The international legal content of the concept of sustainable development, so common in international treaties and sometimes expressed in different terms, undoubtedly requires clarification today, as does its place in the system of international law.
Firstly, it is interesting to answer the question of how ideas of sustainable development have resulted in their crystallization as a concept of international law. Secondly, using treaty sources of the international law of the sea, where this notion is particularly common, it is meaningful to identify the intentions of states parties to such treaties to consider sustainable development clauses as legal obligations. Thirdly, it is important to determine whether these clauses now constitute a principle of the international law of the sea or whether they retain the status of separate treaty obligations that are not interrelated.
The article is based on an analysis primarily of the norms of the international law of the sea, in which the term “sustainable development” is applied, with reference to the scientific and legal literature and judicial decisions relevant to the topic. The research involves methods of legal construction, legal modelling, analysis and synthesis, systematic, structural-functional, formal-logical, formal-legal, historical and chronological methods.
The analysis of international treaties and other international legal instruments relating to this issue has shown that the long-standing ideas of “sustainable development” are now normatively well-established; that the provisions of international treaties on sustainable development have already developed as an inter-branch (cross-cutting) principle of international law at the intersection, primarily, of the international law of the sea and international environmental law; and that in practice states undertake explicit obligations and exercise relevant rights in the framework of upholding this crosscutting principle.
The authors’ vision of the content of this principle is offered and its various manifestations in the international law of the sea are shown. The study critically evaluates the prevailing view in the Western international legal literature that the idea of sustainable development was first suggested by the 1987 Report “Our Common Future” (the Brundtland Report). It is shown that the idea predates this report, and that the initial mechanisms for sustainable development had already been reflected in existing international treaties by 1987. The suggestion is made that the international legal concept of sustainable development has several cumulative components that together define its content. Among these there are elements that are part of this concept primarily because they are means of achieving sustainable development goals, having a much narrower scope if interpreted in isolation. The international legal principle of sustainable development seeks to resolve the tensions primarily between the right of states to development and their duty to protect the environment, serving as a nexus that ensures that neither the one nor the other is neglected. Its social dimension is undoubtedly significant, although it has been interpreted very differently in the international legal literature.
In the context of contemporary international law, it would be wise to assert an interbranch (cross-cutting) nature of the sustainable development principle: its legal content extends beyond the scope of specific branches of international law, including international law of the sea, international environmental and economic law. However, most international treaties of a universal and especially regional character that contain some form of sustainable development clauses currently refer to sources of the international law of the sea, which may certainly change in the future.

At various times, the sustainable use of living marine resources in the high seas outside exclusive economic zones, as well as in areas under the jurisdiction of Arctic coastal states, has been severely damaged by illegal, unregulated and unreported fishing. As the climate warms, the threat of unregulated fishing has also emerged on the high seas in the central Arctic Ocean. The Agreement to Prevent Unregulated High Seas Fisheries in the Central Arctic Ocean was signed in Ilullissat (Greenland, Denmark) on October 3, 2018 following multi-round negotiations in the so-called “five plus five” format – representatives of five Arctic states plus representatives of four non-Arctic states and the European Union. This new international legal document reflects national interests in the optimal use of living marine resources of the Arctic states, the Arctic indigenous peoples and residents, as well as interested states.
The present article shows the evolution of international legal instruments to prevent illegal, unregulated and unreported fishing in the high seas. Particular attention is paid to the study of normative and doctrinal materials revealing the treaty practice of states in the Arctic enclaves. A legal interpretation of the provisions of the 2018 Agreement is also given. In the study, the authors used historical, comparative-legal and other general scientific and special legal methods.
From an international perspective, the 2018 Agreement is an innovative legal document that reflects the interests of Arctic and non-Arctic states alike. Despite concerns about the participation of the latter (China, in particular) on the part of Western countries, the Agreement was nevertheless signed and ratified before possible commercial fishing on the high seas in the Central Arctic Ocean starts. This would prevent illegal, unregulated and unreported fishing in advance and thus prevent the depletion of living marine resources in this part of the Arctic Ocean, unlike what happened in other enclaves of the high seas in the Northern Hemisphere.
The entry into force of the 2018 Agreement marked the beginning of cooperation among interested states in the prevention of unregulated high seas fishing in the Central Arctic Ocean. In addition to the general purpose of the Agreement, scientific cooperation between the Parties will contribute to a better understanding of the leastexplored area of the high seas. It is likely that environmental cooperation in the Central Arctic Ocean will expand considerably in the future.