CYIL vol. 14 (2023)

ERNEST PETRIČ CYIL 14 (2023) there were significant differences regarding some fundamental values and legal concepts between the two ideologically opposed blocs, communication based on clear international law ( lex certa ) was extremely important for maintaining dialogue and consequently the peace between the two blocs. Thus, the priority task of the Commission in the 1950s and 1960s, at the height of the Cold War, was the codification of the diplomatic and consular law 11 which until then was often unclear and differently understood and interpreted. The same applies to international treaty law. The issues of international treaties such as the rules of their conclusion, interpretation, effects, change, the end of their validity etc. have to be clearly regulated by international law since States and other subjects of international law regulate and resolve international problems and disputes, even the most controversial ones, by means of international treaties. 12 At the same time, due to technological development and new possibilities of exploiting the riches of the sea, it was necessary to codify the rules regulating relations among States at sea, which until then had also been governed by unwritten customary international law. The Commission prepared drafts of four conventions on basic issues of modern international law of the sea in 1958. 13 Those conventions were the foundations of the later UN Convention on the Law of the Sea, 14 which regulates all essential issues of relations among States on two-thirds of our planet, on the oceans and seas. At the same time, it was the period of decolonisation, when close to 100 new sovereign States joined the international community and the UN. The process of decolonisation brought to the fore in international law the issues of succession (inheritance) of new States in terms of international treaties, property, debts and guarantees, membership in international organizations, citizenship, etc. 15 11 The Commission prepared drafts of the todays fundamental treaties, sources of international diplomatic and consular law, such as the Vienna Convention on Diplomatic Relations (with two additional protocols), which entered into force on 24. 04. 1964 (text see UN Treaty Series, vol. 500); Vienna Convention on Consular Relations (with two additional protocols), which entered into force on 19. 3. 1967 (text see UN Treaty Series, vol. 596); Convention on Special Missions (with an additional protocol), which entered into force on 21. 6. 1985 (text see UN Treaty Series, vol. 1400; with these conventions, the most important parts of diplomatic and consular law are codified, but the Commission also dealt with a number of other issues of this part of international law, such as the effort to codify the status of state representatives at international organizations of universal character (Vienna Convention on the Representation of States in their Relations with International Organizations of a Universal Character), adopted as a draft on 14. 03. 1975, which has not yet entered into force; text see Official Records of the United Nations Conference on the Representation of States in their Relations with International Organizations, vol. II; on the Commission’s effort to codify this matter and some other questions of diplomatic law, see The Work of vol. I, op. cit. in note 1. 12 The draft of the later Vienna Convention on the Law of Treaties is rightly considered one of the greatest achievements of the Commission. It codifies the norms of customary international treaty law, which were created over centuries of state practice; the convention entered into force on 27. 1. 1980 (text see UN Treaty Series, vol. 1155). 13 The draft articles prepared by the Commission for codification were the basis for the drafts of conventions (Convention on the High Seas; Convention on the Continental Shelf; The Convention on the Territorial Sea and the Contiguous Zone) and the Optional Protocol, which were adopted at the UN conference in Geneva in 1958 and also entered into force, and their content was later integrated into the codification efforts of the UN Conference on the Law of the Sea, which between 1973 to 1982 prepared a draft of the now UN Convention on the Law of the Sea (UNCLOS). 14 UN Convention on the Law of the Sea (UNCLOS), which entered into force on 16.11.1999 (text see UN Treaty Series, vol. I833). 15 In connection with the succession issues, the Commission prepared a draft of the articles of the Convention on the Succession of States with regard to international treaties; on this basis, the conference of plenipotentiaries of States adopted the draft of the Vienna Convention on Succession of States in Respect of Treaties, which entered

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