The State’s Duty of Self-defence: Justifying the Expansion of Criminal Law

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The State’s Duty of Self-defence: Justifying the Expansion of Criminal Law




IN RESPONSE TO the rise of terrorism in recent years, many governments have reviewed the criminal measures they employ against those involved in terrorist activities within their borders. New laws have been put into place granting more powers to the various authorities involved in the fight against terrorism, both in terms of loosening the strict rules governing criminal procedures and in terms of developing new and far-reaching criminal offences. The creation of new criminal offences has been accompanied by two types of debate: the first questions the necessity and efficacy of these offences, and the second focuses on their moral permissibility and their tendency to expand the criminal law beyond its previously recognised boundaries. The underlying fear that has triggered both types of debate is that these new state powers will have negative implications for individual liberties.1 At the same time, it is essential to explore the possibility that in some situations, the creation of new offences may be justified in order to enhance security. In light of the political rhetoric surrounding the extension of the criminal law2 and the fear of misuse of the ‘security’ reasoning, it is vital to develop clear philosophical frameworks that can be used as benchmarks against which to assess these assertions.

This chapter concentrates on the second of these debates—the moral permissibility of new criminal offences—by developing a moral justification for certain expansions of the substantive criminal law. It should be stressed that this chapter is concerned with the use of criminal law in ‘ordinary’ conditions, as opposed to its use in ‘states of emergency’. The declaration of ‘a state of emergency’ may put on hold many of the general principles that govern and subsequently limit criminal law in a democracy. Yet, some Western countries such as the United States and the United Kingdom have not declared states of emergency following terrorist attacks within their borders,3 with the result that general principles ought to continue to govern and restrict state coercion, including the use of criminal law.4

Ordinarily, criminal law is governed by the harm principle together with its two supporting principles: the minimalist principle and the principle of fair imputation.5 These principles limit the reach of criminal law to prohibitions of conduct that causes direct (and serious) harm. At times, however, criminal law extends its reach beyond these limitations. Such extensions are usually regarded as exceptions to the general rule, based on the seriousness and the gravity of the potential harm. With increased attention on fighting terrorism, however, some have argued for the need to extend the criminal law based on ‘the state’s right to defend itself against terrorism’. The question, of course, is whether a state’s right to defend itself is a sound basis on which to ground further exceptional extensions to criminal law. Do democratic states have a right to self-defence against their own citizens? And assuming they do, what justifies that right? What are the implications of that right? And what are its limits? This chapter explores what is entailed by the concept of ‘self-defence’ and suggests one way in which it is capable of grounding or justifying a limited extension of criminal law. In answering the above questions it argues for a justification of self-defence that is not a straightforward claim of a state’s right of self-defence. Instead, it is based on a duty of the state that derives from the citizens’ right of self-defence, where such a right exists. The advantage of such a justification is that it reconciles at least some of the exceptions to the general rule that only conduct causing direct harm may be criminalised, while providing clear moral boundaries to the creation of new exceptional offences.

The first section of this chapter reviews the existing law concerning the treatment of exceptions to the general rules limiting criminalisation. It begins by describing the criminalisation of remote harm and examining two ways of understanding claims of self-defence. It is then suggested that the state’s claim of self-defence derives from the individual’s right of self-defence. Section II presents an overview of the individual’s right of self-defence and its internal limitations: the conditions of unjust threat, necessity, imminence and proportionality. Section III suggests one explanation for the connection between the individual’s right of self-defence and the state’s duty of self-defence. This explanation is rejected as unsatisfactory, and in section IV, a second explanation is developed, arguing that the individual’s right to self-defence is triggered not only by a threat to one’s life but also by a threat to one’s liberty. In addition, an attempt is made to justify the state’s duty by appealing to the individual’s core right and liberty-extended right of self-defence. Three possibilities are considered: (a) a state’s duty of self-defence that corresponds to the individual’s right (similar to the duty of unspecified third persons); (b) a duty that is part of the general duty of care (similar to the duty of third parties who owe special duties of care, such as parents to their children); and (c) a duty that derives from the individual right that is also a just course of action in these circumstances, which is transformed into a duty in the shift from the individual to the state. The first two possibilities are rejected in favour of the third explanation that is defended as the most accurate description of the state’s duty. Section V explains how the duty of self-defence justifies extending the scope of criminal law, even though the individual’s right of self-defence has a very limited scope. The concluding section presents some general observations about possible implications of the state’s duty of self-defence and about the types of threats that might trigger it.


