This article has been written by Mr. Dhruva Ranjan, a second-year student of Christ (deemed to be) University, Delhi NCR. 

 

Abstract

The UN Charter formalized the right to self-defense. The Charter became the official document on self-defense once the majority of the world’s governments signed on. Scholars and government officials quickly began parsing its language for exceptions and justifications that broadened the ability to use force. Bowett 1958 establishes the trend of seeking larger rights than those outlined in the UN Charter. Brownlie 1963 answers with a defense of the UN Charter. Some governments, particularly those in militarily strong states, agreed with Derek Bowett, but the International Court of Justice (ICJ) ruled in 1986, in a case involving the United States and Nicaragua, that the Charter rules on self-defense had become customary international law. The court even cited references from the United States that described the ban on the use of force as a peremptory rule of international law (jus cogens). The ICJ underscored the limitations on self-defense outlined in Article 51 and in general international law beyond the Charter, particularly the criteria of necessity and proportionality. Some government officials and academicians have objected to the Nicaragua v. United States of America ruling (International Court of Justice 1986). They continue to explore the parameters of Article 51, looking for alternatives to deploying force, such as the Anglo-American correspondence from 1841 over the sinking of the Caroline. Despite these attempts, the Nicaragua case has largely retained its authority. Alexandrov 1996 focuses on Nicaragua while also returning to Bowett’s argument for a right to attack under prevailing customary international law. The Charter was once again challenged in the aftermath of the 9/11 terrorist attacks in the United States, when the government proclaimed a global war in self-defense against terrorism. In its 2002 National Security Strategy, the United States declared the right to “preemptive” self-defense against terrorist threats, nuclear weapons programs, and other such dangers. Other historians, like Ian Brownlie in the 1960s, have defended the Charter against the concerns posed by 9/11. In 2005, the UN concluded a two-year assessment of the Charter and its functioning. The final text, World Summit Outcome 2005, reaffirmed the countries’ commitment to strict respect to the Charter requirements. The text provides no more basis for the right to attack in self-defense in circumstances other than an armed attack. Corten 2014 has the same consensus as the result paper, offering a detailed examination of ICJ law on self-defense from 1948 to 2007.

Introduction

Humanity has long acknowledged the right of individuals to protect themselves against aggression. In international law, this underlying normative understanding for nations is established in Article 51 of the United Nations Charter. Article 51 is an exemption to the Charter’s general ban on the use of force, which appears in Article 2(4). The Charter’s restriction on the use of force is central to its purpose, which is to “save succeeding generations from the scourge of war” (Preamble). It seems to reason that any right to use force as an exception to the general prohibition against resorting to force would be limited. Article 51 allows a state to use unilateral or collective self-defence only “if an armed attack occurs.” This article discusses the international law exemption to the ban on using force for self-defence. The commentary on Article 51 is extensive and generally falls into two categories: first, scholarship, judicial decisions, and government policies that support the plain terms of the article; and second, scholarship and government policies that advocate expanding the right to use force beyond the provisions of the article. The authors in these two groups go by numerous names, but they are most generally referred to as “strict” interpreters and “broad” interpreters. One author refers to the factions as “restrictivists” and “antirestrictivists.” The disparity in views can be explained in part by the authors’ varied perceptions of the value of using armed force. The UN Charter was created near the close of World War II, when trust in military power was low and there was a strong desire to cease the use of force. Fifty years later, possibly exasperated by the failure of other tactics, authors (particularly in a few militarily powerful governments) proposed easing the prohibitions against using force to respond to terrorism, weapons programs, and computer networks. Some attempt to justify force using the criteria of necessity and proportionality, which go beyond the UN Charter but are as essential in the long history of normative thinking on killing in self-defence. 

