Article 2(3) of the U.N Charter requires all member states “to settle their international disputes by peaceful means in such a manner that international peace and security, and justice are not endangered.” While Article 2(4) specifically refers to the threat or use of force “against the territorial integrity or political independence of any state …”
The purposes of the U.N. are spelt out in Article 1 of the Charter. The purposes include respect for the principle of equal rights and self-determination and respect for human rights. Article 2(4) has been supplemented by the 1970 General Assembly Declaration on Principles of International Law Concerning Friendly Relations and Co-operation among States in accordance with the Charter of the U.N. To put simply, the resolution says, any threat or use of force by state in accordance with the exceptions provided for under the U.N. Charter, is contrary to, and prohibited by contemporary international law.
The use of force only remains legitimate under international law in particularly well-defined circumstances:
1. In self-defence either individual or collective (in accordance with Article 51 of the U.N. Charter);
2. Collective measures taken under the auspices of the U.N; or
3. If authorized by a competent organ of the U.N.
Under customary law, the use of force had to be justified if states are at peace. The use of force by one state against another with which it was not at war was prima facie unlawful. The circumstances which allowed the exercise of the self-defence were articulated in the now famous communication of the U.S. Secretary of State Webster to the British Government following the Caroline incident.
To summarise, the exercise of force in self-defence was justified under customary international law provided that the need for it was:
3. Immediate; and
4. There was no viable alternative action which could be taken.
The extent of force used in self-defence had to be commensurate with the violation it was being utilized to repel. The above criteria still apply today as the Nicaragua Case affirms. Article 51 of the UN Charter acknowledges the right of self-defence as an inherent right of every state. Self-defence is permissible if an armed attack has taken place and Article 51 confines itself to self-defence only in this situation.
It may be considered to be agreed that an armed attack must be understood as including not merely action by regular armed forces across an international border, but also the sending by or on behalf of a State of armed bands, groups, irregulars or mercenaries which carry out armed force against another state of such gravity as to amount to (inter alia) an actual armed attack conducted by regular forces, or its substantial involvement therein.
The ICJ sees, ICJ Report on Nicaragua case, 1986, no reason to deny, that in customary law, the prohibition of armed attacks may apply to the sending by a state of armed bands to the territory of another state, if such an operation, because of its scale and effects, would have been classified as an armed attack rather than as a mere frontier incident had it been carried at by regular armed forces.
But the court does not believe that the concept of armed attack includes not only acts by armed band where such acts occur on a significant scale but also assistance to rebels in the form of the provision of weapons or logistical or other support. Such assistance may be regarded as a threat or use of force, or amount to intervention in the internal or external affairs of other states.
C. Anticipatory Self-Defence or Pre-Emptive Attack
The right of self-defence which Article 51 acknowledges as “inherent” exists under customary international law that is, independently of Article 51. The justification for anticipatory self-defence can be reconciled with the obligation on U.N. Member States to refrain from either “the threat or use of force”. For example in Israel’s strike on the United Arab Republic in June 1967 or U.S. strike on Iraq in 2003.
States which are threatened with the use of force may take appropriate anticipatory measures to repel such a threat, but such measures can only be justified if:
1. A state is the target of hostile activities of another state;
2. The threatened state has exhausted all alternative means of protection;
3. The danger is imminent;
4. The defensive measures are appropriate to the pending danger.
However, whatever rights states enjoy with respect to the use of force; they are at all time required by the UN Charter and customary international law to settle their dispute by peaceful means.
D. Collective Self-Defence
The right of collective self-defence is recognized by Article 51 of the U.N. Charter. Collective self-defence refers, strictly speaking, to collective defence rather than self-defence. Article 51 is the legal basis of collective agreements such as NATO Alliance in which an attack on one member is treated as an attack on all.
Under Article 51 of the North Atlantic Treaty, the contracting Parties: “Agree than an armed attack against one of more of them in Europe or North America shall be considered an attack against them all; and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognize by article 51 of the Charter of the UN, will assist the Party or Parties so attacked, by taking forthwith, individually, and in concert with the other Parties, use of armed force, to restore and maintain the Security of the North Atlantic Area.
All measures adopted by Members States in self-defence must be reported to the Security Council and the use of force individual or collective self-defence may only be employed until the Security Council has taken appropriate measures to maintain international peace and security. The right of collective self-defence was recognized by the International Court of Justice in the Nicaragua case as existing under customary international law but its legitimate exercise depended on:
1. The declaration by the alleged victim that it had been attacked;
2. The request by that state for assistance.
In the same case the court held that intervention by a third world could only be regarded as lawful “when the wrongful act provoking the response was an armed attack. It can thus be argued that the armed response (Operation Desert Storm) to liberate Kuwait was the exercise by the latter of its legal right to collective self-defence.
E. Humanitarian Intervention
The demise of the Cold War witnessed on increase in the number of civil wars. Media images of human suffering in Somalia, Rwarda, Haiti and the former Yugoslavia have ensured that humanitarian crises have been pushed to the forefront of the international agenda.
The doctrine of humanitarian intervention has as a consequence undergone substantial revision in recent years, with the UN accorded a prominent role. Scholarly debate supports the view that humanitarian intervention by the UN is the preferable course of action.
The international community has demonstrated its willingness to use humanitarian concerns as a basis for intervention into what are essentially civil war conflicts. The alleviation of human suffering would appear to be taking precedence over the principle of state sovereignty.
Nevertheless, the international response to humanitarian crises in the 1990s has been inconsistent and considerable criticism has been directed at operation by the UN intervention in any future crisis will require Security Council authorization.