On Robert Kolb’s Advanced Introduction to International Humanitarian Law, Second Edition
This post provides select reflections based upon the experience of writing the second edition of my book, Advanced Introduction to International Humanitarian Law (Edward Elgar Publishing 2025).
I wrote the book as an “advanced” introduction, in the sense that it does not cover all issues of international humanitarian law (IHL) in a didactically coherent sequence, allowing the beginner to build up, piece by piece, tokens of knowledge. Rather, it was written to shed light on a series of gravitational aspects of IHL, be it in the domain of the positive law as it stands today or in the domain of its historical growth.
Overview of Revisions
The new edition is composed of nine substantive chapters including: 1) the main epochs of modern IHL and their related legal constructions; 2) international armed conflict (IAC) and non-international armed conflict (NIAC); 3) sources of IHL and their subject matter specificity; 4) main principles of IHL; 5) applicability issues and finding a way out of the quagmire; 6) combatants and civilians – a sometimes difficult divide; 7) targeting – a context-related legal set of rules; 8) neutrality and its relative demise; and 9) implementation of IHL law – the Achilles heel of the system.
What is new in the second edition? Three aspects can be noted. First, developments on the “global war on terror” were largely suppressed. Those issues featured prominently in the years after the September 11 attacks and spawned a wealth of writings. In more recent years, however, new problems have taken the forefront. They include especially the consequences of the Russia-Ukraine armed conflict and its various ramifications (such as on the law of neutrality). I thus decided to suppress entirely the excursus on the “war on terror” limb to provide some space for new developments.
Second, I partly revised some chapters by inserting new content. I placed particular emphasis on the complexities of treaties in IHL, as has been shown quite recently by the exploding Israeli pagers and communicators used by Hezbollah in Lebanon. I also added materials on the interplay between IHL and international human rights law.
Third, some chapters and sub-sections are completely new. This is the case with the chapter on neutrality, put into glaring light by the Ukraine-Russia war. It is also the case for sub-sections on the role of unilateral engagements in NIACs, for the distinction between Hague and Geneva Law, for the distinction between jus ad bellum and jus in bello, and last, for ways of improving IHL compliance by armed groups in NIACs.
Not all these novelties can be commented upon in this post. Instead, it focuses on four issues: 1) the exploding pagers (law of treaties); 2) the distinction between jus ad bellum and jus in bello; 3) improvements to IHL compliance by armed groups in NIACs; and finally, 4) neutrality.
The Pagers Affair
The pager and walkie-talkie attacks by Israel on Hezbollah fighters in Lebanon in 2024 illuminate many complexities of treaty law in the context of IHL. Apart from the general law on proportionality, reflected in Additional Protocol I (AP I), Article 51(5)(b), the attack raised questions concerning the special law on boobytraps which could apply. On this latter point, Article 6 of Protocol II to the 1980 Convention on Certain Conventional Weapons (CCW), first in its 1980 version, then in its revised version of Article 7 of the 1996 Amended Protocol II seems especially relevant. Yet the text of the 1996 version is more sweeping and can encompass acts which are not covered by the 1980 version.
Further, the attack raised the issue of armed conflict classification. If the hostilities between Israel and Hezbollah amount to an IAC, CCW Protocol II could in principle apply if Israel and Lebanon are parties to it. If a NIAC, the ratification or accession is for Israel alone. A further complication is that under its Article 1, Protocol II applies as a matter of principle only in IACs. But there is a 2001 revised version of Article 1 of the CCW, which extends the application of the Convention and its Protocols to NIACs. However, the 1996 Amended Protocol II’s first article includes the same clause of extension to NIACs.
Therefore, the precise legal status of Israel and Lebanon to these instruments is relevant. Israel joined the 1980 CCW, the 1980 Protocol II in 1995, and the 1996 Amended Protocol II in 2000. For its part, Lebanon has joined the CCW, the Amended Protocol II of 1996 in 2017, but not the 1980 Protocol II. Israel has neither ratified nor acceded to the 2001 amendment of Article 1 of the CCW. But it made a declaration in its 1995 accession to Protocol II whereby it will apply the provisions of the Convention also to NIACs. This was a unilateral statement which we can take as binding, so long as it has not been withdrawn. Lebanon is a party to the revised version of the Convention. The acts at stake took place in 2024, thus there is no problem of temporal (retroactive) application of the relevant treaties.