It is widely agreed that using force in self-defense is legal under modern international law, but numerous views have emerged in recent decades on the nature and scope of this right. Most legal academics believe that the right to self-defense is triggered by an armed attack on a state for which another state is liable, and that it is only permissible to repel the attack or eliminate its effects, such as ending occupation. Others, however, have advocated for a broader definition of self-defense, which includes: 

pre-emptive attacks in the face of frightening military preparations ‘to suppress any prospect of future attack by another State, even where there is no cause to suspect that an attack is intended and when no prior assault has happened’ (so-called pre-emptive, or preventative, self-defense).; 

(ii) the use of force against troops, planes, vessels, or installations in the event of threats likely to result in imminent attacks, particularly when the State resorting to force has already suffered an armed attack and fears that more attacks are being prepared (anticipatory self-defence); and 

(iii) the use of force by a state whose territory or military assets are ostensibly the target of an attack already launched by another state, in order to halt the attack.

Even assuming that force is only legal as a response to an armed attack, the question of the duration of the armed response arises, namely, whether a state that has been attacked is only authorized to use force to repel the attack or whether the state is also entitled to use retaliatory force as a deterrent to future attacks from the same source.

The International Court of Justice (ICJ) recently heard a case regarding self-defence. On November 6, 2003, the Court issued a decision in the Case Concerning Oil Platforms (Iran v. United States of America), in which the Court considered a dispute arising from the attack and destruction of three offshore oil production complexes owned and operated for commercial purposes by the National Iranian Oil Company by several US Navy warships on October 19, 1987, and April 18, 1988, respectively. The applicant relied solely on the compromissory clause included in Article XXI(2) of a bilateral treaty between these countries, namely the Treaty of Amity, Economic Relations, and Consular Rights, signed in Tehran on 15 August 1955 and entered into force on 16 June 1957 (the 1955 Treaty). Although the ICJ’s primary role on the merits was to rule on the parties’ violations of freedom of trade and navigation, the Court spent a significant amount of time debating whether the United States’ actions could be justified as valid self-defense measures. Ultimately, the Court held that:

This conclusion is given in the first section of the dispositif of the decision. In the second part, the Court determined that the United States’ actions did not constitute a breach of its obligations under Article X(1) of the Treaty regarding freedom of commerce between the parties’ territories, and that the Islamic Republic of Iran’s claim for reparation could not be upheld. This article examines the judgment’s contribution to international law on the use of force in self-defense, focusing on two topics: first, the relationship between self-defense and the protection of states’ essential security interests, as embodied in Article XX(1)(d) of the 1955 Treaty, and second, an analysis of the conditions of self-defense in the current dispute. The study must be situated within the ongoing political and intellectual debate about the circumstances and limitations of the use of force in international affairs.

PRINCIPLES OF INTERNATIONAL LAW ON SELF-DEFENCE

The Charter of the United Nations prohibits the use of force against another state except where the Security Council has authorised the use of force to maintain or restore international peace and security; and where a state is exercising its inherent right of individual or collective self-defence recognised by Article 51 of the Charter. 

The principles set out below are intended to provide a clear statement of international law regarding the inherent right of self-defence. All the principles need to be read together. Even in a case where a state is legally entitled to use force, there may be reasons of prudence and principle not to exercise that right. The law on self-defence encompasses more than the right to use force in response to an ongoing attack.

Article 51 preserves the right to use force in self-defence “if an armed attack occurs”, until the Council has taken the necessary measures. On one view, the right is confined to circumstances in which an actual armed attack has commenced. But the view that states have a right to act in self-defence in order to avert the threat of an imminent attack – often referred to as ‘anticipatory self-defence’ – is widely, though not universally, accepted. It is unrealistic in practice to suppose that self-defence must in all cases await an actual attack. 

The ‘armed attack’ may include not only an attack against a state’s territory, but also against emanations of the state such as embassies and armed forces.

Force in self-defence may be used only when: the attack consists of the threat or use of force (not mere economic coercion, for example); when the attacker has the intention and the capability to attack; and the attack is directed from outside territory controlled by the state.

In the case of a threatened attack, there must be an actual threat of an attack against the defending state itself. The inherent right of self-defence recognised in Article 51 of the Charter of the United Nations “if an armed attack occurs” forms an exception to the general prohibition against the use of force under Article 2(4). 

