Use of Force under International Law


  1. Highly controversial area of international law. Also, one of the most important areas.
  2. Present international order and international law is principally based on prohibition of the use of force (article 2 (4) of the UN Charter).
  3. Yet, wars have not been prevented. Gray estimates that more than 100 major (international) conflicts have occurred since 1945.
  4. Also the development of the concept such as “self-determination wars”, “humanitarian intervention”, “intervention by invitation” etc.
  5. The UN Charter
  6. The UN charter, in response to the horror of the second world war, prohibited use of force and centralized the power to the security council.
  7. The drafters had hoped to create a standing UN army, however this never materialized. Instead, the big powers who enjoyed veto in the security council dominated the scene. As such, veto obstructed maintenance of peace in many occasions when armed conflict broke.
  • Peace keeping forces was developed but did not exercise effective power in preventing conflicts.
  1. Definition of Agression, GA R 3314, Declaration on Friendly Relations GAR 2625, Declaration on the Non-use of force GAR 44/22 tried to define the concept. However, they all were ambiguous.
  2. ICJ decisions: the Nicaragua Case, the Legality of the Threat or use of Nuclear Weapons Advisory Opinion, the Oil Platforms Case, the Case Concerning Armed Activities on the Territory of the Congo (DRC v. Uganda).
  3. The scheme of article 2 (4)
  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.
  5. Additionally, according to article 2 (6) of the Charter, “the Organization shall ensure that states which are not Members of the United Nations act in accordance with these Principles so far as may be necessary for the maintenance of international peace and security.”
  • Article 2 (4) is believed to have reached the status of customary international law even jus cogens (see Nicaragua Case)
  1. Threat or Use of Force
  2. Developed countries argue only armed force falls under article 2(4), while developing countries argue for wider interpretation of article 2(4) covering armed force as well as other forms of economic or political force.
  3. The ICJ has defined “use of force” broadly. In Nicaragua Case, it held that not only the laying of mines in Nicaraguan waters and attacks on Nicaraguan ports and oil installations by US forces but also support for contras engaged in forcible struggle against the government could constitute the ‘use of force’. The arming and training of the contras involved the use of force against Nicaragua, but the mere supply of funds did not in itself amount to a use of force.
  • Threat of use of force has not yet been defined. However, the ICJ has found that possession of nuclear weapons as not unlawful threat of force.
  1. Exceptions: Self Defense, Humanitarian Intervention(?), and Chapter VII use of force
  2. Self-Defense: article 51 of the Charter
  3. 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, until the Security Council has taken measures necessary to maintain international peace and security. Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.
  • Debate: whether article 51 is exhaustive or there is a room to find additional conditions, such as, anticipatory self defense or protection of nationals abroad.
  1. Condition precedent for self-defense: necessity and proportionality (customary international law)
  2. What is an armed attack?: The UN GAR Definition of Agression: Aggression is the use of armed force by a State against the sovereignty, territorial integrity or political independence of another State, or in any other manner inconsistent with the Charter of the United Nations, as set out in this Definition.
  3. Nicaragua Case: an armed attack includes “the sending by or on behalf of a state of armed bands, groups, irregulars or mercenaries, which carry out acts of armed force against another state of such gravity as to amount to an actual armed attack or its substantial involvement therein.”
  4. Use of force under Chapter VII
  5. Peacekeeping and Peace Enforcing: Certain Expense Case, Cold war.
  6. Humanitarian Intervention:
  7. The United Nations Security Council Resolution 1973 (2011) authorized member states to “take all necessary measures to protect civilians and civilian populated areas under threat of attack” in Libya on 17 March 2011. The Security Council Resolution came in furtherance of SC Resolution 1970 (2011) that imposed sanctions in Libya. The essence of the Resolution 1973, which, also famously, declared No-Fly Zone in Libya, was intervention in Libya for the purpose of humanitarian assistance and protection of the Libyan people.
  8. The UN system is based on the principle of peaceful settlement of disputes and prohibits use of force in international relations.[1] However, the UN Charter has left a room for the use of force under specific and exceptional circumstances provided in the Charter. First, use of force is permitted as a means of self defense according to article 51 of the UN Charter and second, when authorized by the UN Security Council according to Chapter VII of the Charter, to maintain international peace and security.