The harm principle, together with its accompanying minimalist principle, is commonly understood to stipulate that only conduct causing direct harm to others should be criminalised. Most Western legal systems nevertheless contain criminal prohibitions on some conduct that does not cause direct harm. Offences that criminalise conduct resulting in remote harm are usually justified by the overriding consideration of the dangerousness of a potential remote harmful result. Such offences do not comply with the minimalist principle. The exception is justified because the primary concern of criminal law is the prevention of harm rather than its occurrence.6 The guiding rationale is that the more important the interest, the more protection it should receive. Hence, the proscribed conduct can be further away from the direct harmful results.

Instead of the grounds for such offences being based on overriding considerations of dangerousness (hereafter: the dangerousness consideration), it is submitted that at least some of these exceptions can be justified by reference to the concept of self-defence. Claims of national self-defence, as frequently invoked by executive officials and legislators, can be understood in two ways. One way is to view the reference to the idea of self-defence loosely, as pointing to the need to respond to a serious threat. The concept of self-defence is used only to stress the gravity of the threat and does not refer to the ‘narrow’ concept of self-defence recognised in criminal law, that is, a defender’s right to use violence against an offender under strict conditions. Understood this way, such claims of self-defence have nothing new to add. They are merely rephrasing the overriding consideration of prevention in response to the dangerousness of a potential harm.

A second way of understanding these claims takes them more seriously, as referring to the right of self-defence and to its moral justification as a source of moral permission to use force. Such claims are both wider and narrower than the dangerousness consideration. They are wider because, if sustainable, they may allow the criminalisation of some acts even beyond the currently recognised boundaries of criminal law, which extend to some forms of remote harm subject to the principle of fair imputation and the minimalist principle.7 Indeed, the essence of bringing up this claim is to allow for further extension of criminal law. At the same time, it is narrower than the dangerousness consideration because only some of the threatening conduct currently proscribed on the basis of the dangerousness consideration would fall into the category of threats that may trigger some right of self-defence. The question then is: can claims of self-defence set a basis for an extension of criminal law?


Can the right of self-defence, advanced by the state, justify the extension of criminal law? The state might have a right to defend itself, but the argument is that a more stringent claim can be made—one that entails a prima facie duty. This duty, however, is not a simple one. The state’s claim of self-defence can be understood as a duty owed by the state to its citizens to defend them. The claim for a prima facie duty of self-defence, or more accurately, a duty to defend its citizens, is stronger as it may require the state to act whereas a mere right of self-defence only permits state action. This chapter will concentrates on this second claim of self-defence as a duty, leaving for another time the discussion of possible claims for a right of self-defence.8 This position, which grounds the state’s claim of self-defence in the individual citizens’ right of self-defence, is far from trivial.

The starting point is the understanding of the individual right of self-defence. Legal systems are based on the idea of monopolisation of coercion. Only the state is permitted to use force against its people, to prevent them from harming and violating the interests of others and to punish those who have violated the law. Nevertheless, it is accepted that there may be situations in which the infliction of harm on an individual is imminent, and the only way to avoid it is by using force against those who threaten to inflict the harm. In such situations, legal systems may recognise a right of individuals to use force to defend themselves. Note that the law of self-defence is found in criminal law only because it provides an exemption from the general rule that prohibits the killing (or injuring) of another. This exemption gives a defender permission to resist, repel or ward off an oncoming attack. It does not permit a defender to engage in ‘private punishment’ or other forms of retribution.9

The limited purpose of the right to self-defence is reflected in the internal conditions that govern its legitimate use. By general consensus, self-defence is triggered only under the following four conditions: (a)1. unjust threat; (b)2. necessity; (c)3. imminence; and (d)4. proportionality. One has a right to self-defence only when presented with an unjust threat that is imminent and that necessitates the use of force in response, and such force must be proportional to the potential harm that would have been inflicted. The details of these conditions are somewhat controversial. Compliance with all four, however, is essential for a defensive act to be regarded as an act of self-defence.

