Exceptions to the Separation Between the Jus ad Bellum and Jus in Bello
According to canonic learning and overwhelming practice, the rules of the jus ad bellum and those of the jus in bello are separated in the sense that the application of each depends on its own legal triggers and regulations. This principle of separation works both ways.
The independence of the jus in bello from the jus ad bellum means that the existence or absence of legal authority to use force has no impact on the legal rules to be applied during the conflict. In short, the “aggressor” and the “aggressed” apply the same rules under the jus in bello; the discrimination against the aggressor remains confined to the jus ad bellum and the law of peace (sanctions). For humanitarian and other reasons, the principle applicable in this context is therefore one of “equality of belligerents” in the application of the law of armed conflict.
This principle of equality does not, however, apply in absolute terms. It refers to customary international law and to the conventions and treaties applicable between the belligerents. The application of the latter depends on their status of ratification, accession, and entry into force. Therefore, the belligerents do not necessarily apply the same rules in each armed conflict.
Because of the operation of reciprocity, such equality is always assured in cases involving only two belligerents. They will apply their common rules: those of general international law and those under the applicable conventions and bilateral agreements. In an armed conflict with more than two belligerents, general international law rules form the common ground of the applicable law, whereas the law specific to the belligerents splits according to the bilaterally applicable treaties. The fact that the same rules no longer apply to all parties in such situations is made clear when considering the unambivalent rejection of the si omnes clause (general participation clause) in Common Article 2(3) of the Geneva Conventions of 1949:
Although one of the Powers in conflict may not be a party to the present Convention, the Powers who are parties thereto shall remain bound by it in their mutual relations. They shall furthermore be bound by the Convention in relation to the said Power, if the latter accepts and applies the provisions thereof.
Conversely, the independence of the jus ad bellum from the jus in bello means that the proper application of jus in bello rules does not provide a State with powers and entitlements under the jus ad bellum. The entitlement to use force is regulated only by the jus ad bellum, with its three generally accepted exceptions: authorization by the Security Council under Chapter VII of the UN Charter; self-defense under Article 51 of the UN Charter and customary international law; and intervention by invitation of the government of the territorial State under customary international law.
There are, however, exceptions to this canonic separation. These exceptions are concentrated in areas where the humanitarian concerns are less acute, or the titles to use force are not jeopardized. In such circumstances, one may observe instances of “contamination” of the jus ad bellum by the jus in bello (or vice-versa) under the pressure of evolutions of international society, needs felt in the context of new warfare or new international institutions, equitable considerations, and the like. By canvassing practice and legal writings, one can see four main categories of contamination. The purpose of this post is to present the main categories and discuss the context in which such legal cross-contamination occurs.
Reshaping of an Area of the Law by Placing it Under the Influence of Another
This is certainly the most radical category: an area of the law, belonging to one branch of law, is reshaped by the influence of another. The most striking example is the law of neutrality. Another would be the evolution of blockade law through the law of maritime interdictions decided by the UN Security Council.
To focus on neutrality, traditionally, this was a subset of the jus in bello. It concerned the relations of the belligerent States with those States not participating in the armed conflict. With the advent of collective security systems such as the League of Nations and later the UN, international legal practice shifted to make the old law of neutrality compatible with the new systems. It has thus been held that the old law based on “strict” neutrality under the jus in bello could not be upheld in the modern world to the extent it was incompatible with the new collective security systems under the jus ad bellum. Thus, either neutrality had to become obsolete or it had to become differential, i.e. to accommodate the measures taken under collective security against the “aggressor” (so-called “differential neutrality”).
Because neither the Covenant of the League of Nations nor the UN Charter contains rules obliging a State to participate in coercive armed action against the State targeted by collective security measures, an obligation which would indeed have been in sharp contrast with neutrality, the extent of the “differential” neutrality has remained to some extent unclear. The nodal point was the extent to which a neutral would have to treat the belligerents unequally with regard to sanctions meted out by the relevant organization. For a time, there was the understanding of some general principle of equality of treatment under the law of neutrality; a feeling that held Switzerland aloof from the UN until 2002. This principle was often taken from the Preamble of the Hague Convention (XIII) concerning the Rights and Duties of Neutral Powers in Naval War (1907), which states the following general rule: “Seeing that it is desirable that the Powers should issue detailed enactments to regulate the results of the attitude of neutrality when adopted by them; Seeing that it is, for neutral powers, an admitted duty to apply these rules impartially to several belligerents.”
