Introduction
Since the beginning of the third millennium, the battlefield reality has undergone significant changes, a trend that is expected to continue in the coming decades.Footnote 1 Technological advancements have led to increasingly sophisticated means of warfare, prompting new debates on emerging issues such as lethal autonomous weapons systems (LAWS)Footnote 2 and hypersonic weapons.Footnote 3 These technological innovations also open up new domains for warfare, particularly in cyberspace and outer space.Footnote 4 The ongoing international armed conflict (IAC) between Russia and Ukraine clearly illustrates that contemporary hostilities already heavily rely on cyber-based and space-based capabilities.Footnote 5
Moreover, as weaponry and battlefield locations evolve, certain categories of belligerents have gained greater prominence and visibility in armed conflicts. These include transnational organized armed groups such as Al-Qaeda and the so-called Islamic State group (IS), which have operated across several countries, as well as private military and security companies such as the Wagner Group.Footnote 6 Further, the increasing complexity of the battlefield is also evident in the growing interactions between actors, for example in terms of belligerent cooperation. Since the start of the century, such cooperation has been widely observed within non-international armed conflicts (NIACs), especially in the context of the global fight against terrorism,Footnote 7 but also in IACs, as exemplified – again – by the ongoing IAC between Russia and Ukraine, as both States have received various forms of military assistance.Footnote 8
In light of all this, with the new millennium, it is almost an understatement to note that armed conflicts are rapidly evolving across multiple dimensions – material (the military equipment being used), personal (the nature of and interactions between the belligerent parties) and geographical (the various domains of warfare).
These ongoing transformations on the battlefield compel international humanitarian law (IHL) to adapt. The notion of effectiveness is central to understanding this imperative for adaptation. In international law, including IHL, effectiveness originally refers to the principle of effectiveness. With philosophical roots in the work of Niccolò Machiavelli and Georg Wilhem Friedrich Hegel, this principle entered the international legal order during the second half of the nineteenth century,Footnote 9 notably through an IHL instrument.Footnote 10 The rise of positivism provided the ideal environment for its emergence.Footnote 11 The principle of effectiveness was further developed in international legal scholarship during the first half of the twentieth century,Footnote 12 often associated with Hans Kelsen’s writings.Footnote 13 If one still accepts today the existence of such a principle (as the present author does),Footnote 14 it presupposes a dynamic dialogue between tangible realities and the legal norms that seek to regulate them.Footnote 15 In other words, the principle calls upon IHL to remain attuned to the realities of the battlefield and thus “to be a realistic and pragmatic body of law”.Footnote 16
This being said, even for those who do not acknowledge the existence of a distinct principle of effectiveness,Footnote 17 it is difficult to deny that effectiveness – in its modern and broader senseFootnote 18 of success “in achieving what is wanted”Footnote 19 – requires some connection between law and fact. In this broader meaning, the effectiveness of a legal regime is defined by its capacity to secure compliance and to impose sanctions in cases of violation.Footnote 20 Actors are unlikely to respect a body of law that appears outdated when compared to tangible realities. Therefore, experts who discard effectiveness as a principle would, nevertheless, probably agree that, for IHL to remain effective, it must continually reassess whether its existing framework is adequate to regulate new challenges on the battlefield.
This article argues that analogical reasoning plays a crucial role in addressing IHL’s adequacy to govern emerging battleground realities. It explores contemporary IHL discourses relating to evolving factual circumstances and the emergence of new norms or interpretations, demonstrating how extensively analogical reasoning is relied upon in the ongoing development of this branch of international law.
The temporal scope of this research begins in 2001. The start of the twenty-first century undoubtedly marks a turning point for IHL, with the exponential acceleration of technological progress and the tragic events of 11 September 2001 ushering in a new era of crisis, particularly for the law governing NIACs. The choice of time frame also situates the article as a continuation of a previous contribution published in this same forum.Footnote 21
Following some useful preliminary reminders as to the definition and structure of analogies, the article examines the dual function of analogical reasoning in contemporary IHL literature and practice. This dual function is illustrated through five paradigmatic examples addressing some of the most pressing issues on the battlefield: LAWS, cyber operations, outer space warfare, NIACs, and belligerent cooperation in both NIACs and IACs. The article then considers the limitations and risks associated with the important use of analogies in the evolution of IHL.
