The Conference on the Law of Treaties held at Vienna in 1968 and 1969, like the other important United Nations conferences on the codification of international law (Geneva Conferences on the Law of the Sea of 1958 and 1960, Vienna Conference on Diplomatic Intercourse and Immunities of 1961 and Vienna Conference on Consular Relations of 1963), formulated and adopted a Convention on the basis of a draft which was the collective work of the International Law Commission (ILC) of the United Nations, carried out under the guidance of a Special Rapporteur.We have thus been witnessing since 1958 the interesting process of the reduction into treaty law of a substantial part of the customary international law of peace; if this period is compared with the centuries that went before, the transformation of unwritten rules into written law which has thus taken place appears remarkably fast. This codification of public international law has of course served to clarify pre-existing rules but it has at the same time made it possible to bring these rules up to date so as to meet better the new requirements of the community of States—the society which is governed by that law and which has undergone significant changes in the last few decades.