Chapter 1 • International Human Rights Law and the Role of the Legal Professions: A General Introduction The judge will thus have to assess the existence of one objective element consisting of the general practice, and one subjective element, namely, that there is a belief among States as to the legally binding nature of this practice.17 With regard to the question of practice, it follows from the ruling of the International Court of Justice in the North Sea Continental Shelf cases that, at least with regard to “the formation of a new rule of customary international law on the basis of what was originally a purely conventional rule”, the passage of time can be relatively short, although “an indispensable requirement would be that within the period in question, short though it might be, State practice, including that of States whose interests are specially affected, should have been both extensive and virtually uniform in the sense of the provision invoked; – and should moreover have occurred in such a way as to show a general recognition that a rule of law or legal obligation is involved”.18 In the subsequent case of Nicaragua v. the United States of America, the International Court of Justice appears however to have somewhat softened this rather strict interpretation of the objective element of State practice, whilst at the same time placing a correspondingly greater emphasis on the opinio juris in the creation of custom. In its reasoning, which related to the use of force, the Court held, in particular: “186. It is not to be expected that in the practice of States the application of the rules in question should have been perfect, in the sense that States should have refrained, with complete consistency, from the use of force or from intervention in each other’s internal affairs. The Court does not consider that, for a rule to be established as customary, the corresponding practice must be in absolutely rigorous conformity with the rule. In order to deduce the existence of customary rules, the Court deems it sufficient that the conduct of States should, in general, be consistent with such rules, and that instances of State conduct inconsistent with a given rule should generally have been treated as breaches of that rule, not as indications of the recognition of a new rule. If a State acts in a way prima facie incompatible with a recognized rule, but defends its conduct by appealing to exceptions or justifications contained within the rule itself, then whether or not the State’s conduct is in fact justifiable on that basis, the significance of that attitude is to confirm rather than to weaken the rule”.19 The question now arises as to what legal principles for the protection of the human person might have been considered to form part of customary international law by the International Court of Justice. In its Advisory Opinion of 1951 on Reservations to the Convention on Genocide, the Court importantly held that “the principles underlying the Convention are principles which are recognized ... as binding on States, even without any conventional obligation”.20 Furthermore, it followed from the Preamble to the Convention that it 17 Ibid., loc. cit. 18 Ibid., p. 43, para. 74. 19 Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), Merits, Judgment, ICJ Reports 1986, p. 98, para. 186. 20 Reservations to the Convention on Genocide, Advisory Opinion, ICJ Reports 1951, p. 23. Human Rights in the Administration of Justice: A Manual on Human Rights for Judges, Prosecutors and Lawyers 9