on the one hand, with the alternatives to reservations and interpretative declarations and, on the other hand, with the procedure regarding reservations and interpretative declarations, particularly their formulation and the question of late reservations and interpretative declarations. The Commission was able to consider only the first part of the fifth report [22]  in which the Special Rapporteur proposed the following draft guidelines: 1.1.8 (Reservations formulated under exclusionary clauses), 1.4.6 (Unilateral statements adopted under an optional clause), 1.4.7 (Restrictions contained in unilateral statements adopted under an optional clause), 1.4.8 (Unilateral statements providing for a choice between the provisions of a treaty), 1.7.1 (Alternatives to reservations), 1.7.2 (Different procedures permitting modification of the effects of the provisions of a treaty), 1.7.3 (Restrictive clauses), 1.7.4 ([“Bilateralized reservations”] [Agreements between States having the same object as reservations]) and 1.7.5 (Alternative to interpretative declarations). After considering the first part of the report, the Commission referred the proposed draft guidelines to the Drafting Committee. [23]

At the same session, the Commission provisionally adopted the following five draft guidelines as well as the commentaries thereto: 1.1.8 (Reservations made under exclusionary clauses), 1.4.6 [1.4.6, 1.4.7] (Unilateral statements made under an optional clause), 1.4.7 [1.4.8] (Unilateral statements providing for a choice between the provisions of a treaty), 1.7.1 [1.7.1, 1.7.2, 1.7.3, 1.7.4] (Alternatives to reservations) and 1.7.2 [1.7.5] (Alternatives to interpretative declarations). [24]  The Commission deferred consideration of the second part of the fifth report to the following session. [25]  

At its fifty-third session, in 2001, the Commission again had before it the second part of the fifth report [26]  relating to questions of procedure regarding reservations and interpretative declarations. The Special Rapporteur proposed the following draft guidelines: 2.2.1 (Reservations formulated when signing and formal confirmation), 2.2.2 (Reservations formulated when negotiating, adopting or authenticating the text of the treaty and formal confirmation), 2.2.3 (Non-confirmation of reservations formulated when signing [an agreement in simplified form] [a treaty that enters into force solely by being signed]), 2.2.4 (Reservations formulated when signing for which the treaty makes express provision), 2.3.1 (Reservations formulated late), 2.3.2 (Acceptance of reservations formulated late), 2.3.3 (Objection to reservations formulated late), 2.3.4 (Late exclusion or modification of the legal effects of a treaty by procedures other than reservations), 2.4.3 (Times at which an interpretative declaration may be formulated), 2.4.4 (Conditional interpretative declarations formulated when negotiating, adopting or authenticating or signing the text of the treaty and formal confirmation), 2.4.5 (Non-confirmation of interpretative declarations formulated when signing [an agreement in simplified form] [a treaty that enters into force solely by being signed]), 2.4.6 (Interpretative declarations formulated when signing for which the treaty makes express provision), 2.4.7 (Interpretative declarations formulated late) and 2.4.8 (Conditional interpretative declarations formulated late). After considering the report, the Commission referred the proposed draft guidelines to the Drafting Committee. [27]

At the same session, the Commission provisionally adopted the following twelve draft guidelines as well as the commentaries thereto: 2.2.1 (Formal confirmation of reservations formulated when signing a treaty), 2.2.2 [2.2.3] (Instances of non-requirement of confirmation of reservations formulated when signing a treaty), 2.2.3 [2.2.4] (Reservations formulated upon signature when a treaty expressly so provides), 2.3.1 (Late formulation of a reservation), 2.3.2 (Acceptance of the late formulation of a reservation), 2.3.3 (Objection to the late formulation of a reservation), 2.3.4 (Subsequent exclusion or modification of the legal effects of a treaty by means other than reservations), 2.4.3 (Time at which an interpretative declaration may be formulated), 2.4.4 [2.4.5] (Non-requirement of confirmation of interpretative declarations made when signing a treaty), 2.4.5 [2.4.4] (Formal confirmation of conditional interpretative declarations formulated when signing a treaty), 2.4.6 [2.4.7] (Late formulation of an interpretative declaration) and 2.4.7 [2.4.8] (Late formulation of a conditional interpretative declaration). [28]