  9. However, there has been a long debate in international law on the legality of humanitarian intervention as a ground for the use of force. The carnage in Rwanda, where the genocide wiped up a huge portion of the population, conflict in Yugoslavia, humanitarian crisis in Sudan, Zimbabwe, Sri Lanka and so forth have all demonstrated the fact that sometimes the international community, and even individual state, has to take initiative (including, use force) to protect the people from their own rulers. In this context, humanitarian intervention has been increasingly seen as an answer to the protection of life and fundamental rights of the people. However, the legality of the use of force as a ground for humanitarian intervention under international has always been a difficult question.
  10. Be that as it may, there is no doubt that the decision to use force on the humanitarian ground can only be taken by the UN Security Council, given the limitation of scope of article 51 of the Charter. Thus, the actual question regarding the validity of humanitarian intervention should be whether under international law, and the UN Charter, the Security Council is capable of finding the necessity of humanitarian intervention and following a positive assessment, decide to intervene in one of its member states on humanitarian ground.
  11. At this juncture, it is relevant to roughly define the concept:
  12. “The threat or use of force across state borders by a state (or group of states) aimed at preventing or ending widespread and grave violations of the fundamental human rights of individuals other than its own citizens, without the permission of the state within whose territory force is applied.”[2]
  13. According to the abovementioned definition, prevention or end of widespread and grave violations of the fundamental human rights is central to the justification of humanitarian intervention. However, a literal reading of the Chapter VII of the Charter indicates that the Security Council can only intervene to maintain peace and prevent act of aggression. The instances of humanitarian interventions authorized by the UN Security Council, nevertheless, have interpreted grave violations of fundamental human rights as threat to the world peace, thus creating both moral as well as legal grounds for intervention. Indeed, the recent UN Security Council authorized humanitarian intervention in Libya is an example where the Security Council equated the grave violations of fundamental human rights of Libyan protestors by the Guddafi forces as “a threat to international peace and security”[3]. Therefore, by determining violations of fundamental human rights of the people by their own ruler as a threat to international peace, the Security Council could intervene in Libya.
  14. The International Court of Justice (ICJ) in Barcelona Traction Case[4] has held that the obligation of a state to protect fundamental human rights of the people is owed by the state not only to the people, whose rights are at stake, but also to the entire international community. That is, the ICJ found that the obligation to protect fundamental human rights of the people is obligation erga omnes. Therefore, when protection of fundamental human rights is seen from this prism of obligation erga omnes, whereby the obligation is owed to the entire international community, including the UN security Council, the Council is competent to make assessment regarding humanitarian intervention.
  15. Moreover, perhaps the clearest and, by far, the strongest authority for humanitarian intervention, under international law, is the so called UN ‘Outcome Document’ of 2005.[5] The UN General Assembly resolution adopted in 2005 on the outcome of 2005 World Summit identifies every state’s ‘responsibility to protect’ populations of other states from “genocide, war crimes, ethnic cleansing and crimes against humanity”[6]. The resolution further provides that,
  16. “The international community, through the United Nations, also has the responsibility to use appropriate diplomatic, humanitarian and other peaceful means, in accordance with Chapters VI and VIII of the Charter, to help protect populations from genocide, war crimes, ethnic cleansing and crimes against humanity…. to take collective action, in a timely and decisive manner, through the Security Council, in accordance with the Charter, including Chapter VII…”[7]


  1. Hence, the resolution tried to fill a huge gap in international law and also tried to contribute to the interpretation of the Chapter VII of the Carter in favor of humanitarian intervention.
  2. The UN Security Council Resolution 1973, that called upon members to enforce No-Fly-Zone over Libya and allowed use of force on the ground of humanitarian intervention in Libya was based on the above explained notions. Perhaps, the development of international consensus developed in post cold war era and represented by the 2005 Outcome Document reiterated the legitimacy of use of force on the ground of humanitarian intervention in Libya not the opposite. Nevertheless, Libyan example obviously demonstrates the most vivid and profound evidence of the use of force on the ground of humanitarian intervention.


[1] See, The United Nations Charter, Article XXXXXXXXXXX

[2] J. L. Holzgrefe, The humanitarian intervention debate, ( eds. J.L. Holzgrefe and Robert O. Keohane, Humanitarian Intervention: Ethical, Legal, and Political Dilemmas) Cambridge University Press: Cambridge, 2003) 18.

[3] UN SC R 1973 (17 March 2011).

[4] (Belgium v Spain) (Second Phase) ICJ Rep 1970 3 at paragraph 33.


[6] Para 138-139.

[7] Para 139.