Concerning classification of the conflict, three lines of argument are possible. A first view considers the situation as a NIAC only; the belligerent relationship is between Israel and an organized armed group (Hezbollah). A second considers it a mixed conflict; there is a NIAC between Israel and Hezbollah and at the same time an IAC between Israel and Lebanon, because the hostile action took place on the territory of the latter and had impacts on its population and infrastructure. Under a third view, there is an IAC only; Hezbollah is not an armed group but wields governmental power in Lebanon, and thus it is a State organ, at least de facto.
In the case of a NIAC between Israel and Hezbollah, the first view above, the 1996 Amended Protocol II is applicable, as Israel has acceded to it. Israel has not entered any relevant reservations to this provision of Amended Protocol II (art. 1, § 2), which specifies extension to NIACs as understood by common Article 3 to the 1949 Geneva Conventions (including extraterritorial action).
As for substantive regulation of the exploding devices, the 1980 Protocol II, with its more restrictive text under Article 6, is not applicable. Article 7 of the 1996 Amended Protocol II version is instead applicable as the later-in-time law (lex posterior). Moreover, even if Amended Protocol II did not include the clause extending it to NIACs, it could still apply to the facts at hand because Israel has entered a declaration to that effect in its initial accession of 1995. If that declaration had not been made, only the 1980 version would be applicable under the law of treaties.
In the case of the conflict being classified either as mixed or as a pure IAC between Israel and Lebanon, the 1996 Amended Protocol II is applicable, as both Israel and Lebanon are States party from the date of the later accession, 2017. IHL applies reciprocally in an armed conflict. Action by one State is not sufficient to trigger the application of all the treaties it has ratified or acceded to. Rather, it must be ascertained that the treaty is binding on both States, the acting one and the one suffering the action (here on its territory). If that were not true, the reciprocity of application of IHL would be lost. Israel would be bound in its actions by Protocol II, but Lebanon would not be bound if it committed similar acts on Israeli territory.
Overall, this episode illustrates that a complex series of IHL treaty law questions must be checked as a preliminary matter prior to application of any substantive rule of IHL. First, because two versions of the CCW Protocol II differ on a relevant provision careful assessments of the various belligerents’ status as parties must be resolved. Second, the character of the armed conflict itself is relevant. The 2001 amendment of the CCW extending it to NIACs requires further investigation with respect to the character of hostilities involving each party. Further, the 1996 Amended Protocol II clause on extension to NIACs, which does not appear in the 1980 Protocol II, must be also be addressed. And finally, declarations and reservations made at the time of those ratifications and accessions must be accounted for.
It is hoped this illustration of treaty matters in the second edition adds to readers’ appreciation of rigorous IHL application and analysis.
Distinction between Jus ad Bellum and Jus in Bello
The second edition also devotes attention to an important international law framing issue. In modern international law, a cardinal principle requires the separation between jus ad bellum and jus in bello. The motivating sentiment is to guarantee the equality of belligerents in the application of the rules of IHL. The principle means that whatever the justification for the use of force, whether it is lawful under international law or whether it is unlawful, the belligerents must reciprocally apply the same rules of IHL (under customary law as well as those treaties that are applicable between the parties).
What are the main reasons for the separation of jus ad bellum and jus in bello? A first reason is humanitarian. When applicable, the humanitarian protections of IHL are “absolute” in nature and must be always honored. That an adversary uses force in self-defence against an aggressor State should not undermine protection of the latter’s civilian population, its fighters placed hors de combat, or captured members of its armed forces.
A second reason is structural. No specific mechanism in international law operates universally to determine the legality of resorts to force. Most commonly, States assess their legal situation for themselves. The usual consequence is that each belligerent proclaims itself a victim State or otherwise justified in its resort to force. To permit exemptions from IHL or the jus in bello on the basis of jus ad bellum victimhood thus, would inevitably involve unbridled license to derogate and subsequent IHL collapse.
A third reason is pragmatic and concerns the role of reciprocity. Although this condition has been limited in modern IHL, the fact remains that reciprocity is still an essential driver of the application of the rules of international law. Often, when a State fears reprisals from another State, it will refrain from violating rules. On the contrary, if another State does not apply a rule, the victim State also often ceases to apply it as well. Consequently, without equal application of the rules of IHL by the belligerents, IHL risks falling into a spiral of “reprisals” and “counter-retaliations.” The rules on maritime warfare demonstrated this very well during the First World War. Unlimited warfare by German submarines collapsed the entire normative edifice.
