EN
A basic principle of international law is the prohibition of the use of armed force, which is regulated in Article 2 of the UN Charter. Charter provides for two exceptions to this rule, and one of them is the right to self-defence. This right for it legality must meet certain conditions in both the United Nations Charter and by customary law. The right to self defence is a right derived from common law and the Charter makes its confirmation and concretization. A prerequisite for taking action in self-defence is an instance of an armed attack. Further conditions to be met in action of self-defence are the conditions of proportionality and necessity, which are not mentioned by the UN Charter but have their confirmation in the common law as well as have been confirmed by the International Court of Justice.