CYIL vol. 11 (2020)

SILVANO DENEGA SOUZA CYIL 11 (2020) translates into the substantive element (an external aspect, the legislative intent, retrieved from state’s subjective political matrix – which can be variable over time). 44 With regards to opinio juris , briefly arguing, it is the common understanding over certain aspect, the uniform legal assessment of a definite conduct. In The Politics of International Law , Koskenniemi observes that, as for the International Court of Justice, there is no independently applicable criteria to ascertain the presence of opinio juris . This means that the Court has been inferring the presence or absence of this element while purely assessing the extent and intensity of the material conduct. 45 Therefore we learn from Koskenniemi’s teaching: material conduct is primarily addressed. Following this rationale, the International Court of Justice has assumed the existence of a formed opinio juris solely from the evidence of a general practice, or even from consensus in the writings of publicists. There are few cases in which the Court acts strictly, requiring more ‘positive’ 46 evidence. As for general practice, it is worth remembering, there is no need for absolute state practice related to a law, it suffices to be recurrent. Apparently, the verification of customary international rule is circular: the conduct (general practice) tends to be an evidence of state intent ( opinio juris ). Yet, it is with foundation in opinio juris itself that one conduces the assessment of which practice proves relevance to acquire custom status. 47 In general, a law acquires international customary status when a certain principle is ‘invoked by a majority of states, comprising both developed and developing countries, by a regional group of states, (…) or even by the international community, including international civil society.’ 48 This classification, according to Pierre-Marie Dupuy, would depend on a few other factors in order to reach custom status, such as how it was referred to in the treaty or soft law instrument, entry into force , judicial decisions and other forms of state practice . From this context, Dupuy also stresses: ‘the process of the formation of customary international law, and that of its consolidation as a rule of positive international law are two sides of the same coin.’ 49 The formation of customary international law goes necessarily through consent of the sovereign states conforming the international community. Given the nature of custom, as we have seen, in absolutely no way a sovereign state can be compelled to accept certain rules as customary. In this sense […] states do not become subject to international legal obligations unless they have first given their consent. This consent, however, may come in the form of general consent to the process of customary international law, and not as specific consent to individual rules. […] By accepting some rules of customary international law states

44 Ibid 410. 45 KOSKENNIEMI, Martti, The Politics of International Law (Hart 2011) 56. 46 Brownlie (n 38) 9. 47 Koskenniemi (n 42) 57.

48 DUPUY, Pierre-Marie, ‘Formation of Customary International Law and General Principles’, in BODANSKY, Daniel, BRUNNÉE, Jutta and HEY, Ellen (eds.) The Oxford Handbook of International Environmental Law (Oxford University Press 2010) 451. 49 Ibid 451.

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