Preliminary reminders
While this article does not intend to delve into all theoretical intricacies of analogical reasoning, a few foundational remarks are necessary.Footnote 22 For the purposes of this research, analogy is broadly understood as “the importation of knowledge from a well-known source onto a less well-known target by the establishment of correspondences between the two”.Footnote 23 From a legal perspective – drawing on cognitive science – the “source” is thus a term of art which refers to a situation that is already governed by law and serves as the analogical reference point, while the “target” is the corresponding term of art which denotes a new, unregulated situation for which analogical inspiration is sought from the existing legal framework of the source.Footnote 24
More specifically, analogical reasoning encompasses two variants relevant to this article. First, it may refer to a similarity of terms between the source and the target, allowing for the extension of the legal regime from the former to the latter. In his work on analogical reasoning in international law, Jean Salmon explains that
il arrivera plus souvent qu’à son tour que l’interprète nourrira des doutes sur le point de savoir si les faits concrets soumis à son examen tombent bien dans les faits juridiques décrits par la règle. Si ces faits ne sont pas entièrement identiques à ce que prévoit la norme, s’ils leur ressemblent par certains aspects, mais en diffèrent par d’autres, la décision de les inclure dans la norme relève, à proprement parler, d’un raisonnement par analogie.Footnote 25
In other words, in a similarity of terms, the resemblance (similarity) is primarily factual in nature: the known factual circumstances of the source (as captured by its legal framework) are similar, although not identical, to the new factual circumstances of the target. As a consequence of this factual similarity, the same legal regime can be argued, through analogy, to apply to both the source and the target, resulting in an identity of applicable norms. The legal framework developed for the source can therefore be extended to the target, even though the drafters or designers of that framework did not originally envisage the factual circumstances underlying the target situation.
Second, and alternatively, analogy may also relate to a similarity of relations. This means that the legal framework designed for the source helps illuminate what the legal framework for the target is or ought to be. The source and target do not actually share the same legal rules, but the legal regime of the target is inspired by that of the source. Writing on legal methodology, Véronique Champeil-Desplats notes on analogical reasoning that
[l’analogie en ce sens] établit que “A est à B” ce que “C est à D”. L’opération consiste à tenir pour équivalente deux relations entre des éléments différents, en étendant le lien connu entre deux premiers à deux autres.Footnote 26
Thus, the elements being compared are relations: the known relationship between the established factual circumstances of the source and its existing legal framework serves as a guide for understanding the unknown relationship between the new factual circumstances of the target and its (potential) legal framework. Hence, in contrast with similarities of terms, there is no identity at either the factual or the legal level. The established factual circumstances of the source are similar – but not identical – to the new factual circumstances of the target; the legal framework applicable to the source is also similar – but not identical – to the proposed legal framework for the target. The envisaged legal framework for the target builds upon, rather than replicates, the legal framework of the source.
Regarding its structure, analogical reasoning typically follows a three-step process, originally conceptualized in cognitive science and now widely accepted in legal theory. The retrieval step involves the cognitive act of selecting a relevant source or several relevant sources from memory. The mapping step requires identifying similarities and differences between the source and the target. Finally, the transfer step consists of extending and, whenever necessary, adapting the legal solution of the source to the target.Footnote 27
With these conceptual foundations in place, the next sections explain the central role of analogical reasoning in IHL’s ongoing development. After some general observations on the dual function of analogies within IHL, a series of thematic examples clearly demonstrate that the prominence of analogical reasoning in IHL today is not a mere illusion, but a fact reflected in the literature and practice. While analogies have not been treated as an independent subject of inquiry within IHL,Footnote 28 they are omnipresent in contemporary IHL discourses, whether in academic scholarship, State practice or the work of international institutions.
Centrality of analogical reasoning in contemporary IHL discourses
General observations: A dual function for IHL analogies
Research in IHL literature and practice on contemporary issues shows that IHL analogies fulfil two functions traditionally associated with analogical reasoning:Footnote 29 an interpretive function and a creative function. On the one hand, analogies play a significant role in interpreting existing IHL. On the other hand, they provide clues as to what future IHL could be.