On close examination then, several detailed doctrinal consequences attend the jus ad bellum – jus in bello separation. First, there are no distinctions allowed in the application of IHL according to the reasons for which armed force is used. Second, the fact that IHL is respected does not justify the use of force. Third, violation of one branch of the law does not mean ipso facto the violation of the other. Fourth, justifications occurring in one branch of the law do not extend to the other (e.g., invitation to use force in a jus ad bellum sense does not give license to breach the jus in bello). Fifth, the triggering element for the application of both branches remains separate. A “use of force” in the jus ad bellum sense on the one hand, may be distinct from an “armed conflict” in the jus in bello sense. Finally, jus ad bellum arguments may (normally) not be used in the context of applying or interpreting jus in bello obligations (e.g., by taking into account the liberation of national territory as a “military” advantage in the balancing process against collateral damage for in bello proportionality purposes).
The second edition of my book also explores the principles of separation and equality of belligerents in various forms of armed conflict. These apply primarily to IACs and do not have full application in NIACs. In the latter case, armed groups are generally considered seditious, terroristic, or simply criminal by the governments fighting against them. Given that IHL is codified by States, we cannot expect those same States to grant these groups the status of equal belligerents. The lack of equality can be seen in the absence of combatant status for members of armed groups under national criminal law. A second area of law in which the principle of equality of belligerents does not strictly prevail is that of neutrality. Discrimination against an aggressor State is required, especially by applying the sanctions (e.g. on weapons embargos) taken by the Security Council under Chapter VII of the UN Charter. In modern international law, compliance with sanctions decreed by the Security Council does not expose a State to the reproach of having violated the law of neutrality.
Although separation of the jus ad bellum and jus in bello is strict concerning equal application of the rules of IHL in IAC, in other areas, the two branches of law can interact more or less closely through reciprocal influences. Violation of certain rules of IHL, such as proportionality, can lead to a violation of proportionality in the law of self-defense. So too can a resolution of the UN Security Council authorizing the use of force designate certain objects to be destroyed, beyond the objects that IHL allows to be attacked (per AP I, art. 52(2)).
But there are even more obvious interactions, again running both ways. If a State consents to receive foreign military forces in its territory (intervention by invitation under the jus ad bellum), the presence of these armed forces does not trigger a belligerent occupation in the in bello sense. Rather, as set out by the agreement concluded between the concerned States, it is a “peaceful occupation,” to which the jus in bello will not apply.
The above points notwithstanding, account must be taken of the tendency of many States to reduce the principle of separation. Voices raised at various moments in history and in the present have appeared to favor and claim legal concessions for a belligerent, when it fights against “barbarians,” “outlaws,” “criminals,” or “terrorists.”
Improving IHL Compliance by Armed Groups
It is increasingly appreciated that IHL compliance in NIACs varies widely according to the type of armed group involved in fighting. The second edition of my book explores and seeks to explain this phenomenon as well as to propose some steps to improve compliance.
As a general matter, armed groups (AG) that are highly organized and impose thorough discipline have better opportunities to implement rules of IHL. Yet compliance also depends on the aims of the group in question. AGs that fight for political aims (e.g. secession and creation of a new State, seizure of governmental power) usually seek a certain degree of respectability and are often amenable to the rules of IHL. On the other hand, AGs interested in criminal enterprises or monetary gain (e.g., exploitation of resources, traffic in drugs, abductions, etc.) see little to gain from IHL. There is thus a wide spectrum of compliance culture among AGs and the question must be assessed almost on a case-by-case basis.
Additionally, two inherent problems accompany the problem of compliance by AGs. First, there are, in some circles, unrealistically high expectations and demands. Some particularly militant international lawyers do not hesitate to postulate excessive interpretations or extensions of IHL rules and other wartime legal duties. Purported obligations arising under international human rights law illustrate the point well. The material ability to satisfy such duties may be considerably reduced or even excluded in the case of many AGs, particularly during conflict. The same may be said, for example, for extensive command responsibility obligations, tailored to well-organized armies of States but hardly fitting for loosely knitted AGs. High command responsibility demands on AGs lead to disaffection with the law and ultimately to tendencies of indifference and disrespect.
Second, there is the famous “ownership” gap in NIAC. IHL is made by States through the treaties they join, or the consistent practices they follow from a sense of legal obligation. It is then difficult to require that an AG follow law that they had no role in shaping and, worse, which emanates from their “enemy.” There are devices for softening this “ownership” deficit. One such device, followed by Geneva Call, is to entice AGs to sign their own commitments as to the IHL they will respect.
