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  • Writer's pictureIRALR


This article is written by Muskaan Garg, a 2nd Year law student from SLS, Pune


In the nineteenth and early twentieth centuries, it was the doctrine of bellum justum which was regarded for use of force. This doctrine legitimized violence, in international law, pertaining to a just criterion. The initiation of right of self-defence is closely related to this doctrine. It made the international law regard self-defence a counter war against an illegal war.

In 1928, the situation witnessed a drift with the Kellogg-Briand pact which outlawed the use of force in form of wars. Self-defence then became a critical exception of the same. This prohibition of use of force and renunciation of war was also repeated in the article 2(4) of UN charter. Therefore, today article 2(4) of the charter prohibits use of force while article 51 of the charter renders self-defence as its exception in cases of armed attack.

The caroline incident

The doctrine witnessed its evolution from an incident in 1837-1838 which was the result of brimming resentment of Canada against the British dominance and rule. A Canadian, William Mackenzie occupied the british navy island. The british troops, anticipating danger, set steamboat ‘caroline’ ablaze while it was anchored on American side of the river which resulted in diplomatic issues between Britain and America. The latter was accused of breaching their neutrality regime while the former was accused of violating the territory borders. It was the formal conversation between the diplomats of the nations which brought about the concept of self-defence in format. The American side of the letter stated that in order to justify their actions, Britain needed to prove that there was ‘necessity of self-defence, instant, over whelming, leaving no choice of means and no moment for deliberation’. These exact words held weightage and later resulted into an agreement between these two nations which was not recognized otherwise. Hence, terming the incident as a doctrine is ambiguous as it lacks formal recognition or registration as an internationally accepted clause. The incident is often read as caroline formula or webster’s formula by the nature of specific set of words highlighted by webster.

Contribution of the caroline formula

The caroline formula with all its elements did not make it to the charter but instead its concept was still stay existing with article 51 regarding self-defence as an exception of the prohibition of use of force. Article 51 of the UN charter states that the self-defence is an inherent right when there is an armed attack and the same is notified to the security council. After this codification the right of self-defence split into three possibilities; first being the pre-emptive or preventive self defence used on stimulation of mere threat, second being the anticipatory self-defence used in presence of ‘imminent threat’, and third being the right of self-defence which is inherent during the times of an armed attack as mentioned in the charter.

The basic index of mapping self-defence is the mandatory elements of necessity and proportionality should be present with their threshold attained and the intention behind using the right should be not be malignant. The UN charter aims to maintain all elements of a valid self-defence. It is in times of an armed attack the element of necessity attains threshold while proportionality can be framed according to the force used in the attack and in order to ensure the right intention the charter mentions the mandatory notification of the attack to the security council.

There has been a debate between two perspectives of this argument, namely anticipatory self-defence and self-defence in cases of armed attack both of which are successors to customary law practice and the charter respectively. In case of the former, the index of necessity might or might not attain the threshold whereas proportionality cannot be ascertained as the attack is still anticipated. Similarly, in the case of pre-emptive self-defence both the indexes of necessity and proportionality do not suffice the required threshold and can only be foresighted, hence do not hold valid as an exception of use of force.

In the present there have emerged two broadline perspectives of the legitimacy of the right to self-defence. One stating that the charter is limiting the right of self defence only to scenarios of armed attack which does not include anticipatory self-defence or actions against imminent threats whereas the second stating that the charter, though nowhere mentioned, by expansion and interpretation includes anticipatory self-defence with actions against imminent threats and is not only limited to scenarios of ‘armed attack’. The first perspective gains support on the basis of not being a customary practice as it has not been followed to that extent. The second perspective is supported by the pre-existing norms on self-defence and hence it could be assumed that it refers to the same pre-existing right and has no motive to restrict the same.

Both the perspectives germinate from the same reason of granting the right of self-defence to the states but differ in intensity. It could be understood as a set up of concentric circles wherein the inner ring is closer to the centre and has a narrower scope while the outer one is farther from the centre and has a wider scope. Hence both the rings have the same pivot but different boundaries.

