The various types of hostile conduct which have just been described, although outwardly dissimilar, actually share a common characteristic—that of disregard for or deliberate non-compliance with the qualifications established for an individual’s recognition as a prisoner of war upon capture. In a sense all of them also constitute ruses of one sort or another, if by ruse is understood any means of deceiving the enemy. Since these qualities are those which most conspicuously inhere in espionage, resistance activities in occupied areas, guerrilla warfare, and private hostilities in arms, they afford grounds for believing that all these acts of warfare, whether or not involving the use of arms and whether performed by military persons or by civilians, are governed by a single legal principle. That this larger category of hostile conduct is not violative of any positive prohibition of international law is demonstrable by much the same considerations as militate against an internationally imposed duty of obedience to the belligerent occupant. In both occupied and unoccupied areas, resistance activities, guerrilla warfare, and sabotage by private persons may be expected to continue on at least as widespread a basis in future warfare as they have in the past. More often than not, patriotism or some sort of political allegiance lies at the root ofsuch activities. Consequently the law ofnations has not ventured to require of states that they prevent the belligerent activities of their citizenry or that they refrain from the use of secret agents or that these activities upon the part of their military forces or civilian population be punished. Evidence of the unwillingness of international law to intervene in such matters is found in the failure of those who have compiled lists of ‘war crimes’ for which persons are actually to be tried to include such acts as espionage or guerrilla fighting. The weight of precedent and history represented by the law applicable to espionage and the importance for practical purposes of the law relating to the hostile conduct of occupied populations together suggest that the supposed illegality of those other types of secret warfare which have been mentioned is based upon a misconception. The correct legal formulation is, it is submitted, that armed and unarmed hostilities, wherever occurring, committed by persons other than those entitled to be treated as prisoners of war or peaceful civilians merely deprive such individuals of a protection they might otherwise enjoy under international law and place them virtually at the power of the enemy. ‘Unlawful belligerency’ is actually ‘unprivileged belligerency’.
International law deliberately neglects to protect unprivileged belligerents because of the danger their acts present to their opponent. The peril to the enemy inherent in attempts to obtain secret information or to sabotage his facilities and in attacks by persons whom he often cannot distinguish from the peaceful population is sufficient to require the recognition of wide retaliatory powers. As a rough-and- ready way of distinguishing open warfare and dangerous dissimulation, the character of the clothing worn by the accused has assumed major importance. The soldier in uniform or the member of the volunteer corps with his distinctive sign have a protected status upon capture, whilst other belligerents not so identified do not benefit from any comprehensive scheme of protection. An exception must, of course, be made of the levee en masse, which cannot be reconciled on principle with the distinction otherwise made between privileged and unprivileged belligerents. There is considerable justice in the contention that to make the difference between life and death hang on the type of clothes worn by the individual is to create a ‘clothes philosophy’ of a particularly dangerous character. Indeed, the emphasis on the properly uniformed belligerent may be only a survival from the type of war fought by closely grouped ranks of soldiers, in which firing upon even individual detached soldiers was regarded as violative of international law. As the current tendency of the law of war appears to be to extend the protection of prisoner- of-war status to an ever-increasing group, it is possible to envisage a day when the law will be so retailored as to place all belligerents, however garbed, in a protected status.
The judicial determination which is necessary before a person may be treated as an unprivileged belligerent is in consequence not a determination of guilt but of status only and, for the purposes of international law, it is sufficient to ascertain whether the conduct of the individual has been such as to deny him the status of the prisoner or of the peaceful civilian. There is actually no need for the creation of separate categories ofoffences, since the person bent on espionage will be subject to the same maximum penalty as the individual who transmits information innocently acquired or who engages in secret warfare. The fact that a given individual will, as a matter of practice, carry on a variety of forms of hostile conduct is a further reason why international law need not work out any code of ‘offences’. What is thereafter to be done to the individual who is found to lack a privileged status is left to the discretion of the belligerent. It may either, as a belligerent act, cause the execution of the offender or it may require the application of domestic law to determine something denominated in that municipal law as ‘guilt’—but a guilt only in the sense of municipal law. In the case of occupied territory Articles 64, 65, and 67 of the Geneva Civilians Convention of 1949 impose a positive requirement that persons in occupied areas be tried only under a municipal law enacted for or applied to the occupied area, and the Convention as a whole so severely restricts the power of the occupant to deal freely with unprivileged belligerency that the resistance worker or guerrilla in occupied territory is actually in a more favourable position than if he had been arrested or captured elsewhere.