At the fifty-third session, the Commission also had before it the Special Rapporteur’s sixth report [29]  relating to the modalities of formulating reservations and interpretative declarations (including their form and notification) as well as the publicity of reservations and interpretative declarations (their communication, addressees and obligations of depositaries). The Special Rapporteur proposed the following draft guidelines: 2.1.1 (Written form), 2.1.2 (Form of formal confirmation), 2.1.3 (Competence to formulate a reservation at the international level), 2.1.3 bis (Competence to formulate a reservation at the internal level), 2.1.4 (Absence of consequences at the international level of the violation of internal rules regarding the formulation of reservations), 2.1.5 (Communication of reservations), 2.1.6 (Procedure for communication of reservations), 2.1.7 (Functions of depositaries), 2.1.8 (Effective date of communications relating to reservations), 2.4.1 (Formulation of interpretative declarations), 2.4.1 bis (Competence to formulate an interpretative declaration at the internal level), 2.4.2 (Formulation of conditional interpretative declarations) and 2.4.9 (Communication of conditional interpretative declarations). After considering the report, the Commission referred the proposed guidelines to the Drafting Committee. [30]

At its fifty-fourth session, in 2002, the Commission had before it the Special Rapporteur’s seventh report [31]  relating to the formulation, modification and withdrawal of reservations and interpretative declarations. The Special Rapporteur proposed the following draft guidelines: draft guidelines: 2.1.7 bis (Case of manifestly impermissible reservations), 2.5.1 (Withdrawal of reservations), 2.5.2 (Form of withdrawal), 2.5.3 (Periodic review of the usefulness of reservations), 2.5.4 (Withdrawal of reservations held to be impermissible by a body monitoring the implementation of a treaty), three alternative versions of guideline 2.5.5 (Competence to withdraw a reservation at the international level; the third version entitled “Competence to withdraw a reservation”), 2.5.5 bis (Competence to withdraw a reservation at the internal level), 2.5.5 ter (Absence of consequences at the international level of the violation of internal rules regarding the withdrawal of reservations), two alternative versions of guideline 2.5.6 (Communication of withdrawal of a reservation), 2.5.6 bis (Procedure for communication of withdrawal of reservations), 2.5.6 ter (Functions of depositaries), 2.5.7 (Effect of withdrawal of a reservation), 2.5.8 (Effect of withdrawal of a reservation in cases of objection to the reservation and opposition to entry into force of the treaty with the reserving State or international organization), 2.5.9 (Effective date of withdrawal of a reservation, including model clauses A, B and C), 2.5.10 (Cases in which a reserving State may unilaterally set the effective date of withdrawal of a reservation), 2.5.11 (Partial withdrawal of a reservation), 2.5.11 bis (Partial withdrawal of reservations held to be impermissible by a body monitoring the implementation of a treaty), 2.5.X (Withdrawal of reservations held to be impermissible by a body monitoring the implementation of a treaty) and 2.5.12 (Effect of a partial withdrawal of a reservation). After considering the report, the Commission referred the proposed draft guidelines, including the related model clauses, to the Drafting Committee with the exception of draft guidelines relating to the withdrawal of a reservation held to be impermissible by a treaty-monitoring body (i.e., 2.5.4, 2.5.11 bis and 2.5.X).

At the same session, the Commission provisionally adopted the following eleven draft guidelines as well as the commentaries thereto: 2.1.1 (Written form), 2.1.2 (Form of formal confirmation), 2.1.3 (Formulation of a reservation at the international level), 2.1.4 [2.1.3 bis, 2.1.4] [32]  (Absence of consequences at the international level of the violation of internal rules regarding the formulation of reservations), 2.1.5 (Communication of reservations) 2.1.6 [2.1.6, 2.1.8] (Procedure for communication of reservations), 2.1.7 (Functions of depositaries), 2.1.8 [2.1.7 bis] (Procedure in case of manifestly [impermissible] reservations), [33]  2.4.1 (Formulation of interpretative declarations), [2.4.2 [2.4.1 bis] (Formulation of an interpretative declaration at the internal level)], [2.4.7 [2.4.2, 2.4.9] (Formulation and communication of conditional interpretative declarations)]. [34]

