This article is referenced to the thirtieth anniversary of the ICJ’s Nicaragua judgement on the merits of 1986. It acknowledges the significance of this much-debated judgement for the modern international law on the use of force (jus ad bellum). However the text focuses on one aspect of the judgment only, i.e. the definition of the notion of “armed attack” as the most grave form of the use of force. The impact of the judgement in this respect is critically analysed. It is argued that the introduction to the UN Charter text of undefined notions of the use of force, aggression, and armed attack may be labelled as the “original sin” of contemporary jus ad bellum, as it results in conceptual obscurity. It is also claimed that the ICJ reaffirmed this original sin in its Nicaragua judgment because it explicitly argued for the notion of “armed attack” as the most grave form of the use of armed force and, in consequence, distinguished it from the other, lesser forms of the use of force, while failing to introduce any sort of clarity in the conceptual ambiguity of jus ad bellum. The article also offers some remarks de lege ferenda and suggests abandoning the gravity criterion, which would require abandoning the well-established judicial and doctrinal interpretation approaches to jus ad bellum.

In light of contemporary circumstances, on the 30th anniversary of the Nicaragua judgment it is worth revisiting and considering again certain legal problems decided by – and raised by – the ICJ judgment. This article addresses the importance of the judgment in terms of international legal regulations on the use of force. First and foremost, the article examines the concept of armed attack based on the “gravity” criterion elaborated by the Court and the exercise of the right of self-defence. Moreover, the relationship between customary international law and treaty law, as well as forcible counter-measures and military actions against non-State actors are also discussed in the article. It is argued that the “gravity” criterion used by the ICJ seems controversial and, consequently, may limit the right of self-defence. On the other hand, however, the judgment established a strong barrier to the realization of individual political interests by militarily powerful States. This is the Nicaragua judgment’s long-lasting legacy. In this sense the judgment has stood the test of time.

Ukraine, upon giving up the nuclear arsenal left on its territory by the USSR, entered in 1994 into a Memorandum on Security Assurances with the United Kingdom, United States and Russian Federation (Budapest Memorandum). Since the crisis began between the Russian Federation and Ukraine in February 2014, a number of States have invoked the Budapest Memorandum. Unclear, however, is whether this instrument constituted legal obligations among its Parties or, instead, is a political declaration having no legal effect. The distinction between political instruments and legal instruments is a recurring question in inter-State relations and claims practice. The present article considers the Budapest Memorandum in light of the question of general legal interest – namely, how do we distinguish between the legal and the political instrument?

The aim of this article is to assess the military operation started on 24 February 2022 by Russia against Ukraine in light of the law on use of force, having in mind all the justifications officially expressed by Russian authorities and in light of international humanitarian law. The author claims that there is no justification for the Russian military action and thus it must be qualified as aggression. This, due to the serious violation of the peremptory norm, implies obligations on the part of states and international organizations (i.e. the international community). In addition, the current conduct of hostilities clearly shows that it is mainly Russian forces which neglect international humanitarian law principles, which might amount to war crimes.

Following the so-called “special military operation”, which was in fact an open aggression against Ukraine, Russia was expelled from the Council of Europe. This step has significant legal consequences, including for the jurisdiction of the European Court of Human Rights. Meanwhile, many individual applications were filed with the Court, and Ukraine brought an inter-State complaint against Russia. Ukraine has also triggered the International Court of Justice. The Court has already ordered provisional measures. The ICC Prosecutor has launched an investigation into the most serious international crimes, war crimes, crimes against humanity, and genocide in Ukraine and delivered arrest warrants against the Russian President and his Commissioner for Children’s Rights. There is a serious discussion going on concerning the establishment of a special tribunal for the crime of aggression. This text deals with some aspects of the Russian “special military operation” cases before international courts. It attempts to identify what role the international courts may play in the new phase of the conflict in Ukraine and the extent and effect of their intervention, given the jurisdictional limitations and the inability to enforce judgments.