Abstract: The legitimate self-defence is expressly provided in Article 51 of the Charter of the United Nations, as a derogation from the basic principle that prohibits the use of armed force. As the International Court of Justice stated, the right to legitimate self-defence is part of customary international law, but neither the international jurisprudence nor the legal instruments subsequent to the adoption of the Charter expressly establish several forms of legitimate self-defence thus leaving room for controversy and debate on the conditions which the victim State must comply with in order for the self-defence action to be considered justified and legitimate. The purpose of this paper is to analyze the normative framework on legitimate self-defence, its legality requirements, the notion of ”preventive self-defence” and to address the possible implications of terrorist attacks on changes of the scope of legitimate self-defence in International Law.

Keywords: legality, self-defence, preventive, terrorist attacks