CYIL vol. 9 (2018)

CYIL 9 ȍ2018Ȏ CUSTOMARY INTERNATIONAL LAW, INTERPRETATION OF TREATIES … forms, including binding treaties, non-binding instruments, but also internal legislative, executive and judicial acts, and other conduct. 32 Paragraph 3 provides that in identifying subsequent practice under article 32, the interpreter is required to determine whether the conduct by one or more parties is in the application of the treaty. 33 Conclusion 7 deals with the possible effects of subsequent agreements and subsequent practice. It indicates that subsequent agreements and subsequent practice, in their interaction with other means of interpretation, may contribute to the clarification of the meaning of a treaty. This may result in narrowing, widening, or otherwise determining of possible interpretations. Paragraph 3 addresses the possible relation between the interpretation and modification of a treaty, providing a presumption that the parties to a treaty, by an agreement or by practice in the application of the treaty, intend to interpret the treaty, not to amend or to modify it. 34 Conclusion 8 addresses the issue of evolving or evolutive interpretation. It provides that “subsequent agreements and subsequent practice under articles 31 and 32 may assist in determining whether or not the presumed intention of the parties upon the conclusion of the treaty was to give a term used a meaning which is capable of evolving over time”. 35 Conclusion 9 identifies some criteria helpful in determining the interpretative weight to be accorded to a specific subsequent agreement or subsequent practice. It depends on its clarity, specificity, and other factors. In addition, the weight of subsequent practice under article 31, para. 3(b), also depends on whether and how it is repeated. 36 Conclusion 10 refers to an agreement of the parties. An agreement under article 31, paragraph 3 (a) and (b), requires “a common understanding regarding the interpretation of a treaty which the parties are aware of and accept”. According to this conclusion, such an agreement may, but need not, be legally binding. By contrast, paragraph 2 concerns only an agreement under article 31, para. 3(b), i.e. resulting from subsequent practice, where the number of parties that must actively engage may vary. The second sentence clarifies that silence on the part of one or more parties may constitute acceptance of the subsequent practice when the circumstances call for some reaction. 37 Lastly, Part Four deals with the three specific aspects of subsequent agreements and subsequent practice. Conclusion 11 first defines a “Conference of States Parties”. Then it provides that depending on the circumstances, decisions of a Conference of States Parties may embody a subsequent agreement under article 31, para. 3 (a), or give rise to subsequent practice under article 31, para. (b), or to subsequent practice under article 32. 38 Next, conclusion 12 addresses constituent instruments of international organizations. It confirms that articles 31 and 32 also apply to a treaty which is the constituent instrument of an international organization. It implies (para. 2) that subsequent agreements and subsequent practice may arise from, or be expressed in, the practice of an international organization in the application of its constituent instrument. In addition (para. 3), practice of an organization itself in the

32 Ibid., p. 37. 33 Ibid., p. 37. 34 Ibid., p. 38. 35 Ibid., p. 51. 36 Ibid., p. 58. 37 Ibid., p. 63. 38 Ibid., p. 70.

371