The UN Charter prohibits the use of force by States subject to limited exceptions. There is disagreement as to the scope of the exceptions.
There is a principle of self-defence, but it is unclear and controversial as to whether it is available only in response to an armed attack or it allows pre-emptive responses to protect nationals in other States or to counter terrorist threats and attacks.
Force has been used by way of so-called humanitarian intervention in certain cases.
International law may seem especially weak in the context of the use of force. The UN has been unable to stop numerous wars and civil wars since its establishment. The League of Nations covenant established after the First World War was unable to prevent the Second World War.
It is the fundamental purpose of the UN to maintain international peace and security and to that end, take effective measures for the prevention and removal of threats to the peace and for the suppression of acts of aggression or other breaches of the peace.
The Security Council was originally established to deal with threats to international peace and acts of aggression. The possibility of dedicated UN forces was contemplated. However, the first 40 years of the United Nations saw the Cold War between the key members of the Security Council, each with a veto, namely, the USA, USSR now Russia, China, France and the UK.
The original Charter proposal for UN army was dropped. However, States have been authorised to use force in cases beyond the scope of the UN to manage. The UN has organised peacekeeping and military force using military and other resources from various States.
Declarations have been adopted on the definition of aggression, friendly relations and the non-use of force. However, there does not exist unanimity between UN members in relation to the scope of self-defence rights.
The UN Charter declares that all member states 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 purpose of the United Nations. The Charter declares the principles applicable even as against non-members of the UN in so far as it is necessary to maintain international peace and security.
The prohibition on the use of force is generally accepted as a fundamental principle of traditional and customary international law. Some states have tried to claim justification for invasions to retake their traditional territory. This has generally been condemned vigorously by the United Nations as inconsistent with the duty to resolve disputes peacefully, without resort to aggression.
Civil War & Self Determination
There was controversy as to what extent the rules apply internally to civil conflicts. The Soviet block took the view that the Vietnamese and Korean Wars were internal, whereas the Western block took the view that an act of aggression was involved.
During the period of decolonisation after the Second World War, many former colonies and dependencies asserted the position that force is permissible under the above principles in pursuit of self-determination. This was objected to, by the former colonial powers at General Assembly.
Ultimately, resolutions in relation to aggression and friendly relations have been ambiguous in their terms recognising a right for groups with self-determination to struggle for that purpose, leaving open the question of whether force could be used. It was accepted that force could not be used against such persons with a right of self-determination.
It is claimed that force may be used to re-establish or pursue democracy. The UN has authorised force to restore democracies which have been overthrown. However, there is no such general principle at the UN level and the matter has remained largely in the political sphere.
There have been a number of instances in the last few decades of intervention on humanitarian grounds. In some instances, this has been done by regional organisations such as NATO. It has been difficult to establish sufficient Security Council support in many instances and political considerations have arisen.
NATO States disagreed with other UN Security Council members in relation to intervention in Kosovo. NATO conducted a campaign which was perceived to be largely successful in ending a humanitarian crisis. In contrast, intervention by a group of countries in Iraq in order to effect regime change, led to a series of catastrophic civil wars.
A number of states from the developed west, have promoted humanitarian intervention without the request of the states concerned, in cases of extreme humanitarian need. There have been a number of instances of intervention by states through the 1970s in other states to end oppressive regimes and in claimed support of self-determination.
Developing States argue that force and coercion extend beyond armed force to economic coercion. The extent to which force may be used to realise national democracy or for other purposes compatible with the UN principles has been controversial.
Not all states have accepted that the violation of human rights justifies the use of force by foreign states. The issues become pointed when the matter arises as part of a quasi-political struggle within a state, where opposition forces are seeking to overthrow the government.
The claimed right of international intervention remains very controversial. It is objected to, by the non-aligned movement. It is open to the criticism that it may be used for political purposes.
The position has been updated in recent years by the concept of responsibility to protect, in accordance with the principles adopted in the UN World Summit Document. The responsibility arises in relation to genocide, ethnic cleansing and serious violations of human rights.
It holds that where a state fails to take necessary action to protect its own citizens, other states have the responsibility to act using force if necessary. The intervention must be approved by the UN Security Council.
The UN Friendly Relations Declaration provides that in relation to civil conflict in other States, there is a duty not to ferment, tolerate, incite or tolerate subversive terrorist or armed activities directed at the overthrow of a regime in another State. This reflects the rights of States to conduct their affairs and choose a form of government internally and has been part of customary international law.
The International Court of Justice found that American support of the “Contras” in Nicaragua violated international law, who sought to overthrow the elected government. Assistance to a government is permissible but assistance to opposition is not permissible.
In some cases, there has been controversy as to whether interventions have been at the request of the government. France has intervened in its former colonies in order to maintain order at their request of the relevant governments on a number of occasions.
If the conflict is such that it is characterised as a Civil War rather than unrest, there is a duty not to intervene without UN or regional authorisation. The principle was claimed by the Soviet Union to apply in respect of their interventions in Czechoslovakia and Afghanistan in 1968 and 1979. However, it was condemned on both occasions by the UN Security Council.
There is a right to use force in self-defence. However, there is controversy regarding the scope of the right. The UN Charter provides that nothing in it 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 the measures necessary to maintain international peace and security.
Measures taken by the member states in the exercise of the right must be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Council under the Charter to take any time such action as it deems necessary to maintain and restore international peace and security.
There is an argument as to the scope of the above right. It is argued that the wording preserves the customary rights of self-defence including that which is argued to include anticipatory self-defence and the protection of nationals abroad.
It is argued to the contrary that this interpretation is so wide as to make the provision meaningless and that, as an exception, it should be interpreted narrowly.
It is agreed that self-defence must be necessary and proportionate. It generally contemplates retaking national territory or repelling attacks. Anticipatory self-defence is controversial.
Armed attack includes invasion but also attacks by the army of one State against a territory or forces, land, sea or air of another. It may include attacks by irregulars and other armed bodies, mercenaries etc. However, an armed attack would not include support by way of the provision of materials or logistical support.
Some States in particular the US and Israel, have purported to use force in protection of their nationals, internationally. This has been controversial and has been used to justify political intervention to overthrow the government. The intervention must be proportionate and necessary.
The most controversial aspect of self-defence is the so-called pre-emptive self-defence. Questions have arisen as to how immediate the threat of attack must be. Some states claim a wider basis of anticipatory self-defence.
On the one hand, it seems plausible that a state should not have to wait for an attack where it is relatively imminent. On the other hand, the principle is clearly open to abuse.
The US-led removal of the Afghanistan Taliban regime after the 9/11 attacks was very widely supported. The Security Council recognised it as an act of self-defence.
Israel has also undertaken a number of military actions, on the alleged basis of pre-emptive defence in relation to Lebanon where the actions were directed against third party fighter, rather than government forces.
Such attacks raise issues of proportionality. Some of the Israeli actions, including invasions of Lebanon have been widely criticised as disproportionate.
Report to Securiy Council
States are to report the use of force for self-defence to the Security Council. The International Court of Justice has taken the view that the failure to report actions might be an acknowledgement that it does not constitute self-defence.
In principle, the right to take measures for self-defence is temporary until the Security Council takes measures to maintain international peace and security. The Security Council does not in fact adjudicate on issues of or deal with claims to self-defence, which may be difficult to determine in cases of mutual hostilities.
It would appear that anything short of a resolution specifically terminating the right to take action would leave the right of action intact, in the case of an invasion and occupation.