Until 1945, there were no customary prohibitions on the use of force by nations if the circumstances warranted such action and if preliminary procedures had been exhausted. The Charter of the United Nations introduced a radical concept, that of prohibition of the use of force by member nations, except under specific state of affairs.
The principle of prohibition of the unilateral resort to force by states is enshrined in Article 2(4) of the Charter, which 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.”
In the absence of an organized structure for enforcing international rights, states had no alternative but to resort to the use of their own means which translated to the use of force in the international sphere. Recourse to coercion was only tolerated by international law due to this inescapable reason. The United Nations Charter recognised this defect and created a network of policies to remedy this situation in the form of Chapters VI and VII of the Charter. While Article 2(4) prohibits the threat or use of force by member nations, the abovementioned Chapters establish procedures for the pacific settlement of disputes and empower the Security Council to act on behalf of the international community to neutralize threats to international peace and security or armed aggressions.
Article 2(4) does not stand by itself as an independent provision prohibiting the threat or use of force by member nations against each other, rather it is a part of a complex and detailed mechanism of placatory settlement of disputes. This principle is one of the most important aspects of modern international law and enjoys universal acceptance as a tenet of customary international law.
There is, however, acceptance of the use of force in the Charter and its indispensability to maintain order in the international community. The use of force is a well-known and accepted fact in the international community which was prevalent in recent years where there was concentration on the fight against terrorism, on regulating the sea, on restoring order in certain States, and on upholding human rights in dictatorial regimes. However, the debates around these incidents hardly questioned the usual norm on the prohibition of force. Instead, what is discussed and is repeatedly the subject of controversy, is the scope and the content of a few exceptions to the prohibition. Also, States which defend their use of military force, do so by claiming that one of the given exceptions apply, rather than by negating that there is a rule of international law which necessitates them justifying every single act of military force.
The International Court of Justice, has, on several occasions, maintained that the prohibition of the use of force, apart from being a conventional norm, is also a part of customary international law. The scope of the prohibition of the use of force is fundamentally determined by the idea of force itself, which, in the context of the UN Charter must be taken to mean as referring exclusively to armed or military force. The preamble of the Charter identifies as a goal, to ensure, by the acceptance of principles and the institution of methods, that armed force shall not be used, except in the common interest of all.
Force, therefore, refers exclusively to military force in the context of prohibition under the UN Charter as well as under customary international law. In relation to the use of armed force or military might, the prohibition must be interpreted broadly to encompass every form of armed force which might be used by States. An extensive reading such as this, is the sole way of accommodating the universally acknowledged fundamental character of the prohibition of the use of force and to fulfil purpose of the UN Charter, which is ensuring that armed force is not used as a norm by States against each other. The use of force between States is meant to be proscribed altogether, excluding on the basis of a recognized legal norm which is established to form an exception to the prohibition.
Although the terms of Article 2(4) direct that the use of force is prohibited against the territorial integrity of states and or their political independence. These are, however, not meant to be indispensable requirements for the prohibition to apply, nor to restrict its scope in any other way. Firstly, the two terms ‘territorial integrity’ and ‘political independence’ are qualified by a third term, that of the threat or use of force covered by the provision, which is one ‘in any other manner inconsistent with the purposes of the United Nations’. Since one of those purposes is clearly to prevent unilateral use of armed force, the third term becomes a blanket phrase.
The wide-ranging interpretation of the prohibition of the use of force is of significance especially when it comes to the use of indirect force by one State against another. The principle of the non-use of force not only prohibits the direct use of force, i.e., the invasion of regular troops or cross-border shooting into the territory of another State, but also the contribution of one State in the use of force by another State or by private individuals, against or in the territory of another State. This predominantly includes the participation in aggressive acts perpetrated by unofficial bands, mercenaries or rebels which fall squarely under the prohibition of the use of force. Thus, the Friendly Relations Declaration, which the ICJ held to be declaratory of customary international law in this respect stated with regard to the principle of the non-use of force, the duty of States to refrain ‘from organizing or encouraging the organization of irregular forces or armed bands, including mercenaries, for incursion into the territory of another State’ and ‘from organizing, instigating, assisting or participating in acts of civil strife or terrorist acts in another State or acquiescing in organized activities within its territory directed towards the commission of such acts, when the acts referred to … involve a threat or use of force’ .