1. Unjust Threat

The notion of unjust threat is the root of various justifications of self-defence, and for that reason, it has attracted a great deal of controversy, most notably in the debate among theorists who justify the right of self-defence on the basis of ‘the rights theory’.10 The central question in that debate is what actions give rise to the right of self-defence. The commonly accepted view is that the unjust threat triggers the right. According to this view, the scope of the right to self-defence includes the use of force in response to non-culpable and non-agent aggressors.11 The right of self-defence is triggered by the unjust act of aggression aimed at the defender. Thus the right cannot be asserted against an innocent bystander, who does not pose such a threat.12

At the other end of the spectrum, David Rodin advances the view that it is the unjust aggressor that triggers the right to self-defence; the key is the moral-fault component of the aggressor’s conduct.13 This approach establishes a narrow right of self-defence that covers only the use of force against culpable aggressors. One of the problems with this position is that it might be interpreted to mean that self-defence has some role in punishment (even if only a minor one). However, punishment is founded on different principles and is aimed at achieving distinct ends, none of which are consistent with the reasons on which the defender may act.14

2. Necessity

The requirement of necessity is often viewed as the most important requirement for a claim of self-defence. It addresses two questions. The first is: when may force be used? To which the answer is: only when it is necessary, that is, only as a last resort. The second question is; how much force may be used? The answer to that question is: only that amount necessary to resist the attack.

The necessity requirement raises two related issues: the first concerns the need to retreat, and the second involves the defender’s right to go about his or her own business. In some states, the law does not demand that the defender retreat in the face of an imminent threat. Two types of reasons have been given to justify the lack of mandatory retreat. The first is ‘right reasoning’, or the view that right should never yield to wrong, and the second is ‘honour reasoning’, which holds that it would be disgraceful for a person to run away from danger.15 The response to ‘right reasoning’ is that the freedom of movement and action enjoyed by law-abiding citizens ought to give way when the life of a human being is at stake.16 As for ‘honour reasoning’, it is worth pointing out that sparing a person’s life cannot be compared with maintaining a person’s honour.

The only exception to the rule of retreat is when the attack is taking place in one’s home. Here, contrary to the general rule, the common law follows psychological feelings that ‘a person’s home is their castle’ and thus deserves greater protection.17 Unlike the demand to withdraw in the face of an imminent attack, a person is not required to refrain from going about his or her own business in anticipation of possible danger. The freedom of law-abiding citizens has a favoured status so as to allow them to continue acting lawfully and move around freely instead of limiting their movement in early attempts to avoid danger.

3. Imminence

A condition of the legitimate exercise of self-defence is that the danger triggering it must be imminent. If the threat is not imminent the defender has to pursue an alternative line of action (eg, turning to the authorities for help). Although this requirement stands on its own, its underlying reasoning suggests that it is derived from the requirement of necessity. Only when a threat is imminent is the use of force necessary (and hence permitted).18

The imminence requirement raises the question of pre-emptive defensive action. Most natural law theorists hold that (within civil society) a pre-emptive attack is permitted as an act of self-defence when the anticipated attack is immediate—for example, when the aggressor has already taken up a weapon. Preemptive attack is not permitted when based on mere suspicion and fear.19 Although this condition is commonly accepted, in recent years the understanding of the condition as requiring an immediate or close connection in time between any pre-emptive defensive response and a potential attack (hereafter: immediacy) has attracted much criticism, especially in connection with battered women who kill their abusive partners while the partners are sleeping.

To understand this criticism, consider a hostage held by kidnappers. The hostage is told that she will probably be executed within a week. The history of the kidnappers, as known to the hostage, demonstrates that there is a good chance they will kill her. The hostage finds herself alone with only one guard who has fallen asleep. Her only chance of escape is to kill the guard, who will otherwise call for help when he awakes.20 The threat posed to the hostage cannot be deemed immediate because she still has an entire week before she will be killed. However, the threat is imminent considering that this is probably her last chance to escape. Can it be said, then, that killing the guard is not an act of self-defence merely because the threat to the hostage’s life was not an immediate one? In such situations where the threat is ‘all over’ the defender, there is a ‘second-order threat’, that is, the threat that, when the aggressor initiates an anticipated and highly probable attack, the danger will be inescapable and the defender will not be able to resist, repel or ward off the attack. This second-order threat makes the first-order threat imminent, and it is this characteristic of the first-order threat that justifies the use of force even though the threat is not immediate.21

This modified imminence requirement is founded on the principle underlying the requirement of immediacy, namely, that human life is valuable and should be maintained as long as possible. Joshua Dressler has observed that in recognising the problems faced by battered women while keeping faithful to the value of human life, the American Model Penal Code expanded the right to self-defence to include attempts to avoid harm, even when that harm is not immediately forthcoming. It did so by changing the requirement of ‘imminence’ to ‘immediate necessity’.22 Yet this definition still falls short of the definition offered by Aileen McColgan, who claims that recognising self-defence in the situations discussed above conforms with the ‘lesser harmful results’ theory: if a defender has to wait for the anticipated attack in order to use force, then society gains nothing, and the risk of being killed unjustly falls solely on the defender.23

