6 the rules of interpretation set forth in international law (such as those formulated in Articles 31-33 of the two Vienna Conventions on the Law of Treaties, of 1969 and 1986), comprise not only the substantive norms (on the protected rights) but also the clauses that regulate the mechanisms of international protection. 14. The Inter-American Court of Human Rights has the duty to preserve the integrity of the regional conventional system of protection of human rights as a whole. It would be inadmissible to subordinate the operation of the conventional mechanism of protection to restrictions not expressly authorized by the American Convention, interposed by the States Parties in their instruments of acceptance of the optional clause of compulsory jurisdiction of the Inter-American Court (Article 62 of the American Convention). This would not only immediately affect the efficacy of the operation of the conventional mechanism of protection, but, furthermore, it would fatally impede its possibilities of future development. 15. By virtue of the principle ut res magis valeat quam pereat, which corresponds to the so-called effet utile (sometimes called principle of effectiveness), widely supported by case-law, the States Parties to human rights treaties ought to secure to the conventional provisions the proper effects at the level of their respective domestic legal orders. Such principle applies not only in relation to the substantive norms of human rights treaties (that is, those which provide for the protected rights), but also in relation to the procedural norms, in particular those relating to the right of individual petition and to the acceptance of the contentious jurisdiction of the international judicial organ of protection 22. Such conventional norms, essential to the efficacy of the system of international protection, ought to be interpreted and applied in such a way as to render their safeguards truly practical and effective, bearing in mind the special character of the human rights treaties and their collective implementation. 16. The European Court of Human Rights had the occasion to pronounce in this respect. Thus, in its Judgment on Preliminary Objections (of 23.03.1995) in the case of Loizidou versus Turkey, it warned that, in the light of the letter and the spirit of the European Convention the possibility cannot be inferred of restrictions to the optional clause relating to the recognition of the contentious jurisdiction of the European Court 23, by analogy with the permissive State practice under Article 36 of the Statute of the ICJ; under the European Convention, a practice of the States Parties was formed precisely a contrario sensu, accepting such clause without restrictions 24. 22 . Cf., to this effect, the decision of the old European Commission of Human Rights (EComHR) in the case Chrysostomos et alii versus Turkey (1991), in EComHR, Decisions and Reports, vol. 68, Strasbourg, C.E., [1991], pp. 216-253; and cf., earlier on, the obiter dicta of the Commission, to the same effect, in its decisions i the Belgian Linguistic Cases (1966-1967) and in the cases Kjeldsen, Busk Madsen and Pedersen versus Denmark (1976). 23 . Article 46 of the European Convention, prior to the entry into force, on 01.11.1998, of Protocol n. 11 to the European Convention. 24 . To that it added, moreover, the fundamentally distinct context in which international tribunals operate, the ICJ being "a free-standing international tribunal which has no links to a standard-setting treaty such as the Convention"; cf. European Court of Human Rights (ECtHR), Case of Loizidou versus Turkey (Preliminary Objections), Strasbourg, C.E., Judgment of 23.03.1995, p. 25, par. 82, and cf. p. 22, par. 68. On the prevalence of the conventional obligations of the States Parties, cf. also the Court's obiter dicta in its previous decision anterior, in the case Belilos versus Switzerland (1988). - The Hague Court, in its turn, in its Judgment of 04.12.1998 in the Fisheries Jurisdiction case (Spain versus Canada), yielded to the voluntarist subjectivism of the contending States (cf. ICJ Reports (1998) pp. 438-468), the antithesis of the very notion of international compulsory jurisdiction, - provoking Dissenting Opinions of five of its Judges, to whom the ICJ put at risk the future itself of the mechanism of the optional clause under Article 36(2) of its Statute, paving