For the purpose of Article 51, an armed attack includes not only an attack against the territory of the State, including its airspace and territorial sea, but also attacks directed against emanations of the State, such as its armed forces or embassies abroad. An armed attack may also include, in certain circumstances, attacks against private citizens abroad or civil ships and airliners. An ‘armed attack’ therefore is an intentional intervention in or against another state without that state’s consent or subsequent acquiescence, which is not legally justified.

An armed attack involves the use of armed force and not mere economic damage. Economic damage, for example, by way of trade suspension, or by use of a computer virus designed to paralyse the financial operations of a state’s stock exchange or to disable the technology used to control water resources, may have a devastating  impact on the victim state but the principles governing the right to use force in self-defence are confined to a military attack. A purely ‘economic’ attack might however give rise to the right of self-defence if it were the precursor to an imminent armed attack. 

An armed attack means any use of armed force, and does not need to cross some threshold of intensity. Any requirement that a use of force must attain a certain gravity and that frontier incidents, for example, are excluded is relevant only in so far as the minor nature of an attack is prima facie evidence of absence of intention to attack or honest mistake. It may also be relevant to the  issues of necessity and proportionality.  In the case of attacks by non-State actors, however, different considerations may come into play. 

The term ‘armed attack’ requires the attacker to have the intention to attack.  In the Oil Platforms Case the ICJ made reference to this requirement when it inquired into the question whether the US was able to prove that certain of Iran’s actions were “specifically aimed” at the US or that Iran had “the specific intention” of harming US vessels.  But to the extent that this may be read as suggesting that military attacks on a state or its vessels do not trigger a right of self-defence as long as the attacks are not aimed specifically at the particular state or its vessels but rather are carried out indiscriminately, this part of the ICJ’s ruling in Oil Platforms has been criticised as not supported by international law. 

An armed attack is an attack directed from outside territory controlled by the State.  In its Advisory Opinion on the Legal Consequences of the Construction of a Wall in the Occupied Palestinian Territory the ICJ’s observations may be read as  reflecting the obvious point that unless an attack is directed from outside territory under the control of the defending state the question of self-defence in the sense of Article 51 does not normally arise. 

In the case of a threatened attack, there must be an actual threat of an attack against the defending state itself, whether directed against that state or by an indiscriminate attack.This is an aspect of the criterion of necessity. It addresses the question whether it is necessary for the target state to take action

3. Force may be used in self-defence only when this is necessary to bring an attack to an end, or to avert an imminent attack. There must be no practical alternative to the proposed use of force that is likely to be effective in ending or averting the attack.

The criterion of necessity is fundamental to the law of self-defence. Force in self-defence may be used only when it is necessary to end or avert an attack.  Thus, all peaceful means of ending or averting the attack must have been exhausted or be unavailable. As such there should be no practical non-military alternative to the proposed course of action that would be likely to be effective in averting the threat or bringing an end to an attack. Necessity is a threshold, and the criterion of imminence can be seen to be an aspect of it, inasmuch as it requires that there be no time to pursue non-forcible measures with a reasonable chance of averting or stopping the attack.

 

Necessity is also a limit to the use of force in self-defence in that it restricts the response to the elimination of the attack and is thus linked to the criterion of proportionality. The defensive measure must be limited to what is necessary to avert the on-going attack or bring it to an end. 

In applying the test of necessity, reference may be made to the means available to the state under attack;  the kinds of forces and the level of armament to hand will be relevant to the nature and intensity of response that it would be reasonable to expect, as well as the realistic possibilities of resorting to non-military means in the circumstances.

4. A state may use force in self-defence against a threatened attack only if that attack  is ‘imminent’.

There is a risk of abuse of the doctrine of anticipatory self-defence, and it needs to be applied in good faith and on the basis of sound evidence. But the criterion of imminence must be interpreted so as to take into account current kinds of threat and  it must be applied having regard to the particular circumstances of each case. The criterion of imminence is closely related to the requirement of necessity.  

Force may be used only when any further delay would result in an inability by the threatened state effectively to defend against or avert the attack against it. 

In assessing the imminence of the attack, reference may be made to the gravity of the attack, the capability of the attacker, and the nature of the threat, for example if the attack is likely to come without warning. 