Jeremy Horder suggests yet another definition of imminence, which would balance the risk of being killed unjustly by requiring ‘a fair and reasonable opportunity to do otherwise’. Whereas the requirement of immediacy shifts the burden of risk from the aggressor to the defender, and only a subjective requirement of fair opportunity (ie, in cases of putative self-defence) would shift the risk to the aggressor, Horder’s requirement gives equal treatment to both.24 In so doing it follows the need to preserve human life.25 This interpretation is more flexible and is consistent with the position that the requirement of imminence is merely one element of necessity. Ultimately, the defender has to prove that the use of defensive force was necessary, and no other less harmful alternative was available to her. This interpretation is appealing and, as will be explained below, has an important implication when applied to the state’s duty of self-defence.

4. Proportionality

The final requirement of claims of self-defence is that of proportionality. The condition is that in the worst situations any harm inflicted on the aggressor must not exceed the potential harm that the aggressor would have inflicted on the defender. Thus a defender may not break an attacker’s legs even if this is the only way to avoid getting a ‘black eye’.

The proportionality requirement raises the question of what interests fall within the scope of self-defence. Natural law theorists have differentiated between the state of nature and civil society. In a state of nature the right to self-defence extends to acts taken to protect one’s life, physical integrity, personal freedom and property. Hobbes justified this expansive view of self-defence by appealing to the liberty each individual has to do everything within his or her power.26 For Locke, the fact that the aggressor does not respect the defender’s right to property means the defender cannot be sure that his or her right to life and freedom will be respected.27

In civil society, however, the right is much more limited. It is generally agreed that the right of self-defence extends to resisting aggressors who threaten one’s life or who threaten the infliction of severe physical injury. (This right shall be called hereafter the core-right to self-defence or core-right.) But that agreement does not reach the protection of freedom and property. Pufendorf argues that there is no right to use force in the defence of property itself, unless the thief threatens the life of the defender. In other words, Pufendorf holds that there is no right to self-defence to protect property, only to protect life, and he accepts that life may be threatened in the course of a robbery.

Locke took this position one step further. He claimed that although self-defence cannot be used against a thief who has stolen ‘all that I am worth’, defensive force may be used against the thief because of the implicit threat the thief poses to the life of the defender. That is, even if the thief does not threaten the life of the defender directly, the force used by the thief to steal the defender’s property may still constitute an indirect threat to the life of the defender. The thief might still turn his or her force against the defender, and it is this threat to the defender’s life that justifies the defender’s response. Yet not all instances of theft, or even all instances of robbery, entail a real or serious threat to the defender’s life.28 This is a matter of case-by-case evaluation. Thus, given that Locke’s justification for the use of force is the threat to life and limb and not the threat to property, it cannot constitute a general rule for the use of force in defence of property. Grotius holds that force may be used in defence of property only when the life of the defender is endangered either by the thief or by the loss of property. However, this right extends to those situations in which the defender comes into danger trying to defend or recover his or her goods. That is because the defender has a right to try and recover his or her property.

Most contemporary scholars ignore the possibility of self-defence to protect property, probably because they concentrate on the use of lethal force, which would be prohibited as disproportionate to the potential harm to property. Rodin finds the use of force in defence of property upon which one’s life directly depends permitted, such as when a thief steals all the water from a person travelling in the desert. That is, in such cases, killing the thief in self-defence is proportionate and thus permissible. Following Grotius, Rodin bases the permission to kill in such cases on the threat to life rather than to property. In all other instances, where there is no threat to life, Rodin argues, the defender is prohibited from using lethal force in defence of property. The reason is that there are established and effective post facto means of redress following attacks on property, whereas such means are obviously not available after an attack on a person’s life.29 However, as already mentioned, Rodin’s discussion is limited to the use of lethal force and does not address the prospect of self-defence of property.

