The interference by one state in the internal or external affairs of another state. It could refer to  interference in a state’s freedom to choose its political, economic, social, or cultural path, or to interference in the formulation of its foreign policy. Intervention may take the form of military action, or it may be undertaken through the exertion of economic or political pressures. However, it will be unlawful under international law if such interference is achieved through the use of force, be it in the direct form of military action or in the indirect form of support for subversive or terrorist armed activities within another state.  

If third States and/or international organizations intervene militarily in ongoing non-international armed conflicts in support of the non-State armed group party to the conflict, this internationalizes the conflict.

See Classification of conflicts; Internationalized internal armed conflicts;

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 LEGAL SOURCE

 CASES

 BIBLIOGRAPHIC RESOURCES

CHESTERMAN Simon, Just War or Just Peace: Humanitarian Intervention and International Law, Oxford, OUP, 2001, 295 pp.   CORTEN Olivier & KLEIN Pierre, “Action humanitaire et chapitre VII: la redéfinition du mandat et des moyens d’action des forces des Nations Unies”, in AFDI, 1993, pp. 105-130.   GIROD Christophe & GNAEDINGER Angelo, “Politics, Military Operations and Humanitarian Action: An Uneasy Alliance”, Geneva, ICRC, 1998, 29 pp.   MOORE Jonathan (ed.), Hard Choices: Moral Dilemmas in Humanitarian Intervention, New York, Rownan and Littlefield, 1998, 322 pp.   RUFIN Jean-Christophe, Le piège, quand l’aide humanitaire remplace la guerre, Paris, Lattès, 1986, 336 pp.   SAPIR Debarati G., “The Paradox of Humanitarian and Military Intervention in Somalia”, in WEISS Thomas G. (ed.), The United Nations and Civil Wars, London, Lynne Rynner, 1995, pp. 151-172.   TESÓN Fernando, Humanitarian Intervention: An Inquiry into Law and Morality, Dobbs Ferry, Transnational Publishers, 1988.