Force may be used only on a proper factual basis and after a good faith assessment of the facts.

The concept of ‘imminence’ reflects the Caroline formulation of ‘instant, overwhelming, leaving no choice of means, and no moment for deliberation’. In the context of contemporary threats imminence cannot be construed by reference to a temporal criterion only, but must reflect the wider circumstances of the threat.

There must exist a circumstance of irreversible emergency. Whether the attack is ‘imminent’ depends upon the nature of the threat and the possibility of dealing effectively with it at any given stage. Factors that may be taken into account include: the gravity of the threatened attack – whether what is threatened is a catastrophic use of WMD; capability – for example, whether the relevant state or terrorist organisation is in possession of WMD, or merely of material or component parts to be used in its manufacture; and the nature of the attack – including the possible risks of making a wrong assessment of the danger. Other factors may also be relevant, such as the geographical situation of the victim state, and the past record of attacks by the state concerned.

The criterion of imminence requires that it is believed that any further delay in countering the intended attack will result in the inability of the defending state effectively to defend itself against the attack. In this sense, necessity will determine imminence: it must be necessary to act before it is too late. There is a question as to whether ‘imminence’ is a separate criterion in its own right, or simply part of the criterion of ‘necessity’ properly understood. As an additional criterion however, it serves to place added emphasis on the fact that a forcible response in these circumstances lies at the limits of an already exceptional legal category, and therefore requires a correspondingly high level of justification. 

To the extent that a doctrine of ‘pre-emption’ encompasses a right to respond to threats which have not yet crystallized but which might materialise at some time in the future, such a doctrine (sometimes called ‘preventive defence’) has no basis in international law. A fatal flaw in the so-called doctrine of prevention is that it excludes by definition any possibility of an ex post facto judgment of lawfulness by the very fact that it aims to deal in advance with threats that have not yet materialised.

Each case will necessarily turn on its own facts. A forceful action to disrupt a terrorist act being prepared in another state might, depending upon the circumstances, be legitimate; force to attack a person who may in the future contemplate such activity is not. 

The determination of ‘imminence’ is in the first place for the relevant state to make, but it must be made in good faith and on grounds which are capable of objective assessment. Insofar as this can reasonably be achieved, the evidence should be publicly demonstrable. Some kinds of evidence cannot be reasonably produced, whether because of the nature or source, or because it is the product of interpretation of many small pieces of information. But evidence is fundamental to accountability, and accountability to the rule of law.  The more far-reaching, and the more irreversible its external actions, the more a state should accept (internally as well as externally) the burden of showing that its actions were justifiable on the facts. And there should be proper internal procedures for the assessment of intelligence and appropriate procedural safeguards.

The exercise of the right of self-defence must comply with the criterion of ‘proportionality’. The force used, taken as a whole, must not be excessive in relation to the need to avert or bring the attack to an end. The physical and economic consequences of the force used must not be excessive in relation to the harm expected from the attack.

The ICJ has confirmed that it is a well-established rule of customary international law that a use of force in self-defence must be “proportional to the armed attack and necessary to respond to it.” This requires that the level of force used is not greater than that necessary to end the attack or remove the threat. As such it is another way of looking at the requirement of necessity. 

The proportionality requirement has been said to mean in addition that the physical and economic consequences of the force used must not be excessive in relation to the harm expected from the attack. But because the right of self-defence does not allow the use of force to ‘punish’ an aggressor, proportionality should not be thought to refer to parity between a response and the harm already suffered from an attack, as this could either turn the concept of self-defence into a justification for retributive force, or limit the use of force to less than what is necessary to repel the attack.

 

 The force used must take into account the self-defence operation “as a whole”.  It does not relate to specific incidents of targeting (which is a matter for international humanitarian law).  Thus, in the Oil Platforms Case, the ICJ stated that in assessing proportionality, it “could not close its eyes to the scale of the whole operation”. 

6. Article 51 is not confined to self-defence in response to attacks by states. The right of self-defence applies also to attacks by non-state actors.