However, as I have noted elsewhere, this principle of equality of treatment applies only to special areas of neutrality and has no overarching value. The laws to which the preamble refers are those regulating the attitude of the neutral State regarding the treatment of belligerents in areas relevant to neutrality, namely on war-sustaining action of an indirect nature, such as the granting of credits which could serve to purchase weapons, etc. It stands to reason that these rules of municipal law must be applied equally to both belligerents, in the sense that the duty to abstain from war-sustaining action is of an absolute nature. A neutral cannot claim that it has granted credits to both belligerents, and that by thus satisfying the principle of equality, it has respected its duties; it must equally abstain from granting such credits in the first place. In short, this principle of equality is inherent in the overarching principle of (equal) abstention.
With regard to the extent to which a neutral State could follow the sanctions meted out by the League of Nations or the UN without impinging on its duties of neutrality, it was increasingly accepted that the duties under collective security prevailed and that the principle of “equality of treatment” would be erased to the extent it opposed the carrying out of the collectively decided sanctions. This course was qualified as “differential neutrality.” In a more modern version, followed by Switzerland since 1993, the law of neutrality is not applicable to measures taken by the UN. If that course is followed, there are simply no neutrality duties in that area and therefore there is also no “differential neutrality.” The law of collective security and the law of neutrality would have entirely separate spheres of application.
Be that as it may, the result of these evolutions is that the law of neutrality, belonging anciently only to the jus in bello is now a mixture of jus in bello and jus ad bellum. The jus in bello regulates the traditional duties of abstention, action, and acceptance of certain belligerent rights (such as visit and search of ships), and the jus ad bellum limits or pushes back neutrality with regard to all collective security measures decided by the UN or regional security systems (for the parties to that systems). The result is a reshaping of an area of the jus in bello by the not very benevolent incursion of the jus ad bellum.
Cross-Relation in the Trigger for Application of the Law
A second example shows that the conditions or triggers for the application of rules in one area of the law may depend on another area. A good example is the law regulating belligerent occupation. The triggering elements are regulated at first sight by the jus in bello alone, under Article 42 of the Hague Regulations of 1907: “Territory is considered occupied when it is actually placed under the authority of the hostile army” (emphasis added). There is thus a requirement that the occupation be hostile.
This element is interpreted under the jus in bello as signifying that there is no consent to the occupation by the legitimate sovereign of the territory at stake. Whether that is the case, however, will depend on jus ad bellum rules, to which Article 42 may be understood to refer (under a current interpretation, not a historical one, because the relevant jus ad bellum rules did not exist in 1907). If the occupation takes place under action not covered by the jus ad bellum (e.g. aggression, but also humanitarian intervention or the like), or if it takes place under an authorization of the UN Security Council or self-defense, the territory that has fallen under the control of the advancing army will be occupied in the sense of jus in bello. If, conversely, there is an invitation by the recognized government of the territory, the presence will be consensual and there will be no belligerent occupation (at most only pacific occupation, to which rules of the stationing agreements will apply).
Consider for example the presence of France in Mali from 2013 to 2022. While the formal trigger for the application of the law of belligerent occupation remains one of the jus in bello, incorporated in the Hague Regulations, materially this trigger will turn on jus ad bellum classifications. It is clear that the jus in bello is here “contaminated” by the jus ad bellum, and that even the protection of civilians within occupied territories will depend on a jus ad bellum consideration. This is a quite massive incursion of the jus ad bellum into the jus in bello. It rests on the very definition of belligerent occupation, which must be “hostile.”
