CYIL vol. 8 (2017)

CYIL 8 ȍ2017Ȏ FAILURE TO REACT AS EVIDENCE OF OPINIO IURIS a derogation from an established custom in every case then scores of special relationships would emerge between different states depending upon acquiescence and protest”. 19 It seems that, having regard to the practice of states, it is possible that in these cases, the states rely on the already existing, clearly established customary norm and, therefore, regard themselves absolved from the need to react to each and every instance of practice of other states which deviates from such a norm; in addition, they may rely on their practice and explicit expressions of their opinio iuris which otherwise, in other contexts, consistently and unequivocally adhere to the already established customary norm. VI. In this regard, perhaps, the practice of states may be compared with the reactions of states in the area of reservations to treaties. Although the reservations, by their definition, purport to affect rights of other parties to a treaty, it woud be, in the words of A. Aust, “wrong to think that every foreign ministry agonises over every reservation notified to it; even in the best-managed of them, reservations are not always given the attention they deserve. There are many other matters to attend to, and reservations may not be seen as priority. If one studies any list of reservations it is surprising how few states object, even though a clearly objectionable reservation has been made”. 20 He adds that “[t]he Convention [on the Law of Treaties]… puts the onus on the objecting state both to express its objection and, if it does not want the treaty to enter into force between it and the reserving state, to say so explicitly. In putting this responsibility on the objecting state, the Conference [which adopted the Convention on the Law of Treaties] did not take sufficiently into account the actual practice of states”. 21 In addition, in case of reservations which are incompatible with the object and purpose of the treaty under Article 19 (c) of the Vienna Convention on the Law of Treaties, other parties to a treaty, as a matter of principle, do not need to raise objections against such reservations since these reservations are prohibited on the basis of the objective incompatibility test provided for in the Vienna Convention, 22 and, therefore, cannot exclude or modify the legal regime between them and the reserving state in any way (although raising objections in such cases is very advisable so that the objective incompatibility of such reservations with the object and purpose of a treaty may be more clearly established). It may be that, similarly, in case of an existing, established norm of customary international law, states do not feel the need to react to each and every single conduct of other states which deviates from the customary norm since they rely on some kind of objective test of incompatiblity of the conduct (practice) in question with such a customary norm. VII. Possible risks contained in the current approach of the Commision to the concept of the “failure to react” may be further illustrated by the Commission’s approach to the particular (regional) customary international law. According to the Commission’s commentary to the draft conclusion 16, 23 “although particular customary international law is mostly regional, sub-regional or local, there is no reason in principle why a rule of particular customary Shaw , M. N., op. cit. sub 14, p. 64. 20 AUST, A., Modern Treaty Law and Practice , 3rd edition (Cambridge University Press, 2013), p. 128. 21 AUST, A., ibid ., p. 128. 22 AUST, A., ibid. , pp. 129-131. 23 Conclusion 16 (Particular customary international law): 1. A rule of particular customary international law, whether regional, local or other, is a rule of customary international law that applies only among a limited number of States. 2. To determine the existence and content of a rule of particular customary international law, it is necessary to ascertain whether there is a general practice among the States concerned that is accepted by them as law ( opinio juris ); ILC, Report on the work of the sixty-eighth session, doc. A/71/10, pp. 114-115. 19

113