In such a case the attack must be large scale. If the right of self-defence in such a case is to be exercised in the territory of another state, it must be evident that that state is unable or unwilling to deal with the non-state actors itself, and that it is necessary to use force from outside to deal with the threat in circumstances where the consent of the territorial state cannot be obtained.

Force in self-defence directed against the government of the state in which the attacker is found may be justified only in so far as it is necessary to avert or end the attack, but not otherwise. There is no reason to limit a state’s right to protect itself to an attack by another state. The right of self-defence is a right to use force to avert an attack. The source of the attack, whether a state or a non-state actor, is irrelevant to the existence of the right. The ICJ Wall Advisory Opinion should not be read as suggesting that the use of force in self-defence is not permissible unless the armed attack is by a state. There is nothing in the text of Article 51 to demand, or even to suggest, such a limitation. This conclusion is supported by reference to the Caroline case; the criteria in Caroline were enunciated in the context of a marauding armed band, not orthodox state-to-state conflict. 

State practice in this field, including the recent practice of the Security Council, gives no support to the restriction of self-defence to action against armed attacks imputable to a state; indeed there is state practice the other way.  The action against Al Qaeda in Afghanistan in October 2001 (which was widely supported by states) was action in self-defence of anticipated imminent terrorist attacks from Al Qaeda, not from the Taliban.  It was necessary to attack certain elements of the Taliban, in order to pre-empt attacks from Al Qaeda.  Security Council resolutions 1368(2001) and 1373(2001) support the view that self-defence is available to avert large-scale terrorist attacks such as those on New York and Washington on 11 September 2001.  So too do the invocations by NATO and the OAS of their respective mutual defence obligations

 

The right of states to defend themselves against ongoing attacks, even by private groups of non-state actors, is not generally questioned. What is questioned is the right to take action against the state that is the presumed source of such attacks, since it must be conceded that an attack against a non-state actor within a state will inevitably constitute the use of force on the territorial state. It may be that the state is not responsible for the acts of the terrorists, but it is responsible for any failure to take reasonable steps to prevent the use of its territory as a base for attacks on other states. Its inability to discharge the duty does not relieve it of the duty. But the right to use force in self-defence is an inherent right and is not dependent upon any prior breach of international law by the state in the territory of which defensive force is used.

Thus, where a state is unable or unwilling to assert control over a terrorist organisation located in its territory, the state which is a victim of the terrorist attacks would, as a last resort, be permitted to act in self-defence against the terrorist organisation in the state in which it is located. 

The same criteria for the use of force in self-defence against attacks by states are to be used in the case of attacks by non-state actors, but particular considerations are relevant. The attack or imminent attack by non-state actors must be large-scale.  

For action in self-defence to be ‘necessary’, it must first be clear that measures of law-enforcement would not be sufficient. To show the necessity of action against the territory of another state not directly responsible for the acts of the non-state group requires, inter alia, the demonstration that there is no other means of meeting the attack and that this way will do so. Terrorist organisations are not easily rooted out by foreign armed forces. 

Where, therefore, the attack is not ongoing but imminent, the territorial state is entitled to proceed in its own way against the group on its territory. In this context, the requirement of ‘imminence’ means that action in self-defence by another state may not be taken save for the most compelling emergency.

7. The principles regarding the right of self-defence form only a part of the international regulation of the use of force. 

Measures taken in the exercise of the right of self-defence must be reported immediately to the Security Council. The Council retains the right and responsibility to authorise collective military action to deal with actual or latent threats.  

Any military action must conform with the rules of international humanitarian law governing the conduct of hostilities.

 

Conclusion

It delves into the historical context, major cases, and contemporary challenges that have shaped the interpretation and application of Article 51 of the United Nations Charter.

The UN Charter, a pivotal document in international law, established the right to self-defense while simultaneously imposing a general ban on the use of force to prevent the scourge of war. The article meticulously traces the trajectory of legal discourse on this right, beginning with early challenges to the Charter’s restrictions by scholars like Derek Bowett in 1958. The debate between those advocating for a broader interpretation of self-defense, such as Bowett, and those defending the Charter’s principles, exemplified by Brownlie in 1963, set the stage for subsequent legal developments.

