Self-defense is an ancient common law right under which necessary and reasonable force may be used to defend one’s person or property. As Sir Edward Coke expressed it in 1604: “The house of everyone is to him as his Castle and Fortress as well for defense against injury and violence . . . if thieves come to a man’s house to rob him, or murder, and the owner or his servants kill any of the thieves in defense of himself and his house, it is no felony, and he shall lose nothing.”

The meaning of reasonable force has always been heavily context-dependent, considering the facts of the case including the intentions of the parties. If a trial were to become necessary in the scenario described by Coke, the court would have to establish that the intruders were indeed thieves intent on robbery or murder, or at any rate that the homeowner reasonably believed this to be the case. The use of force to defend oneself from an attack inherently carries the risk of causing the attacker’s death, making it necessary to ascertain that this was not merely a homicide masquerading as self-defense. Otherwise, anyone could shoot another and argue that he thought it was an intruder, as happened in the Oscar Pistorius case.

If the attacker shoots first, it is not unreasonable to shoot back. Difficult cases arise where the attacker is unarmed or armed only with the natural weapons of his own fists. The old common law rule, as reported by the Michigan Law Review in 1904, was that

it was not necessary the assault should have been made with a deadly weapon, but that an assault with the fists alone, if there was apparent purpose and ability to inflict death or serious bodily injury, was sufficient to justify the killing in self-defense. . . . a mere battery by the fists alone, will not justify an homicide, even where there is a great disparity of physical power, without a plain manifestation of felonious intent.

The felonious intent of the attacker (intention to inflict death or serious bodily injury) has long been treated as key to justifying killing the attacker, and such intention could only be judged in all the circumstances of the case. Mere words would not suffice, as one might shout, “I’ll kill you!” with neither felonious intent nor ability, and conversely an intention and ability to kill may be exhibited clearly without any words being uttered.

In the context of comparative law, Uwe Steinhoff controversially goes further to argue that self-defense ought to be lawful even if the attacker did not use his fists: “An attack need not involve physical force; rather, an attack is every threat of violation or actual violation of an interest that is protected by law (that is, of a right) insofar as this threat stems from human action.” Steinhoff distinguishes between an “attack” and “harm” as in his view one is still entitled to defend oneself against an attack without waiting to see the degree of harm, if any, that might result from the attack.

Imagine a scenario where a weak and puny man launches himself at a weightlifting champion with intention to cause harm, only for the attacker’s fists to bounce ineffectually off his victim (as happened once to Arnold Schwarzenegger). In Steinhoff’s view, the victim in this case, bigger and stronger than his attacker though he may be, would nevertheless have a right to defend himself with a reasonable degree of force.

The aim of mentioning these examples is not to comment on the current law, which is too heavily circumscribed by legislation and case law to permit brief summary. The aim here is instead to highlight some of the difficulties in ascertaining the boundaries of self-defense. Legislative rules are typically detailed and encompass numerous conditions and exceptions.

For example, in New York, “deadly physical force” generally cannot be used unless

“the actor reasonably believes that such other person [the attacker] is using or about to use deadly physical force. Even in such case, however, the actor may not use deadly physical force if he or she knows that with complete personal safety, to oneself and others he or she may avoid the necessity of so doing by retreating.”

That is easy to state, but in reality, how would one “know that with complete personal safety” violence can be avoided by retreating? In many circumstances where deadly force is used or threatened, there are no guarantees of “complete personal safety.” In Steinhoff’s example, it is rarely clear that there is no other way to save Snow White other than by taking out the evil queen: “Yet one is certainly allowed to tackle the evil queen with physical force in order to prevent her from giving the apple to Snow White if there is no other way to save Snow White.”

It is in practice often difficult (though not impossible) to show that there was no other way to avert the threat other than by use of deadly force, primarily because decisions must often be made in split seconds. The point here is that on a test of reasonableness, it would not suffice simply to say “there was no other way”—it would be necessary to show this to be in fact the case. It is one thing to understand clearly the meaning of self-defense and another to ascertain whether defensive action is justified on the facts of specific cases.

Natural Law and Natural Rights

From a natural law perspective, the right to self-defense is an element of the right to self-ownership. Self-defense entails the right to wield force in defense against any forceful invasion. As Murray Rothbard explains:

If every man has the absolute right to his justly-held property, it then follows that he has the right to keep that property—to defend it by violence against violent invasion . . . for if a man owns property and yet is denied the right to defend it against attack, then it is clear that a very important aspect of that ownership is being denied to him.

That is no more than a starting point, as it is still necessary to ascertain the scope of the right to self-defense. Rothbard asks:

How extensive is a man’s right of self-defense of person and property? The basic answer must be: up to the point at which he begins to infringe on the property rights of someone else. . . . It follows that defensive violence may only be used against an actual or directly threatened invasion of a person’s property—and may not be used against any nonviolent “harm” that may befall a person’s income or property value. (emphasis added)

It is by no means straightforward to decide what “directly threatened invasion” means in specific cases. In Rothbard’s example, where “someone approaches you on the street, whips out a gun, and demands your wallet,” the threat is clear. However, he notes that an invasion or threat of invasion need not be “actual physical aggression” but may include intimidation or even fraud, which is “implicit theft” and thus a threat against one’s property. Rothbard insists however that the threat must be direct, overt, and clear; it must be “palpable, immediate and direct,” not “vague and future.”

