41. Legal consequences of a serious breach of a peremptory norm: the international rights and duties of states in relation to a breach of the prohibition of aggression
In August 2022, the Minister of Foreign Affairs requested advice on the legal consequences of a serious breach of a peremptory norm of international law (jus cogens). This request for advice was prompted by the Russian Federation’s invasion of Ukraine, which is referred to in the request as ‘a serious breach of the prohibition on the use of force and of the territorial integrity and political independence of Ukraine.’
This advisory report concerns the international rights and obligations of states (including third states) in the event of serious breaches of peremptory norms of general international law, in particular the prohibition of aggression.
Part I deals with three specific obligations arising from Article 41 of the Articles on State Responsibility (ARSIWA), namely (1) the obligation to cooperate in order to bring the breach to an end, (2) the obligation not to recognise as lawful a situation created by the breach, and (3) the obligation not to render aid or assistance in maintaining that situation.
Part II examines the subject of sanctions and, more specifically, whether third states may take countermeasures in the general interest, i.e. whether third states may take measures which in normal circumstances would themselves also constitute a breach of international law but are justified as a response to a serious breach of a peremptory norm of international law, in particular the prohibition of aggression.