At its fifty-fifth session, in 2003, the Commission had before it the Special Rapporteur’s eighth report [35]  relating to withdrawal and modification of reservations and interpretative declarations as well as to the formulation of objections to reservations and interpretative declarations. The Special Rapporteur proposed the following draft guidelines: 2.3.5 (Enlargement of the scope of a reservation), 2.4.9 (Modification of interpretative declarations), 2.4.10 (Modification of a conditional interpretative declaration), 2.5.12 (Withdrawal of an interpretative declaration), 2.5.13 (Withdrawal of a conditional interpretative declaration), 2.6.1. (Definition of objections to reservations), 2.6.1 bis (Objection to late formulation of a reservation) and 2.6.1 ter (Object of objections). In addition, he proposed three revised draft guidelines: 2.4.3 (Time at which an interpretative declaration may be formulated or modified), 2.4.6 (Late formulation or modification of an interpretative declaration), and 2.4.8 (Late formulation or modification of a conditional interpretative declaration), [36]  so as to accommodate modification alongside the formulation of interpretative declarations.

After considering the report, the Commission decided to refer to the Drafting Committee the following proposed draft guidelines: 2.3.5 (Enlargement of the scope of a reservation), 2.4.9 (Modification of interpretative declarations), 2.4.10 (Modification of a conditional interpretative declaration), 2.5.12 (Withdrawal of an interpretative declaration) and 2.5.13 (Withdrawal of a conditional interpretative declaration). [37]

At the same session, the Commission provisionally adopted the following eleven draft guidelines (with three model clauses) as well as the commentaries thereto: 2.5.1 (Withdrawal of reservations), 2.5.2 (Form of withdrawal), 2.5.3 (Periodic review of the usefulness of reservations), 2.5.4 [2.5.5] (Formulation of the withdrawal of a reservation at the international level), 2.5.5 [2.5.5 bis, 2.5.5 ter] (Absence of consequences at the international level of the violations of internal rules regarding the withdrawal of reservations), 2.5.6 (Communication of withdrawal of a reservation), 2.5.7 [2.5.7, 2.5.8] (Effect of withdrawal of a reservation), 2.5.8 [2.5.9] (Effective date of withdrawal of a reservation, including model clauses A, B and C), 2.5.9 [2.5.10] (Cases in which a reserving State or international organization may unilaterally set the effective date of withdrawal of a reservation), 2.5.10 [2.5.11] (Partial withdrawal of a reservation) and 2.5.11 [2.5.12] (Effect of a partial withdrawal of a reservation). [38]

At its fifty-sixth session, in 2004, the Commission had before it the ninth report of the Special Rapporteur. [39] After considering the report, it decided to refer draft guidelines 2.6.1 “Definition of objections to reservations” and 2.6.2 “Objection to the late formulation of widening of the scope of a reservation” to the Drafting Committee.

On the basis of the report of the Drafting Committee, the Commission further considered and provisionally adopted draft guidelines 2.3.5 (“Widening of the scope of a reservation”), 2.4.9 (“Modification of an interpretative declaration”), 2.4.10 (“Limitation and widening of the scope of a conditional interpretative declaration”), 2.5.12 (“Withdrawal of an interpretative declaration”), and 2.5.13 (“Withdrawal of a conditional interpretative declaration”), with commentaries thereto. [40]

At its fifty-seventh session, in 2005, the Commission considered part of the tenth report of the Special Rapporteur. [41] On the basis of that report, the Commission decided to refer draft guidelines 3.1 (Freedom to formulate reservations), 3.1.1 (Reservations expressly prohibited by the treaty), 3.1.2 (Definition of specified reservations), 3.1.3 (Reservations implicitly permitted by the treaty) and 3.1.4 (Non-specified reservations authorized by the treaty) to the Drafting Committee. The Commission also decided to send draft guidelines 1.6 and 2.1.8, which had already been provisionally adopted, to the Drafting Committee with a view to their revision in the light of the terms selected. The Commission also decided to continue its consideration of the tenth report during its fifty-eighth session (2006).

The Commission further considered and provisionally adopted draft guidelines 2.6.1 (Definition of objections to treaties) and 2.6.2 (Definition of objections to the late formulation or widening of the scope of a reservation) with commentaries thereto. [42]

The work of the Commission on the topic as described above has been proceeding in accordance with the successive resolutions adopted by the General Assembly under the item relating to the report of the International Law Commission. [43]

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