Timeline of application and legality

In the case of Nicaragua v. United States 1986, the court stated that in order to exercise the right of collective self defence, a state should be a victim of an armed attack. It was held that Nicaragua in no way attacked US and therefore the latter’s military and para-military activities did not justify the exception of collective self-defence. In a dissenting opinion, Judge schwebel stated that the word ‘inherent’ within article 51 of the charter prevents complete out-ruling of the customary international law and thus does not intend to confine the scope of the article. Hence in this case, the judgement could be interpreted as one of a restrictive notion wherein the charter limits the right of self-defence to an armed attack. It was in this case that an outline of what constitutes an armed attack rather examples of what could be an armed attack was deliberated.

In the case of Democratic Republic of the Congo v Uganda 2005, court rejected uganda’s claim of using force as an exercise of self-defence as it could not prove that the armed attack had any involvement of congo and neither had the former reported any such attack to the security council. Uganda tried to justify its actions stating preventive measure to prevent breach of security, which is not a legitimate condition for the use of force as per article 51 of the charter. Hence it was held that Uganda could not claim the right to self-defence against congo.

In the case of Israel v. Arab countries 1967, also known as the 6-day war case, Israel launched a surprise attack against Egypt in order to prevent an alleged attack on Israel. This act of pre-emptive self defence led a series of events which ultimately resulted in a war between the arab nations and Israel. Though that by nature it was a preventive strike yet it was believed that egypt’s moving of its army across the sinai, closing port of aqaba and forcing the UN peacekeeping force out of sinai were actions done intentionally to induce a war-like response. Hence the UNSC rejected proposals of condemning Israel for its aggressive actions, instead they adopted a resolution compelling Israel to withdraw from claimed territories and acknowledge the right of every state to live in peace.

In the case of Israel v. Iraqi nuclear reactor 1981, israel destroyed a nuclear reactor of Iraq claiming that the reactor was planned to build nuclear weapons which would be used against Israel and thereby the act of destroying the reactor is justified asserting self-defence. Another contention put forward was that article 51 of the charter does not foresee the use of nuclear weapons and the immense danger posed by such an attack therefore it is justified to stop the attack at this stage of inception itself. The UNSC straight away rejected such contentions and condemned it as an act of aggression in violation of the charter.

The 9/11 terrorist attacks brought about a major change in international affairs regarding self-defence wherein the UNSC for the very first time approved a resolution invoking and reaffirming the right of self-defence, expressing their readiness to take all necessary steps in response to this particular terrorist attack. The US using the resolution to their leverage launched a revenge operation in Afghanistan which did not face any major challenge of legality amongst most nations. In 2001, Iraq invaded Kuwait and did not comply to any resolutions of the UN. Later it also prepared its ballistic missiles and nuclear weapons and delayed compliance to disarmament resolutions as well. After investigation no weapons of mass destruction were found by the UN yet, in 2002-03, US invaded Iraq in order to disarm the state of weapons of mass destruction. The US contended that the mission aimed to disarm the state, end its support for terrorism, free the people of Iraq and justified it by stating that after 9/11 the nation has diverted towards ‘bush doctrine’ which implied dealing with threats before they could harm the state.

In the Nuclear weapon’s case 1996, it was stated that mere possession of nuclear weapons is not illegal and does not of itself constitute a threat but a signalled intention to use such force could constitute a threat of force which is illegal according to Article 2(4). The Court could not reach a definite conclusion upon the legality of the use of nuclear weapons and hence marked it by stating that if the threat will be in violation of article 2(4) and article 51 of the charter then it would be rendered as illegal.

In the Oil platform case 2003, US destroyed off-shore oil production facilities of iran claiming self-defence in response to alleged attack on sea isle city and mining of a naval vessel. Iran’s involvement could not be proved in either attack. The court held that US could exercise the right of self-defence only if it would have been a victim of an armed attack by iran and therefore was not right in attacking oil platforms.


The irregular trend of the legitimacy of various formats of self-defence has on one side made it difficult to assess a concrete legal frame for the right whereas it also indicates the wide scope of the inherent right depending hugely upon the facts and circumstances of each case. Although the contemporary concept of self-defence is complex and confusing, yet, it very well ascertains that maintaining peace and safeguarding the right to peace of every nation is the ultimate goal. The caroline formula and the words stated in the UN charter though different in literal nature and applicability, are very much same in spirit and stem from the same purpose. The purpose of balancing the availability of right of self-defence, prevention of its misuse and safeguarding the right of peace.

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