An interpretive function for IHL analogies
When a new development occurs or, less frequently, is anticipated on the battlefield,Footnote 30 IHL experts and stakeholders typically begin by assessing, first, whether this branch of international law is applicable (as the applicability of the existing IHL framework is usually triggered by classical forms of armed conflicts where hostilities are conducted through common means and methods of warfare and by well-known actors), and second, whether it sufficiently regulates the emerging warfare situation. This approach is both necessary and welcome, especially given that States – the primary lawmakers in IHL – often struggle to follow the pace of technological advancements and battlefield evolutions, and may be reluctant to adopt new rules, although this possibility cannot be entirely discarded.Footnote 31
In assessing IHL’s resilience to battlefield evolutions, analogical reasoning helps determine whether the lex lata – the law as it stands – can accommodate these evolutions. Indeed, whenever a new warfare situation emerges on the battlefield, a recurring pattern of legal reasoning can often be observed in both IHL scholarship and practice: first, norm interpreters or norm appliers examine whether this new situation (target) is similar to a known warfare situation that is already regulated under IHL (source); and second, if they were able to identify enough similarities between the target and a source, they extend the scope of application of the existing IHL rule from the latter to the former. This legal reasoning is an analogical reasoning, and the relevant form of analogy is a similarity of terms, as previously defined.
In such cases, analogies follow the adoption of IHL norms and serve as a method of interpretation. Therefore, concerning IHL treaty rules, analogies must in principle operate within the interpretive boundaries established by the Vienna Convention on the Law of Treaties.Footnote 32 Through this interpretive function, analogical reasoning ensures the flexibility and dynamism of IHL norms. However, this presupposes that the language of IHL’s existing rules remains sufficiently general and not overly detailed, thereby leaving room for interpretation.Footnote 33
This interpretive function of analogies may be linked to the revisionist function of the principle of effectiveness, as identified by Jean Touscoz. Changes in social circumstances – in this case, developments in warfare – may lead to modifications in, or the evolution of, the content of existing rules, such as IHL rules.Footnote 34 According to the revisionist function of the principle of effectiveness, “[l]’interprète qui s’efforce de permettre au traité de remplir le plus complètement possible son rôle social devra donc adopter deux perspectives, conciliables et essentielles, la fidélité au texte et la dynamique du droit”.Footnote 35 In this respect, interpretation through effectiveness is more readily accepted when a considerable period of time has elapsed since the adoption of the relevant rules.Footnote 36 This is generally the case for the main rules of IHL, most of which were adopted during the second half of the twentieth century.
Research conducted for the present article reveals, as a general observation, that the interpretive function of analogies is manifest in documents addressing new technologies and emerging war theatres such as LAWS (Example 1 below), cyberspace (Example 2 below) and outer space (Example 3 below). As a more specific observation, it is interesting to highlight that this function is frequently apparent in informal law-making mechanisms, such as expert manuals. Notable examples are the two Tallinn Manuals on International Law Applicable to Cyber Operations (Tallinn Manuals).Footnote 37 Referring to the Tallinn Manuals, Pauline Charlotte Janssens and Jan Wouters note that, “[r]ather than developing an entirely new legal paradigm, [the authors] tried to extend the scope of existing rules of IHL to new circumstances by way of interpretation and analogy”.Footnote 38
A creative function for IHL analogies
After an initial assessment of the existing IHL framework, IHL experts and stakeholders may conclude that this framework does not, or does not sufficiently, address certain developments on the battlefield. Consequently, they may call upon lawmakers to adopt new rules and put forward proposals to that effect. As it is difficult to start from a blank slate, their proposals may rely on comparisons with well-established warfare scenarios and result from the adaptation of existing IHL rules. In these circumstances, such proposals constitute the outcome of analogical reasoning, the relevant form of analogy this time being a similarity of relations, as previously explained. The rules governing well-established warfare situations (sources) thus help determine and provide inspiration for what the applicable rules ought to be in response to these battlefield developments (targets). The latter rules are drawn from the former rules.
In this context, analogies perform a creative function. They precede the adoption of IHL norms and serve as a basis for de lege ferenda proposals. Although initially lex ferenda, these proposals may eventually become lex lata: they may be codified in a treaty (the conventional route) or be generally and consistently endorsed by States out of a sense of legal obligation, thereby crystallizing into customary norms (the customary route).Footnote 39
This creative function of analogies may be associated with what Jean Touscoz identifies as the creative function of the principle of effectiveness. According to Touscoz, “[l]’effectivité, c’est-à-dire la relation qui existe entre un titre juridique et la réalité sociale, relation étroite et durable, conditionne … la formation des règles juridiques internationales”.Footnote 40 When IHL no longer adequately reflects warfare realities, the principle of effectiveness may contribute to the emergence and development of new legal norms, relying on analogical reasoning as a particularly efficient tool.