The following, then, can be done to enhance the compliance of AGs with IHL. States might afford AGs greater participation in making the rules. Additionally, better and more proactive dissemination of IHL rules, in a culturally sensitive way, may reduce compliance barriers. Further, securing signed commitments to apply a given set of IHL rules or IHL generally (see notably the Geneva Call database) can better guarantee conduct consistent with IHL. More concretely perhaps, adopting policies to reward respect for and compliance with IHL (e.g. by obtaining some privileges in case of capture) can be a powerful compliance tool. Finally, closer monitoring of respect for the rules and more regular sanctions for violations (notably through criminal law procedures but possibly also through civil law claims) can exert significant compliance pull.
Neutrality
Finally, the second edition presented an opportunity to revisit the law of neutrality. Neutrality concerns the position of States which do not participate in an armed conflict. The law of neutrality concerns more precisely the legal position of these third States, in public international law and according to their internal legislation. Neutrality in the legal sense of the term presupposes an IAC of a certain intensity (a “war” in the old sense of the word). There is no law of neutrality in the event of a NIAC.
The law of neutrality has never been fully consolidated into strict rules. It is a moving area of the law, of a customary nature, resulting from the practice of States. The codified rights and duties of neutrality date back a long time including the Hague Convention V on Neutrality in War on Land; and Hague Convention XIII on Neutrality in Maritime Warfare, both of 1907. Apart from these sources of international law, there are domestic laws on neutrality or on related matters, e.g. delivery of arms abroad. For instance, while Switzerland does not have a domestic neutrality law, it has laws on supplying arms to foreign powers.
Related to this international and domestic divide, an important distinction must be made between ordinary neutrality and permanent neutrality. The first concerns the situation of States not bound by treaties or internal legislation in this area. When an IAC breaks out, a State may choose to participate in it (for instance through collective self-defense of a victim State) or stay out of it (and remain neutral). A State may even, in violation of international law, participate on the side of the aggressor. Ordinary neutrality always comes after the fact. It presupposes the existence of an IAC and a choice that the State concerned makes from that moment.
By contrast, permanent neutrality is based on conventional commitments or on internal legislation. It obliges the permanently neutral State never to participate in an armed conflict and therefore to take, in time of peace, measures to avoid being drawn into an armed conflict (such as a prohibition on joining a collective self-defense alliance). The neutral State can, however, prepare its own defense and maintain links with military alliances in order to repel a possible attack on its territory. For it goes without saying that once attacked by a belligerent, the neutral State becomes a belligerent and does not violate its neutrality by defending itself.
The second edition provided an opportunity to highlight a further distinction between the rules on land neutrality and those on maritime neutrality. Land warfare is a kinetic war of destruction; maritime warfare is essentially economic warfare. Consequently, land neutrality concerns above all participation in military activities or support for them; economic resources do not play a role. On the contrary, maritime neutrality is founded on the fact that the belligerents will try to cut off the commercial supplies of the opposing state. Neutrality is therefore colored with a commercial and economic patina. Thus, in the maritime area question of prizes, contraband and unneutral services will loom large.
In a substantive sense, the law of neutrality contains only minimal prohibitions. The position of the neutral State is already uncomfortable; it suffers the consequences of an armed conflict that it did not choose. States therefore refrained from aggravating the neutral State’s position by encumbering it with numerous duties. Thus, the neutral State is not, according to traditional law, obliged to prohibit trade in arms towards a belligerent on the part of individuals and private companies (Hague Convention V, art. 7). Also, the neutral State is not obliged to reduce trade with belligerents or treat them equally in trade flows.
What are the essential contents of the right of neutrality? There are three duties involving abstention, action, and tolerance respectively.
There must be no State support for a belligerent by sending troops, delivering weapons, making territory available for acts of hostility, allowing overflying, or crossing neutral territory for arms or by troops, transmitting military information, granting of credits for the purchase of military equipment from a belligerent, etc. If the State adopts restrictive measures concerning arms trade by private actors, it must treat all parties to the conflict equally.
The neutral State must act to repress on its territory, with the means at its disposal, any act contrary to its neutral position. If it fails, in the most serious cases, the injured belligerent will have a right to intervene on neutral territory to put an end to the violation of neutrality.
The neutral State must tolerate certain acts on the part of the belligerent parties, for example the visit and control of its ships on the high seas (right of “visit and search”).
In the modern law of neutrality, there is significant development mainly on two issues: the insertion of neutrality into a system of collective security; and the rise of an intermediary position not yet well-defined, i.e. non-belligerency.