Rothbard cautions that “in the inevitable case of fuzzy or unclear actions, we must bend over backwards to require the threat of invasion to be direct and immediate . . . the burden of proof that the aggression has really begun must be on the person who employs defensive violence.” Thus, violence can only be deployed in response to violence: “It would clearly be grotesque and criminally invasive to shoot a man across the street because his angry look seemed to you to portend an invasion,” and the response to a violent threat must be proportionate: “The criminal, or invader, loses his own right to the extent that he has deprived another man of his.” To shoot dead a shoplifter, for example, would be disproportionate: “In fact, the storekeeper has become a far greater criminal than the thief, for he has killed or wounded his victim—a far graver invasion of another’s rights than the original shoplifting.”

It would indeed be grotesque to summarily execute people for shoplifting, but that assumes a simple case where it is clear that the invader is intent only on shoplifting. The case would be different in circumstances where it is impossible to distinguish between a mere shoplifter and an intruder whose intention, as far as can be ascertained under the circumstances, seems reasonably to be to cause grave bodily harm. For example, in the case of Tony Martin, the outcome turned on the fact that the burglars were in the process of fleeing when he shot at them:

Fearon, 29, and 16-year-old Fred had travelled from Newark in Nottinghamshire on the evening of 20 August to raid Bleak House, the semi-derelict farm building in Emneth Hungate, Norfolk . . . Upon hearing them, Martin came down from an upstairs bedroom and opened fire with a pump-action shotgun. Martin claimed to have been acting in self-defence; prosecutors argued he had anticipated the pair and lay in wait for them.

The case would have been different if he had shot them on entry rather than exit. After all, it may not have been clear to him whether the burglars’ intention was merely to burgle or to cause him bodily harm. He could in theory have called out to the intruders, “Halt and state your intentions!” in the manner of a soldier on patrol, but most criminals intent on causing harm are unlikely to yield peacefully to such an inquiry.

In the common law context, these issues are all components of reasonable force. Deadly force used in response to a threat that is neither direct nor immediate but is merely speculative or remote would not count as reasonable.

Peaceful Adjudication of Disputes

To avoid these difficulties, common law jurisdictions have long upheld a strong policy preference for the peaceful settlement of disputes and have constrained as far as possible the deployment of force. In Jacque v. Steenberg Homes, Inc. (1997), the supreme court of Wisconsin observed in a case of trespass that one reason why the state steps in to vindicate violations of property rights is to discourage people from resorting to “self-help” remedies. In this way, courts hope to discourage people from deploying force in defense of their own rights:

In McWilliams, the court recognized the importance of preventing the practice of dueling, by permitting juries to punish insult by exemplary damages. Although dueling is rarely a modern form of self-help, one can easily imagine a frustrated landowner taking the law into his or her own hands when faced with a brazen trespasser.

The policy goal is “the preservation of the peace” or “providing an incentive for plaintiffs to bring petty outrages into court” instead of resolving the dispute by rashly throwing down the gauntlet in a fit of temper. For example, the case in the Michigan Law Review cited earlier involved parents fighting over the aggravating behavior of their children:

On the morning of the murder, the defendants were passing Hallgarth’s premises when he hailed them and a heated conversation ensued over some difficulty about Gray’s children at school. Hallgarth leaping over the fence, but without weapons of any kind except his bare fists, advanced in a threatening manner upon Gray, who thereupon drew his pistol and warned him to desist.

The reasoning behind the legislative regulation of self-defense is to discourage people from leaping over fences and resorting to fisticuffs in disputes with their neighbors. Most jurisdictions also prohibit or strongly discourage self-help in property disputes, especially in the context of tenancies, in favor of calling the authorities to deal with any violation of the owner’s rights:

It would still be necessary to prohibit forms of self-help, such as padlocking, because of the foreseeable and, therefore, unnecessary one-on-one confrontation. . . . It does not take a mystic or a psychologist to see the possibilities for violence and conflict in these scenarios. A lockout attempt, whether done face to face or like a thief in the night when the occupant is away, can be a provocative act. “It is difficult to imagine a more volatile situation from which extreme violence could be reasonably anticipated than the surreptitious removal of a man’s home, whether it be a rented one or a mortgaged one.”

The question libertarians must nevertheless ask is whether the state is justified, in its attempt to keep the peace, in limiting the right to self-defense. Even if we stipulate that the state is a parasite and everything the state does is therefore inherently wrong, it would still be necessary to address the question of how peaceful interaction can be maintained in situations where human beings are wont to fly off the handle and take potshots at each other with or without weapons. Human nature being what it is, this problem would also arise for private defense agencies to which people in a libertarian society had voluntarily subscribed.

To avoid violent conflict in a dispute resolution, it is certainly a good idea to encourage peaceful adjudication. It is however important to reiterate that the right being vindicated through such adjudication is not the right to a fair trial but, according to Rothbard, the right to self-defense:

Presumably, a free market will tend to lead to most people choosing to defend themselves with those private institutions and protection agencies whose procedures will attract the most agreement from people in society. In short, people who will be willing to abide by their decisions as the most practical way of approximating the determination of who, in particular cases, are innocent and who are guilty. But these are matters of utilitarian discovery on the market as to the most efficient means of arriving at self-defense, and do not imply any such fallacious concepts as “procedural rights.”

Agreeing to resolve disputes through arbitration proceedings, for example, or any other institutional form of dispute resolution must therefore not be taken as a reason to undermine the right to self-defense. The right to self-defense rests in the person whose property right is violated and not in society or in the state. Thus, the individual also has a natural right to bear arms as an emanation of the right to self-ownership. As Rothbard explains: “Every man has the absolute right to bear arms—whether for self-defense or any other licit purpose.”

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This article was published by the Ludwig von Mises Institute and is reproduced with permission.