Research conducted for the present article shows that the creative function of analogies is very common in developing the law of NIAC, as a subsequent subsection will illustrate (Example 4 below). Although the law of IAC is not directly applicable to NIACs, proposals for improving the law of NIAC are often inspired by IAC provisions. Additionally, in contemporary IHL literature and practice, analogies also play a similar de lege ferenda role in contexts other than the strict development of the law governing NIACs. They are used, for instance, to conceptualize belligerent cooperation – i.e., military assistance – in both NIACs and IACs (Example 5 below).
While the distinction between these two functions of IHL analogies may appear straightforward, an important caveat is necessary. For clarity purposes, the previous paragraphs have indeed separately presented the interpretive and creative functions of IHL analogies, as if they were two clearly distinguishable functions. As a matter of principle, analogies form part of the lex lata only if they are embedded in a formal source of international law recognized under Article 38 of the Statute of the International Court of Justice (ICJ), since analogy itself is not a source of law.Footnote 41 Nonetheless, the reader should not be misled: in the practice of international law – including IHL – where no centralized legislator exists, the boundary between interpretation and norm creation, as well as between lex lata and lex ferenda, is often blurred.Footnote 42 In reality, the distinction is not always as clear-cut as theory might suggest, and experts may reasonably disagree on certain questions (as illustrated by Example 5 below).
The following subsections thus explore the previously mentioned examples of the dual function of analogies in IHL’s ongoing development. It should be noted that these subsections do not aim to define the legal regime applicable to each warfare situation, nor do they exhaustively address all debates associated with them. Rather, their purpose is merely to highlight the central role of analogical reasoning in shaping contemporary IHL discourses.
Example 1: Lethal autonomous weapons systems
For over a decade, LAWS have continuously raised a wide range of issues – political, ethical and legal. Among the many legal challenges involved, it remains unsettled how LAWS should be definedFootnote 43 and how IHL can be concretely applied to LAWS. While addressing the definitional challenge lies beyond the scope of this article, the second issue is of great relevance here. In the absence of a specific IHL treaty governing LAWS, and despite some support for the adoption of new (complementary) rules,Footnote 44 many ongoing discussions concern the application of the existing IHL framework to LAWS and rely heavily on the interpretive function of analogical reasoning, with the preferred form of analogy thus being a similarity of terms. The (potential) presence of LAWS on the battlefield is often compared to existing warfare scenarios which are already governed by IHL rules. When the (potential) deployment of LAWS is considered sufficiently similar to one of these scenarios, the scope of application of the relevant IHL rules is extended to include LAWS, even though such weapons systems were not contemplated at the time those rules were adopted.
In the available scholarly works, two main sources of analogy are identified for the application of IHL to LAWS (target): the first source of comparison is a traditional weapon, while the second is a human fighting in an armed conflict (whether a combatant in an IAC, a member of an organized armed group in a NIAC or a civilian directly participating in hostilities in either an IAC or a NIAC). On the one hand, scholars use terms which describe LAWS as lifeless objects employed by persons – “artefacts”, “pieces of equipment constructed and utilized by people”Footnote 45 or “tool[s] in the user’s hands”Footnote 46 – thereby comparing them to traditional weapons. On the other hand, authors also underline that LAWS can independently select and engage targets, hence performing tasks that are typically performed by humans. LAWS are thus compared to humans, who are the known benchmark on the battlefield, leading one scholar to underscore that LAWS are sometimes considered to function as “replacements for humans … rather than as tools used by humans”.Footnote 47 As Rebecca Crootof aptly demonstrates, two primary analogies thus dominate the academic debate on IHL rules applicable to LAWS: the “weapon analogy” (comparison with existing weaponry) and the “combatant analogy” (comparison with humans fighting in an armed conflict).Footnote 48 The word “combatant” does not carry any technical legal meaning here, but merely the ordinary and broad meaning of “a person who fights in a war”.Footnote 49
