Throughout history, whenever states and/or peoples have taken up arms, they have asserted that they were doing so for a just cause. All too often this argument has been used to justify refusing their opponents any mercy. In fact, history shows that the more the belligerents insist on the sanctity of their reasons for resorting to armed force, the more those same reasons are used to justify the worst excesses. The crusades and the wars of religion, alas, left a long trial of atrocities in their wake.
It was only when war was recognized as a very imperfect means of settling a dispute between two sovereigns that states began to accept the idea of limiting armed violence. The emergence of nation states and the development of professional armies led states to gradually accept a body of rules intended to limit the horrors of war and to protect its victims. For a long time, these rules remained customary in nature; they began to be codified in the mid-Nineteenth Century.
International Humanitarian Law developed at a time when the use of force was a lawful form of international relations, when states were not prohibited to wage war, when they had the right to make war, meaning, when they had the Jus ad bellum. There was no logical problem for international law to prescribe them the respect of certain rules of behavior in war called the jus in
Today the use of force between states is prohibited by a peremptory rule of international law. This has made the jus ad bellum to change into a jus contra bellum. Exceptions to this prohibition are admitted in case of individual and collective self-defense, Security Council enforcement measures, and arguably to enforce the right of peoples to self-determination or national liberation wars. Logically, at least one side of an international armed conflict is, therefore, violating international law by the sole fact of using force, however respectful of IHL. All municipal laws of the world equally prohibit the use of force against governmental law enforcement agencies in the case of non-international armed conflict.
Although armed conflicts are prohibited, they happen, and it is today recognized that international law has to address this reality of international life not only by combating the phenomenon, but also by regulating it to ensure a minimum of humanity in this inhumane and illegal situation. However, for practical, policy, and humanitarian reasons, international humanitarian law has to be the same for both belligerents: the one resorting lawfully to force and the one resorting unlawfully to force. From a practical point of view, the respect of international humanitarian law could otherwise not be obtained, as, at least between the belligerents, it is always controversial as to which belligerent is resorting to force in conformity with the jus ad bellum and which violates the jus contra bellum. In addition, from a humanitarian point of view, the victims of the conflict on both sides need the same protection, and they are not necessarily responsible for the violation of the jus ad bellum committed by “their” party.
International Humanitarian Law has, therefore, to be respected independently of any argument of jus ad bellum and has to be completely distinguished from jus ad bellum. Any past, present, and future theory of just war only concern jus ad bellum and cannot justify that those fighting a just war have more rights or less obligations under international humanitarian law than those fighting an unjust war.
This complete separation between jus ad bellum and jus in
“The High Contracting Parties,
Proclaiming their earnest wish to see peace prevail among
peoples, Recalling that every state has the duty, in conformity with the charter of the United Nations, to refrain in its international relations from the threat or use of force against the sovereignty, territorial integrity or political independence of any state or in any other manner inconsistent with the purposes of the United Nations
Believing it necessary nevertheless to reaffirm and develop the provisions protecting the victims of armed conflicts and to supplement measures intended to reinforce their application,
Expressing their conviction that nothing in this protocol or in the Geneva Conventions of 12 August 1949 can be construed as legitimizing or authorizing any act of aggression or any other use of force inconsistent with the charter of the United Nations,
Reaffirming further that the provisions of the Geneva Conventions of 12 August 1949 and of this protocol must be fully applied in all circumstances to all persons who are protected by those instruments without any adverse distinction based on the nature or origin of the armed conflict or on the causes espoused by or attributed to the parties to the conflict. (...)”
This complete separation between jus ad bellum and jus in
There are also some writers who do not confine themselves to just showing the distinction between jus ad bellum and jus in
That being the case, the following question arises: Is the fact that a belligerent has resorted to armed force in violation of international treaties and commitments an obstacle to the application of jus in
I) Either the war of aggression is deemed to be the international crime par excellence, a crime which subsumes all others and which therefore cannot be regulated, in which case the laws and customs of war do not apply to either of the belligerents; or
II) The aggressor alone is deprived of the rights conferred by jus in
The first hypothesis is only one that draws all the logical conclusions from any subordination of jus in
The second solution entails a differentiated application of the laws and customs of war, but it must be rejected just as vigorously as the first, for in practice it would produce the same result. In the absence of a mechanism to determine aggression and to designate the aggressor in every case and in such a way as to be binding equally all belligerents, each of the latter would claim to be the victim of aggression and take advantage of this to deny his adversary the benefits afforded by the laws and customs of war. In practice, therefore, this solution would lead to the same result as the hypothesis whereby wars of aggression cannot be regulated: a surge of unchecked violence. The autonomy of jus in
War cannot be just on both sides: One party claims a right, the other disputes the justice of the claim; one complains of an injury, the other denies having done it. When two persons dispute over the truth of a proposition it is impossible that the two contrary opinions should be at the same time true. However, it can happen that the contending parties are both in good faith; and in a doubtful cause it is, moreover, uncertain which side is in the right. Since, therefore, Nations are equal and independent, and can not set themselves up as judges over one another, it follows that in all cases open to doubt the war carried on by both parties must be regarded as equally lawful, at least as regards its exterior effects and until the cause is decided.
Thus, Vattel does not expressly reject the doctrine of just war, developed by the fathers of the Church, but puts it into perspective and draws its sting.
The autonomy of jus in
The Geneva Conventions of 12 August 1949 doubly confirmed the autonomy of jus ad bellum. First, in Article 1 common to the four Conventions, the High Contracting parties undertake to respect and ensure respect for these instruments ‘in all circumstance.’ There can be no doubt that in adopting this provision states ruled out the possibility of invoking arguments based on the legality of the use of force in order to be released from their obligations under the Conventions.
Secondly, the Conventions prohibit any reprisals against persons or property protected by their provisions. Obviously, any state using the argument that it is the victim of a war of aggression to justify its refusal to apply humanitarian law to enemy nationals would be in violation of this prohibition.
Finally, the preamble to Protocol I additional to the Geneva Conventions, adopted by consensus on 7 June 1977, put an end to all argument on the matter by a pointing out that:
... The provisions of the Geneva Conventions of 12 August 1949 and of this protocol must be fully applied in all circumstances to all persons who are protected by those instruments, without any adverse distinction based on the nature or origin of the armed conflict or on the causes espoused by or attributed to the Parties to the conflict.
The principle of the equality of belligerents before the law of war, which is in a way the corollary of the autonomy of jus in
This principle dominates the entire body of the laws and customs of war. It finds its main application, however, in the status of prisoners of war as it took shape in
If the application of the principle of the equality of belligerents before the law of war raises major difficulties in situations of international armed conflict, it may well be imagined that even more formidable obstacles lie in its way in situations of non-international armed conflict. Indeed, a state facing an insurrection will almost invariably begin by invoking a dual inequality: On the one hand, the state will accuse the insurgents of having violated national law and endeavour to bring the full force of the criminal law to bear against them; while claiming to be fully within its rights, it will do everything it can to criminalize its adversaries; On the other hand, the state will rely on the inequality of the insurgents’ legal status under domestic law and, in most cases, under international law, to justify rejecting any relationship with them based on an equal footing.
This clearly indicates the case where by the autonomy of jus in