The topicality of the research topic is determined by the following: there are many publications devoted to the life and doctrinal views of Igor Ivanovych Lukashuk in the Ukrainian science of international law, but there has been no systematic and thorough study of them until now. In particular, there is not a single monographic study, and the most fundamental works are the articles of his students V. G. Butkevych, O. V. Zadorozhnyi and others. However, even when comprised their studies do not fully cover the subject of this research. At the same time, the publications issued in the Russian Federation are seemingly limited and cannot be considered exhaustive or completely objective except for those devoted to certain aspects of his biography. Existing studies contain significant gaps and do not cover the entire complex of international legal views of Igor Lukashuk. The novelty of the scientific work lies in the fact that for the first time in the Ukrainian science of international law, the author conducted a comprehensive systematic study of the international legal views of I. I. Lukashuk. Their understanding and application are important in Ukraine’s modern international legal relations. For the first time, the periodization of Igor Lukashuk’s scientific activity in the field of international law is proposed, in particular: 1) ‘Kharkiv-Saratov’ (1945-1963); 2) ‘Kyiv’ (1963-1985); 3) ‘Moscow’ (1985-2006). There are also detailed descriptions of each period. The contribution of Igor Lukashuk to the Vienna Convention on the Law of Treaties of 1969 that took place at the United Nations Conference on the Law of Treaties of 1968-1969 was analyzed as well. It allows us to nominally determine the following periods of Dr. Lukashuk’s participation in the Vienna Conference: the first stage – April 4 - April 30, 1968; the second stage – May 2 - May 20, 1968. Igor Lukashuk’s contribution to the Draft articles on the Responsibility of States for Internationally Wrongful Acts (2001) was also researched. The influence of his legal views on the domestic doctrine of international law is comprehensively analyzed, and its two components are distinguished: doctrinal and scientific-methodological. It has been proven that professor Igor Lukashuk was a versatile international lawyer who worked in various areas of international law. He equally thoroughly formulated and defended his positions in multiple fields. Within the present research, the most critical areas of his scientific work were singled out, namely: 1) the law of treaties and its problems; 2) the law of international responsibility of states; 3) problems of the theory of international law, its functioning and regulation; 4) "conjunctural" works devoted to communist ideology and international law; 5) other works of the scientist, dedicated to specific branches and topics of international public law; 6) articles issued in foreign scientific publications. The fundamental character of his international legal heritage in the law of treaties and its relevance for many future generations of theoreticians and practitioners of international law have been substantiated. As one of the developers of the Vienna Convention on the Law of Treaties, Igor Lukashuk considered the international contractual practice as the basis of the modern system of international legal relations and compliance with treaties as one of the main principles of the modern world order. In his scientific heritage, the scientist analyzed the law of international treaties not only through the prism of the practice of states but also of international organizations. Evidence of the topicality of his scientific output is not only his extensive use of references to domestic and foreign researchers but also the practice of the International Court of Justice and the International Law Commission. Justification of the scholar’s Ukrainian identity and integration of his scientific heritage into the national circulation have been substantiated. For our school of international law, Igor Lukashuk is not only one of the most prominent representatives in its history but also one of its founding fathers. Unfortunately, due to the period of living and working in Moscow, he is associated with Russian science, which cannot be tolerated, especially amid ongoing aggression of the Russian Federation and confrontation, in particular at the official legal level. There is a chance for Ukrainian doctrine to lead this process and fully inscribe his name in history precisely as a Ukrainian international lawyer.