Expansion of the Ability to Act
Article 52(2) of Additional Protocol I (AP I) to the Geneva Conventions (1977) defines, for the purposes of the jus in bello, which targets may be attacked (military objectives) and thus conversely, which persons and objects must not be subjected to attacks. The definition is quite constraining: an object cannot be made the object of attack when it makes no contribution to military action and where there is no military advantage flowing from the attack. There is some quibbling on the precise meaning of “military” in the provision mentioned, to determine whether it encompasses only “military operations” (mainstream) or includes all “war-sustaining action” (United States, Israel). But this issue of interpretation is not critical to the analysis at hand.
The question has arisen whether a belligerent can attack a concentration camp to curb the extermination of people occurring there. This point was discussed in relation to Auschwitz, which U.S. forces had not bombarded during the Second World War, and it has resurfaced regularly since then. Under Article 52(2) of AP I, the attack is not allowed, under either of the two interpretations mentioned above. A concentration camp makes no contribution to military action, nor does it sustain the war effort; it operates alongside the armed conflict and is concerned with the extermination of populations of certain people.
There may be even an additional bulwark against the extension of attacks to other objects, through the rules of non-derogation contained in Articles 6/6/6/7 of the Geneva Conventions (GC) of 1949. In the text taken from the First Geneva Convention (GC I):
In addition to the agreements expressly provided for in Articles 10, 15, 23, 28, 31, 36, 37 and 52, the High Contracting Parties may conclude other special agreements for all matters concerning which they may deem it suitable to make separate provision. No special agreement shall adversely affect the situation of the wounded and sick, of members of the medical personnel or of chaplains, as defined by the present Convention, nor restrict the rights which it confers upon them.
Allowing objects that are not military objectives in the sense of Article 52(2) to be attacked normally worsens the position of the protected persons. In other words, it “adversely affects” them. As a matter of principle, the general rules of the GCs apply to their Protocols. However, it could be argued that the civilians protected under GC IV are not the same as those protected under AP I in the section “Protection of the civilian population” because under GC IV, the civilians protected are those in the hands of the enemy outside hostilities, whereas those covered by AP I are the civilians suffering the effects of hostilities. If such an interpretation is followed, Articles 6/6/6/7 of the GCs would not apply in our context.
Does this jus in bello regulation limit the powers of the UN Security Council under UN Charter law? Could the Security Council decide to authorize UN member States to attack such a concentration camp to curb or terminate the genocidal or quasi-genocidal activities taking place there? It does indeed not seem that the jus in bello “contaminates” the jus ad bellum here, i.e. that Article 52(2) AP I binds the Security Council not to designate any other object for attack. There may be jus ad bellum reasons to command an attack on certain objects, such as the need to halt the serious international crimes being committed there, independently of all warfare considerations.
To limit the powers of the Security Council in its Chapter VII actions, there would have to be some express provision to that effect. This is not the case here: Article 52(2) AP I concerns the conduct of the armed conflict, not the enforcement of other interests by the Council. It could also be recalled that this provision is not strictly exhaustive within the body of the jus in bello. Indeed, there are lex specialis exceptions, so to speak intra legem. Thus, pursuant to Article 23(g) of the Hague Regulations, private property may be destroyed when “imperatively demanded by the necessities of war.” This criterion is larger than the one of military contribution/advantage under Article 52(2) AP I. Thus, an object making no military contribution at all, such as a civilian house, could be destroyed by an attack if it hinders the passage of military vehicles during an armed confrontation.
Overall, it can thus be said that the jus ad bellum offers a belligerent the possibility to attack some objects that are not covered by Article 52(2) AP I under UN Charter law. Its ability to act is extended beyond what is permitted by the jus in bello.
Interpretation or Cumulative Analysis
The final category concerns cross-fertilization or taking into mutual consideration (in the context of interpretation or integrated legal analysis) all relevant factors. An initial example is provided by the law of self-defense under the jus ad bellum. On this issue, in the Nuclear Weapons advisory opinion, the International Court of Justice (ICJ) stated: “But at the same time, a use of force that is proportionate under the law of self-defence, must, in order to be lawful, also meet the requirements of the law applicable in armed conflict which comprise in particular the principles and rules of humanitarian law.”