However, in my view, self-defence ought to be permitted in defence of property, provided it fulfils the standard requirements of necessity, imminence and proportionality.30 This would mean, among other things, that: (a) proportionate power may be used only to stop an imminent threat to property and not in an attempt to stop a retreating empty-handed thief; and (b) force may be used only if there is no other way ex ante to protect the property. It should be stressed that, on this view, under no circumstances would killing be a proportionate use of force in defence of property, unless the loss of property generates a direct threat to life. It is noted that the practical application of this principle raises some difficulties, but the discussion of these must be postponed to another time. Here, it is enough to note that this position is accepted today in England and other jurisdictions, and there are jurisdictions that permit even killing in defence of property.31 Similarly, jurisdictions in which self-defence is justified by the theory of a vindication of autonomy (eg, Germany) hold that the right of self-defence extends to protect against the unjustified violation of a defender’s rights, including his or her right to property.32


The following discussion of the connection between the individual right of self-defence and the state’s duty to defend its citizens will involve reference to the individual right of self-defence against threats to life, property and liberty, and to a state’s duty to defend its citizens against threats to life and liberty. The distinction between the various types of threats that trigger the individual right and the state’s duty are of great importance. The individual right of self-defence against threats to life will be called the core-right of self defence, and possible extensions of the individual’s right of self-defence to protect against threats to property or to liberty will be called property-extended and liberty-extended rights respectively, or generally, the extended right of self-defence. Subsequently, the state duty to defend its citizens against threats to life will be called core-duty, and possible extensions of the duty to include defence against threats to liberty will be called liberty-extended duty or extended duty.

The best way to explain the connection between the individual right of self-defence and the state’s special duty to defend its citizens is either (a) as the duty corresponding to the individual core-right against threats to life, or (b) as derivative from the individual’s core-right to self-defence. Both explanations limit the state’s duty to the conditions established for the proper exercise of the individual’s core-right. A right cannot generate a corresponding duty that requires another person to act beyond the boundaries set by the conditions under which exercise of the right is permissible. If A has a right to X and not to Y, it means that others have a duty to act either in a way that at the very least does not interfere with A’s actions with regard to X, or in a way that actively helps A to obtain X. But A’s right to X cannot generate a duty in others to act in a way that does not interfere with or promotes Y. Similarly, a derivative right or duty cannot extend beyond the scope of the right from which it derives.

Nevertheless, I propose that the state has a special extended duty to respond not only to threats to life but also to severe threats to liberty. One way to establish this connection is to argue that the individual core-right of self-defence generates a special core-duty of self-defence against threats to life or serious physical injury, which is owed by the state to its citizens. The extension of the state’s duty to respond also to threats to liberty would then be justified by analogy to the state’s duty against threats to life. The need for an analogy-based justification rests on the fact that the core-right of self-defence cannot directly create a wider derivative duty. However, as shall be seen, this analogy-based justification is bound to fail. The failure is nevertheless illuminating and aids understanding of the connection between the individual right of self-defence and the state’s extended duty to defend its citizens.

This account of the state’s liberty-extended duty involves two stages: first, it is necessary to establish that the individual core-right to self-defence generates the corresponding state duty of self-defence against threats to the life of its citizens; and subsequently, it is necessary to justify by analogy the extension of the state’s core duty of self-defence to include the duty to respond to threats to the liberty of its citizens. The argument is that in the realm of the individual, the right to self-defence has been extended by analogy to protect threats to property; and, similarly, we ought to be able to draw on some characteristics of the state’s core duty of self-defence against threats to life in order to extend, by analogy, to the state’s duty to protect against threats to liberty.

This account, however, suffers from a major weakness, namely, that the two stages of the argument for the state’s liberty-extended duty cannot be reconciled. The argument advanced in the second stage is that the individual has only a core-right to self-defence against threats to life, whereas the duty of the state that this right generates extends, by analogy to the core-duty, to include threats to liberty. Yet this argument is unsustainable. According to the analogy-based argument, once we have established that the state has a core duty of self-defence against threats to the lives of its citizens, it is possible to justify the state’s extended duty to defend itself from severe threats to liberty as an analogous duty. This is similar to the claim that the right to self-defence should extend to include defence of property. In the discussion of self-defence of property, the claim that defence of property might be justified by appealing to the right not to be killed was expressly rejected. Instead, it was argued that defence of property per se, even when no threat to life is involved, ought to be recognised provided it is subject to the same conditions of necessity, imminence and proportionality that characterise the core-right to self-defence.

Along these lines, it might seem possible to argue for an extension of the state’s duty of self-defence to include threats to liberty. The problem with this line of reasoning is that there are important differences between the justifications that ground the individual core-right to self-defence and those that ground the state’s core-duty of self-defence. In the individual realm, the core-right to self-defence against threats to life is justified by appealing to a basic right not to be killed, or the right to life. Therefore, it seems legitimate to appeal to a second basic right, that is, the right to property, to ground an analogous derivative right to protect against threats to property.

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