The Legality of Forcible Intervention by Invitation under International Law

As “the threat or use of force” is generally prohibited under Article 2(4) of the United Nations Charter, the principle prohibiting the use of force has been firmly established as a general principle of international law. In addition, as an exception to the principle prohibiting the use of force, it is generally recognized that the exercise of the right of self-defence against prior armed attack or the use of force under the approval of the United Nations Security Council is exceptionally permitted. Nevertheless, in order to justify the use of force in the international community, States have used various international legal justifications, including anticipatory or preemptive self-defence, humanitarian intervention, protection of overseas nationals, protection of democracy, and self-determination. The so-called “intervention by invitation” is one of the main justifications that States claim to intervene in foreign civil war. However, if consent is granted by the requesting state, there would be no “use of force” prohibited from the beginning, so the intervention cannot be regarded exception to Article 2(4) of the United Nations Charter. Despite the relevant principles of international law related to foreign forcible intervention, especially the principle prohibiting the use of force, non-intervention, and self-determination, intervention by invitation is clearly permitted under international law. Nevertheless, if a State intervenes in another state's civil war and uses “intervention by invitation” as a legal justification, the question arises as to who has the authority to request forcible intervention, that is, what is the criterion for judging a legitimate government under international law. For this reason, most of the controversies related to “intervention by request” arise due to the question of who can give valid consent. In this paper, we first theoretically review the legality of intervention by invitation under international law, and then comprehensively review the controversy raised when intervention by invitation is invoked, especially in the context of civil war.