These two main analogies often appear as alternatives, although some scholars have considered the possibility of combining themFootnote 50 and certain writings appear to address both simultaneously.Footnote 51 However, it is clear that the academic literature generally finds the “weapon analogy” more persuasive,Footnote 52 while the “combatant analogy” is described as “weak”,Footnote 53 “misleading”Footnote 54 or “untenable and irrational”.Footnote 55 According to the “weapon analogy”, LAWS constitute a new (descriptive) category of weapons over which human users (must) retain a degree of control in order to ensure compliance with IHL and accountability for their use.Footnote 56 As with any (new) weapon, they are already regulated under the existing IHL framework; this is consistent with the assertion of the ICJ, according to which IHL principles “appl[y] to all forms of warfare and to all kinds of weapons, those of the past, those of the present and those of the future”.Footnote 57 Nonetheless, even when this “weapon analogy” is preferred in scholarly writings, the tension with the “combatant analogy” sometimes remains discernible. For instance, Jonathan Kwik seems to favour the “weapon analogy”Footnote 58 but comes to compare LAWS to subordinates – i.e., humans – in the application of the proportionality principle.Footnote 59 It is worth noting that, beyond these two primary analogies of weapon and combatant, other legal analogies have been mentioned in the relevant IHL literature, such as analogies with animals, child soldiers or methods of warfare.Footnote 60
The importance of analogical reasoning in the IHL discourse on LAWS is therefore not a rhetorical flourish but is evidenced by its frequent and occasionally explicit use in academic writings. Several authors expressly acknowledge their analogical method,Footnote 61 while others refer to it more implicitly through terminology characteristic of analogical thinking and its cognitive steps, such as “translation”,Footnote 62 “extension”,Footnote 63 “adapt(ation)”,Footnote 64 “different”,Footnote 65 “mapping”,Footnote 66 “comparable”/“similar”Footnote 67 and “comparison”.Footnote 68
Admittedly, outside scholarship, there is no explicit evidence that any analogical reasoning has been used in practice in the discourse on LAWS, particularly by States – through the Group of Governmental Experts on Emerging Technologies in the Area of Lethal Autonomous Weapons System (GGE) – and by the International Committee of the Red Cross (ICRC). Available documentation from the GGE or the ICRC generally does not disclose any clear analogical reasoning. The only certain conclusion from numerous official documents adopted over the years by the GGE and ICRC is that both conceive of LAWS as “weapons” or “weapon systems” and, thus, as “means of warfare”. However, these official documents do not really express the reasoning method for classifying LAWS as weapons. For instance, the GGE developed a series of guiding principles about LAWS, the first of which states: “International humanitarian law continues to apply fully to all weapons systems, including the potential development and use of lethal autonomous weapons systems.”Footnote 69 This principle was approved by all States party to the Convention on Certain Conventional Weapons in 2019.Footnote 70 In its 2025 position paper, the ICRC affirms that “[L]AWS can be considered as constituting ‘weapons’ for the purposes of IHL”.Footnote 71 This being said, although no definitive conclusion can be reached, the available evidence suggests that analogical reasoning may not be wholly foreign to the reasoning process of the ICRC, as exemplified in its 2024 report on International Humanitarian Law and the Challenges of Contemporary Armed Conflicts:
It is an exercise in false equivalence to compare a human decision to launch an attack with a machine process that triggers the application of force. A more accurate comparison would be between a human launching an attack using a weapon system that is not autonomous and a human launching an attack using [a] [L]AWS.Footnote 72
Example 2: Cyber operations
Beginning at the end of the 1990s and more clearly emerging in the early 2000s, cyber operations have become a growing concern for IHL experts and stakeholders. Even though no known armed conflict has so far been conducted exclusively through cyber means, it is widely anticipated that belligerents will increasingly rely on cyber capabilities not only for intelligence, surveillance and reconnaissance operations, but also to disrupt, degrade, disable or damage adversary systems.Footnote 73 The ongoing armed conflict between Russia and Ukraine does not support a different conclusion: “the number of (cyber)attacks, the perpetrators, and the use of cyber against critical infrastructure” in this conflict were already being described as “cause for alarm” in September 2023.Footnote 74 Nevertheless, cyber operations remain a battlefield reality that is not specifically governed by IHL, and as a result, analogical reasoning has been explicitly identified as a key interpretive technique for applying existing legal norms to this new domain of warfare.Footnote 75 Indeed, in this very same forum, Paul Stephan has indicated that, “[a]s to cyber-operations, very little international law exists except by way of analogy”.Footnote 76 Again, as with LAWS, analogies are here understood as similarities of terms: IHL experts and stakeholders draw parallels between cyber operations and classical wartime operations, and then apply to the former the same legal rules that have traditionally governed the latter.