The classic neutrality of the 19th century was situated, as we have seen, in a double relationship of largely untrammeled recourse to force and of pure inter-State relations. The 20th century saw the emergence of collective security systems, distinguishing between lawful and unlawful uses of force. In the event of an unlawful use of force, a collective organ (nowadays the UN Security Council) can take coercive measures to sanction and/or combat aggression. For the members of the international organization carrying such a system of collective security (and also for any non-party States), it is not possible to argue neutrality in order not to implement the sanctions decided by the Council. Moreover, when the latter authorizes the use of force under Chapter VII of the UN Charter, we are no longer in the context of a classic “war” (in terms of purely inter-State relations), but in the context of an enforcement mandate from the World Organization (triangular relationship: States and Organization), which, from the perspective of the law of the Charter, is similar to something akin to a “police action.”
However, no State is obliged to send troops. The Council does—and can only, as things stand—authorize the use of force to fight the offending State. There is no obligation to send troops. Conversely, a Member State of the UN cannot refuse to participate in the sanctions, coercive but peaceful, which the Council decides. This is why, even before Switzerland’s participation in the World Organization, in a 1993 report, the Swiss Federal Council considered that the right of neutrality did not apply to non-military sanctions taken by the Council, or even to similar sanctions and countermeasures adopted by other organizations (notably the European Union). In legal jargon, we will usually speak of “differential” rather than “integral” neutrality.
Equally, there is the progressive development of an intermediary position between the old categories of “belligerency” and “neutrality.” Certain violations of the law of neutrality create a state of belligerency. For example, this is the case if a neutral State sends troops to support a belligerent. But this is not the case for all violations of the law of neutrality. The supply of arms, for example, does not make the State which supplies them a party to the conflict. It does not even give an option of self-defense to the injured State, as the International Court of Justice correctly decided in its Paramilitary Activities judgment (para. 195). If this were not so, the territory of a State supplying arms could be bombarded, since it would henceforth be the territory of a State participating in the conflict.
However, if that State is not a belligerent, it is also no longer a neutral. Sending weapons is not compatible with neutrality and would, if the State proclaimed itself to be neutral, be a flagrant breach of its duties. Therefore, between respected neutrality and becoming a party to the conflict there are nowadays a series of intermediate positions. These are usually legally summed up in the notion of “non-belligerency.” In the context of Ukraine, the United States, France, the Netherlands, Denmark, Germany and many others are non-belligerent States. They are clearly not neutral States.
In fact, the tendency of most States today, when confronted with an IAC, is to not be fully neutral, but to depart from neutrality to provide varying degrees of assistance to one belligerent. It is difficult to argue that all these States are simply violating their duties of neutrality. This is because they do not claim to be neutral in the first place. In modern international law, there is no automatic neutrality. Neutrality is now claimed, by way of declarations of neutrality.
The recent conflict in Ukraine has shown a great number of shades of support departing from neutrality including delivery of military intelligence, supply of weapons, and financing the war effort, etc. There has been almost no protest against these actions, which are manifestly incompatible with the law of neutrality. Thus, it seems that an intermediary status is continuing to chart its way: belligerency; neutrality; and non-belligerency.
The latter concept does not yet enjoy clear content. It may mean that a State is neither belligerent nor neutral (a residual category). If this residual category is one of mere fact or rather a legal status is not yet clear. It is also not clear what types of actions it encompasses, beyond the most obvious, such as the delivery of weapons. It is often claimed that this category is not yet established in international law. However, there is no necessity to have such prior recognition. Because there is generally neither a duty to remain neutral nor to become belligerent in international law, States are free to be “non-belligerents” under the umbrella of their Lotus-freedom, i.e., under the argument that what is not prohibited (but here even legally allowed) by international law is lawful. Hence, there is also no necessity to root non-belligerency in the law of countermeasures. The law of neutrality does not have to be set aside by invoking a previous breach of international law, there being no obligation to remain neutral in the first place. If such an intermediary position is taken more and more often, and accompanied by a legal conviction, it will turn into a customary rule of international law.
All these developments mean that a new assessment of the law of neutrality and its normative surroundings will become necessary.
Conclusion
In sum, the opportunity to revise and update my text, Advanced Introduction to International Humanitarian Law, proved a valuable exercise in surveying recent developments in and challenges facing IHL. My approach was to lend the text a refreshed accounting of the context in which this most complex and critical body of law functions. Ongoing conflicts, both IACs and NIACs, have shined new light on old problems, but have also revealed new fault lines in the existing law. It is hoped this volume results in a more informed IHL dialogue between States and their various constituencies. I also hope it inspires pragmatic solutions, informed both by the call of humanity and the realities of warfare, to the many challenges facing this most important discipline of international law.
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Robert Kolb is a Professor of Public International Law at the University of Geneva and former legal staff member of the ICRC.
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: Pexels, Edward Elgar Publishing