The watershed moment came in 1986 with the Nicaragua v. United States of America case, where the ICJ ruled that the Charter’s rules on self-defense had crystallized into customary international law. This landmark decision reinforced the limitations outlined in Article 51, emphasizing the criteria of necessity and proportionality. Despite objections and ongoing exploration of alternatives, the Nicaragua case has retained its authority, providing a significant foundation for subsequent legal discussions.

The article then navigates through key historical events, such as the aftermath of the 9/11 terrorist attacks and the subsequent U.S. declaration of a global war in self-defense against terrorism. The controversial notion of “preemptive” self-defense against potential threats, including nuclear weapons programs, raised important questions about the scope and limitations of self-defense. The United Nations’ World Summit Outcome in 2005 reaffirmed strict adherence to Charter requirements, emphasizing the need for a justifiable basis for the use of force in self-defense.

The author also highlights the ICJ’s more recent involvement in the Case Concerning Oil Platforms (Iran v. United States of America), where the Court evaluated the U.S. actions in the attack and destruction of Iranian oil platforms. This case provided an opportunity for the ICJ to contribute to the evolving understanding of self-defense, particularly regarding the relationship between self-defense and the protection of states’ essential security interests.

The principles of international law on self-defense, as outlined in the article, serve as a guide for interpreting and applying Article 51. These principles emphasize the necessity for an armed attack to trigger the right to self-defense, the consideration of imminence, and the crucial criteria of proportionality. The article stresses the importance of these principles in responding not only to attacks by states but also by non-state actors, acknowledging the evolving nature of contemporary threats.

The comprehensive analysis extends to considerations of necessity, emphasizing that force must only be used when there is no practical alternative likely to be effective in averting the attack. The criterion of imminence is explored in detail, underlining its role in justifying a forcible response at the limits of an already exceptional legal category. The principles of proportionality further guide the evaluation of the appropriateness of force used in self-defense.

Crucially, the article addresses the application of these principles to attacks by non-state actors, making a case for the justifiability of self-defense when a state is unable or unwilling to control a terrorist organization within its territory. It asserts that the right of self-defense is inherent and not dependent on prior breaches of international law by the state in whose territory defensive force is used.

The conclusion drawn from the extensive analysis is that the principles of self-defense form only a part of the broader international regulation of the use of force. Any measures taken under the right of self-defense must be reported to the Security Council, which retains the authority to authorize collective military action to address actual or latent threats. Additionally, any military action must adhere to the rules of international humanitarian law governing the conduct of hostilities.

The article provides a nuanced and detailed examination of the evolving legal standards surrounding the right of self-defense in international law. It underscores the delicate balance between the imperative to protect nations from aggression and the necessity to prevent the misuse of force. The principles outlined serve as a crucial framework for interpreting and applying the right of self-defense in a complex and rapidly changing geopolitical landscape. As the international community continues to grapple with contemporary challenges, this analysis contributes to the ongoing dialogue on the appropriate use of force and the maintenance of global peace and security.

 

References

1. This article was originally written by Gray Christine published on Oxford Academic website. The link for the same is herein. https://academic.oup.com/book/10167/chapter-abstract/157745615?redirectedFrom=fulltext
2. This article was originally written by Chatham House published on Chatham House website. The link for the same is herein. https://www.chathamhouse.org/sites/default/files/public/Research/International%20Law/ilpforce.doc
3. This article was originally written by Mary Ellen published on Oxford Bibliographies website. The link for the same is herein. https://www.oxfordbibliographies.com/display/document/obo-9780199796953/obo-9780199796953-0028.xml
4. This article was originally written by Robert H. McKinney published on McKinney Law website. The link for the same is herein. https://mckinneylaw.iu.edu/iiclr/pdf/vol19p1.pdf
5. This article was originally written by Albert Camus published on Medecins Sans Frontieres website. The link for the same is herein. https://guide-humanitarian-law.org/content/article/3/self-defense/#:~:text=168.,United%20States%20of%20America%20%2C%20paras.