This may mean that to determine whether an act of self-defense fulfills the condition of proportionality under the law of self-defense (the jus ad bellum), the interpreter must also consider whether the proportionality rule under the jus in bello has been respected. In other words, a series of attacks that cause excessive collateral damage can perhaps be considered disproportionate under the law of self-defense, in the sense that the acts were not necessary and proportionate to the aim of defending against the armed attack. Indeed, the excessive harm to civilians does not pertain to the area of defense but rather to unlawful attack. This would certainly be the case in instances where the collateral damage is massive and repeatedly excessive, because for single situations it could still be argued that the attack was useful for defense, even if it harmed an excessive number of civilians. Conversely, if the attacks mainly injure civilians, the necessary links to defense become less clear.
An alternative view is to disaggregate both processes. According to its wording, this is probably what the ICJ suggested in the passage quoted above. The interpreter would then have to check separately whether the proportionality requirements have been met under the jus ad bellum and then under the jus in bello. In such a course, the principle of separation would be fully upheld.
But it does not seem to me that the first approach presented would represent a legal mistake. A practice of disproportionate attacks under the jus in bello could at least cast doubt upon the belligerent’s respect for proportionality under the law of self-defense pursuant to the jus ad bellum.
Another example flows from the law of occupation discussed above, which could also fit the present category. The interpretation of the word “hostile” in Article 42 of the Hague Regulations rests in significant part on classifications of the jus ad bellum centered around the consent or not of the government of the occupied State to the foreign military presence. According to that criterion, there is a belligerent occupation, or a pacific occupation at best.
It remains to be mentioned in passing that issues of cross-linked interpretation also arise outside the context of the relations between the jus ad bellum/jus in bello strictly speaking. An example is humanitarian assistance. It stands to reason that provisions like Article 70 of AP I (relief actions) have to be interpreted in light of the many UN General Assembly and Security Council Resolutions (some under Chapter VII of the Charter) giving shape to or requiring such humanitarian aid (see the classical Resolutions 43/131, 45/100, and 46/182 of the UN General Assembly). There is here a corpus juris which has been developed over the years, which it would be preposterous not to take account of when interpreting single jus in bello provisions, to the extent precisely that these provisions are not a derogatory special law regarding the general principles set out in UN law. On the contrary, both branches of the law pull in the same direction and have the same aims. Such UN sources may be relevant especially to determine what is meant by an “arbitrary” refusal of aid.
Conclusion
As can be seen through the analysis of these four categories, the principle of separation is less strict than is often conceded. Concentrating merely on the main aspect of the matter, which is to ensure the proper and equal application of the jus in bello, there has been some overstretch of the principle of separation. Under critical analysis, the latter is strict in some areas and weak in others. The aim in emphasizing the exceptions to the principle is not to undermine its main area of application. Under international law as it stands, the presumption is and remains that the jus ad bellum and jus in bello are separate. Therefore, separation remains the rule, contamination is the exception. But it is possible to carve out exceptions to that principle in certain areas of the law, when such exceptions are based on explicit rules of international law stemming from treaties or generalized accepted practice.
It is true that there have been attempts to undermine the separation principle much farther and to deprive it of any firm status in international law. For example, it has been said that the jus in bello should not be applied to the “barbarians” (terrorists) after 9/11, when the United States exercised its legitimate right of self-defense under the jus ad bellum. But such positions have not prevailed. The separation has remained the principle and the presumption to which there are some exceptions. To some extent, these exceptions smooth out the principle and oil its wheels. For few things on this earth can function in crystalline purity and heavenly clarity. In society, and thus in law, most things must be pondered carefully and balanced up one against the other by taking account of the many countervailing gravitational forces and paradoxes of our complex legal reality.
***
Robert Kolb is a Professor of Public International Law at the University of Geneva and former legal staff member of the ICRC. Prof Kolb is also a member of the legal section of the Swiss military high command (IHL section).
The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense.
Articles of War is a forum for professionals to share opinions and cultivate ideas. Articles of War does not screen articles to fit a particular editorial agenda, nor endorse or advocate material that is published. Authorship does not indicate affiliation with Articles of War, the Lieber Institute, or the United States Military Academy West Point.
Photo credit: U.S. Army, Joseph Kumzak
