assassination and philosophy of just war

Since the beginning of history, philosophers have recognized exceptions to rules against taking human life, realizing that in certain circumstances an inflexible rule against the taking of life is untenable and unjust. Early legal codes followed the doctrine of nullem crimen sine poena (“no crime without a punishment”), some examples would be the code of Ur Nammu (c. 2100 B.C.E.), the laws of Eshnunna (c. 2000 B.C.E.), and the Code of Hammurabi (c. 1728-1686 B.C.E.). Lex talionis (“exact retaliation”) is a similar doctrine which can be found in three biblical passages, Exodus 21:24, Leviticus 24:20, and Deutoronomy 19:21. These concepts echo the claim that are certain circumstances where violent reprisals are appropriate in order to protect the public, dissuade future offenders, and to achieve justice.
According to St. Thomas Aquinas, “the first precept of law is that good is to be done and pursued and evil is to be avoided.” St. Thomas Aquinas supported violence against a sovereign who was evil in order to spare innocent lives and punish the individuals who act to cause wars. Aquinas did not recognize a difference between a criminal harming a single victim, and a head of state acting in a tyrannical manner harming every individual living under their authority. Aquinas equated both actions without regard to scale, and he believed that a tyrannical ruler should face the same punishment as an individual that commits a similar crime on a smaller scale. Aquinas was centuries ahead of his time in this regard, laying the philosophical framework for the evaluation of all leaders based upon the legality of their actions, and not giving them free reign and absolving them of responsibility simply because of their status as head of state.
Sir Thomas More takes Aquinas a step further, and in his description of his maximally rational society in Utopia, the first move of the Utopians in any war is to offer a large reward for anyone in the enemy territory who kills a member of the enemy leadership, or double that amount if the leaders are kidnapped and brought to the Utopians alive. More recognized that this policy is at odds with the “irrational law of nations,” but praised the utopians for their prudence, humanity, and compassion. More praised their rationality because these “treacherous” acts brought wars to a conclusion without the waging of battles and “for the price of a few harmful lives they purchase[d] numerous harmless lives.” The Utopians realized that the populace of a nation would typically not be responsible for starting a war themselves, that it is the decision of a few that force the populace to war, and so the Utopians attempt to harm the innocent populace as little as possible while focusing punishment on the guilty—the ruling class which instigated the war.
The first appearance of the treachery-perfidy distinction arose in the work of Balthazar Ayala, who shared the philosophy of St. Augustine, that it was “indifferent from the standpoint of justice whether trickery be used” against an enemy, regardless of their political station. However, Ayala did distinguish between trickery and “fraud and snares,” a distinction which survives in today’s legal codes as the perfidy restriction. Ayala began to recognize that the use of perfidious means of attack runs the danger of making a just cause indistinguishable from the actions of the tyrants they resisted.
Alberico Gentili rejected the philosophy of St. Augustine; however he did further develop the perfidy concept begun in the work of Ayala. Gentili rejected the idea of a treacherous or perfidious attack because of the high probability of chaos resulting from the deaths of the leaders of both sides. Gentili considered three possible methods of taking the life of a sovereign: incitement of the subjects to kill a sovereign, a treacherous attack, or an open attack against an unarmed enemy, and he determined that all three possible methods were untenable and impermissible under natural law. Gentili argued that any secretive or treacherous acts should be illegal, because once “you allow murder, there are no methods and no forms of it which you can exclude; therefore murder should never be permitted.” Gentili defined victory through justice and honor, and expressly denied that the killing of a single leader would save many other lives, in fact he believed that a new leader would emerge and the enemy would be enraged and motivated by the method of the former leader’s death. Gentili’s contribution to the philosophical framework underlying the legitimacy of assassination is the addition of the test for unlawful murder, which focuses on the use of treachery in accomplishing the elimination of the target. Further, Gentili would not only hold the actual killer liable for the death of the target, but also those encouraging or financing the activities of the killer.
Grotius specifically considered the issue of whether assassination could be a legitimate method to kill an enemy, and he expressly distinguished between those with a good faith obligation to support a leader, and those with no such obligations. Those with good faith obligations, such as subjects of a king, soldiers and their superiors, and even strangers and those giving them shelter or aid could not lawfully kill those with whom they have such an obligation. However, those without such obligations are free to kill an enemy wherever they encounter them so long as they do not use treacherous means or offer a reward for the death of an enemy. Grotius saw no illegality in the action of Pepin, who is reported to have crossed the Rhine River at night, snuck into an enemy encampment, and killed the sleeping commander. A fascinating part of Grotius’s philosophy is his stance on treachery used against enemies of all states, such as “robbers and pirates,” who he claims is not morally correct, but is at least accepted by the international community “by reason of hatred of those against whom it is practiced.”
According to Emmerich de Vattal, assassination is “a murder committed by means of treachery,” and condemned the use of such tactics in warfare. Vattel’s major contribution to the philosophy of the laws of war relating to assassination is the emphasis on necessity. The circumstances where Vattel approves of the targeting of leaders are extreme, as “to take away the life of the enemy's sovereign, when it might be spared, is perhaps doing that nation a greater degree of harm than is necessary for bringing the contest to a happy issue.” Vattal only approves of the targeting of regime leaders when the harm done to that leader’s own state is not greater than the harm needed to be inflicted to subjugate that particular enemy otherwise, but the law does not require that the person of the regime leader be spared because of their position. Vattal stated in The Law of Nations, that “[m]en who are by profession poisoners, assassins or incendiaries may be exterminated wherever they are caught for they direct their disastrous attacks against all Nations, by destroying the foundations of their common safety.”
A view of war more in line with our modern conception of total war is represented in the legal philosophy of Bynkershoek. According to Bynkershoek, “war justifies every method of destroying the enemy.” Bynkershoek justifies this approach by arguing that the welfare of one’s own people and state rises above the concern for how that welfare is protected or accomplished. The use of assassins is specifically mentioned as a legitimate tactic to destroy an enemy. There is only one restriction on this provision of virtually unlimited action, which is the banning of the use of perfidy. Perfidy, for Bynkershoek, was defined as the breaking of an agreement, which was unacceptable to him because when an agreement has been made the relationship between opponents has been altered, and in the realm covered by that agreement, because when an agreement “has been made the enemy ceases to be an enemy as far as regards the [agreement].”
Kant described a state of nature that was more dangerous than even that of Thomas Hobbes, in order to demonstrate the necessity of international federalism to protect the community of nations. Interaction between states, including war, must be carried out so as not to preclude future lawful interactions among those states. As a result, Kant specifically outlaws assassination as a legal means of acting on the international stage, even in a time of hostilities. A state which uses assassination as a tactic against its enemies will have destroyed the mutual confidence between states which must exist to enact a subsequent peace and international order, and as a result, Kant believes that assassination is an unlawful tactic.