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The use of force in international law
The use of force in international law

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1.1 The post-1945 legal framework

The current legal framework regulating the use of force in international law is enshrined in the UN Charter. The maintenance of international peace and security is the primary purpose of the UN (Article 1(1) UN Charter). This includes:

prevention and removal of threats to the peace, [...] the suppression of acts of aggression or other breaches of the peace, [...] and in conformity with the principles of justice and international law, adjustment or settlement of international disputes or situations which might lead to a breach of the peace.

Therefore, as a general rule of international law, the use of force is prohibited.

Box 1 The illegality of the use of force

Although states have resorted to the use of force in international relations on multiple occasions, there have been only two cases in which the International Court of Justice (ICJ) has found that there had been a violation of the prohibition of the use of force:

  • Military and Paramilitary Activities in and against Nicaragua (Nicaragua v The United States of America) ICJ Rep 1986
  • Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda) ICJ Rep 2005.

The UN Charter further provides that:

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.

(Article 2(4) UN Charter)

As you may have noticed from the wording of Article 2(4), prohibited acts include both the threat of force and the use of it.

It is important to remember that the prohibition on the use of force is not absolute. As the wording of Article 2(4) suggests, the force is permissible in circumstances consistent with the purposes of the UN. Chapter VII of the UN Charter (‘Action with Respect to Threats to the Peace, Breaches of the Peace, and Acts of Aggression’), outlines when a state can resort to the use of military force against other states. Force may be used against another state when:

  • such an act is authorised by the UN Security Council as part of collective security mechanism
  • a state is acting in self-defence.

You will now consider these situations in more detail.