Use of force in international law

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The use of force by states is controlled by both customary international law and by treaty law.^[1] The UN Charter reads in article 2(4):

All members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the purposes of the United Nations.

This principle is now considered to be a part of customary international law, and has the effect of banning the use of armed force except for two situations authorized by the UN Charter.^[2] Firstly, the Security Council, under powers granted in articles 24 and 25, and Chapter VII of the Charter, may authorize collective action to maintain or enforce international peace and security. Secondly, Article 51 also states that: "Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a member of the United Nations."^[3] There are also more controversial claims by some states of a right of humanitarian intervention, reprisals and the protection of nationals abroad.