The use of force, as prohibited by international law, must be put in relation to another term of international law, that of aggression. The definition of aggression assumed by the UN General Assembly in 1974, took the term to mean ‘the most serious and dangerous form of the illegal use of force’. Armed attack and aggression both describe particularly grave forms of the use of force and are therefore, under the ambit of the prohibition laid down in Art. 2(4) UN Charter.
Art. 2(4) of the UN Charter prohibits the use of force solely in the international relations between States and, therefore, it does not apply to the use of military force within the territory of a State, neither does it prevent insurgents from founding an armed fight against the established government, nor the government from using armed force against them in retaliation. Insurgents are only protected by the prohibition of the use of force when they succeed in establishing a stabilized de facto regime. Aggressive enforcement actions undertaken by a State against private persons within its own territory do not come under the umbrella of the prohibition of the use of force, both, under the UN Charter and customary international law.
The international relations of a State with another are not influenced if one assents to the use of armed force by another in its territory, including territorial waters. Since sovereign States are, in principle, free to dispose of their territory, they also have the right to dispose of their exclusive right to use that territory, thus to allow military operations of other States on their State territory. Provided that that consent is sincere, the prohibition of the use of force does not apply to armed actions of other States’ forces on the territory of a State whose government has consented to those operations. This does, also, include the intervention of other States’ armed forces in a civil war or in the fight against terrorists by invitation or with the consent of the competent government. The recent practices of collective operations against private terrorist groups or pirates seems to confirm this conclusion.
In order to be concerned by the prohibition, the use of armed force by one State must be focused on the territory of another State. In State practice, aggressive attacks against ships and aircrafts of other States of a non-commercial or military character are also regarded as acts of force against that State and fall under the prohibition of the use of force. Art. 3 (d) which lays down the definition of Aggression qualifies the attack ‘on the land, sea or air forces, or marine or air fleets of another State’ as an act of aggression. Forcible attacks against official, as opposed to private aircrafts or ships of other States are sometimes considered to come within the prohibition of the use of force, when they occur in the territory of the attacking State. In situations where a foreign ship or an aircraft is attacked in the territory of a third State, the use of force is not only directed against the flag State, but also against the State whose territory is harmed in the attack. Aggressive attacks against diplomatic premises do not amount to acts of force against the sender State because those premises are not part of its territory. If, on the other hand, those acts are committed from outside the territory of the receiving State, they may amount to use of force against the latter. In case the receiving State itself is found to be accountable for the incident, then it must be dealt with under the leges speciales of the law on diplomatic relations.
The prohibition of the use of force, as laid down in Art. 2(4) of the UN Charter, only applies to sovereigns thus armed operations by States and against States fall under the provision but private individuals or groups which are not members of the United Nations cannot be addressed by the rule as a matter of treaty law. In State practice, an extension of the rule to bind private actors in their armed operations or to protect them against State operations cannot be said to be accepted. It is, however, accepted that stabilized de facto regimes as pre-State entities are both, obligated and safeguarded by the prohibition
Further, under customary international law, privately acting individuals or groups do not come under the scope of the prohibition of the use of force, even if they may dispose of the financial, military, and organizational strength allowing them to commit acts of armed force against States that have the scale and effects of inter-State operations. In its recent jurisprudence the ICJ made it clear that acts of violence by non-State actors can only become relevant as amounting to an act of armed aggression if they are attributable to a State, which would then rightly become the target of self-defense.
Another way of attributing private actions to a State, holding it responsible under the prohibition of the use of force, is the concept of indirect force. Recent State practices confirm that use of armed force by non-State actors only becomes relevant with regard to the prohibition of the use of force if it can be attributed to a State other than the one affected by it. Private individuals or terrorist groups do not qualify as legal subjects of the rules on the non-use of force, they may, however, be the objects of policing or law enforcement operations, but not the recipients of sincere acts of self-defense.