A denial that unprivileged belligerency is a violation of international law does not, it must be emphasized, leave the opposing state powerless. Guerrilla warfare may still be met with open warfare and saboteurs and spies captured within the lines may still be penalized, but not for any violation of international law. Except to the extent to which the power to impose the death penalty has been removed by the Geneva Civilians Convention of 1949, the offended state may employ that measure in dealing with clandestine hostile conduct. Moreover, the capturing state is not precluded from punishing an unprivileged belligerent for a war crime stricti juris, if he has, for example, killed civilians, or pillaged or refused to give quarter. Although it may be foreseen that in time of war bandits who live by pillage may attempt to contend that they are guerrillas fighting for the defence of their country, the degree to which they comply with the law of war generally applicable to the armed forces will afford the best indication of their purpose, and particularly of their adhesion to one of the belligerents in the conflict rather than to motives of private gain.
As has already been observed, ‘unprivileged belligerency’ partakes strongly of the nature of a ruse by reason of its clandestine character. The same ‘statute of limitations’ which forbids the punishment by the enemy of a spy who has returned to his own lines accordingly could be applied to other forms of unprivileged belligerency, and there would appear to be strong reasons of policy for doing so. However, although it is easy to determine that a spy’s mission is completed with his return to his own lines, to fix with certainty when the status of ‘unprivileged belligerency’ in other forms is at an end is extremely difficult. Nevertheless, the principle to be applied would appear to be that if an individual has either returned to his own lines or become part of the regular armed forces or has otherwise indicated the termination of his belligerent status, as by long abstention therefrom, he may not be prosecuted by the opposing state for his previous acts ofunprivileged belligerency. In the case of guerrilla warfare or of resistance activities in occupied territory, the cessation of belligerent activity will in all probability be difficult to prove in practice. Furthermore, as the penalizing of the unprivileged belligerent is actually a belligerent act, there is no reason for such action after the definite cessation of hostilities, subject to the exception that new acts occurring thereafter would be punishable on the basis that they had constituted a resumption of hostilities.
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-  Article 69, General Orders No. 100, 24 April 1863, prepared by Dr. Francis Lieber for thegovernment of United States forces in the field, stated: ‘Outposts, sentinels, or pickets are not to befired upon, except to drive them in, or when a positive order, special or general, has been issued to thateffect.’ It is perhaps this distaste for the killing of the detached soldier which accounts for theprohibition of assassination in customary international law. Although this rule is considered to havebeen incorporated into Article 23 (b) of the Hague Regulations, which forbids treacherous killing(Field Manual 27—10, Rules of Land Warfare (1940), par. 31), practice must be considered to havegiven a restrictive interpretation to ‘assassination’, at least to the extent of not rendering internationallycriminal the deliberate killing of individual enemies in battle or in occupied areas. It is, for example,questionable whether the killing of Heydrich in 1942 by three Czech nationals who had parachutedinto Czechoslovakia (see Spaight, AirPower and WarRights (3rd ed., 1947), p. 305) could be said to bean international crime. Butcf. Opinions of the Attorneys General of the United States, 11 (1869), p. 297,dealing with the assassination of President Lincoln.
-  See Gutteridge, ‘The Protection of Civilians in Occupied Territory’, in Year Book of WorldAffairs (1951), p. 290.
-  Article 68.
-  It was at one time suggested that the war traitor who had returned to his own lines shouldbenefit from the immunity extended to the spy (Article 104, General Orders No. 100, 24 April 1863),but the contrary view now appears to prevail (Manual of Military Law (1929), Amendments No. 12 (1936), p. 38; Field Manual 27—10, Rules of Land Warfare (1940), par. 213).