Even in the absence of direct references to analogical reasoning, the vocabulary employed by IHL scholars is revealing – just as it was in the context of LAWS. Terms such as “adaptation”, “translation” or “reinterpretation” – which correspond to the third step of analogical reasoning (transfer) – are frequently found throughout the relevant literature.Footnote 77 Moreover, IHL experts often compare the evolution and adaptation of IHL for cyber operations with its historical development in other domains, such as maritime or aerial warfare.Footnote 78 These comparisons also bring out the importance of analogical reasoning – albeit perhaps unintentionally – because, as this author has already demonstrated in this forum, analogies played a central role in shaping IHL in those domains.Footnote 79
The most encountered analogy in IHL literature on cyber operations links these operations to kinetic ones in the context of the conduct of hostilities (the analogy may apply to cyber operations as such, but also to cyber attacks or cyber weapons). By identifying similarities and differences between these types of operations, IHL scholars and stakeholders seek to determine how IHL should adapt in order to effectively regulate cyber activities. Whether embraced or contested, this analogy is prevalent in academic discourseFootnote 80 and in the writings of the ICRC.Footnote 81 For instance, in its updated Commentary on Geneva Convention IV (GC IV) protecting civilians (released in November 2025), the ICRC states:
It is generally accepted by experts, and reflected in the positions of a growing number of States, that cyber operations having similar effects to traditional kinetic operations would amount to an international armed conflict and would have to be conducted in accordance with the rules on the conduct of hostilities. Indeed, if these operations result in the destruction of civilian or military assets or cause the death or injury of soldiers or civilians, there would be no reason to treat the situation differently from equivalent attacks conducted through more traditional means and methods of warfare.Footnote 82
As the ICRC underlines in its Commentary on GC IV, the importance of this analogy between cyber and kinetic operations is also reflected in State practice: numerous States, including the United Kingdom,Footnote 83 Austria,Footnote 84 Denmark,Footnote 85 IrelandFootnote 86 and New Zealand,Footnote 87 refer to this analogy in their official position papers on the application of international law to cyber operations.
In addition to this general analogy which provides a broad guideline concerning the application of IHL to cyber operations, more detailed analogies appear in the academic literature and in State practice in relation to specific IHL provisions. These analogies revolve around the same idea of comparing cyber to kinetic or other traditional warfare situations, and they also exemplify the interpretive function of analogical reasoning. For example, Jeffrey Biller briefly examines for the purposes of Article 16 of Geneva Convention II whether crew members of a ship should be considered to be captured by, and thus “fallen into the hands of”, the cyber operator exercising control over the ship.Footnote 88 To support his analysis, he draws a parallel between a helicopter controlling enemy troops on the ground (with no help from accompanying ground forces) and such a cyber operator exercising control over an enemy ship.Footnote 89 Questioning the relevance of the IHL rule against perfidy in the cyber context,Footnote 90 Christopher Bailey affirms that “a range of novel ruses” in cyberspace “can be analogized to acceptable past practices” of ruse in traditional conflict settings.Footnote 91 As previously introduced,Footnote 92 the two Tallinn Manuals offer several illustrations of IHL analogies, and one of these also relates to the rule against perfidy. Noting that “simply failing to identify oneself as a combatant is not perfidy”, the two Manuals then compare the situation of a “cyber attack in which the originator is concealed” with the more traditional situation of a “sniper attack in which the location of the attacker or identity of the sniper may never be known”.Footnote 93 As to State practice, accepting that a cyber operation can constitute an attack under Article 49 of Additional Protocol I to the Geneva Conventions,Footnote 94 the French Manuel de droit des opérations militaires declares that
l’altération des capacités de propagande de l’adversaire, notamment, le fait de rendre indisponible un site d’influence sur les réseaux sociaux par saturation ou déni de service distribué, ne saurait être caractérisée comme une attaque, par analogie avec le brouillage des communications radio ou d’émissions de télévision.Footnote 95
While the interpretive function of IHL analogies is prevailing in the literature and practice related to this domain of warfare, some scholarly works also illuminate their creative function. For instance, Alexi Franklin scrutinizes existing weapon treaties to identify the best model for a new cyber treaty.Footnote 96 Thinking about possible protective measures against the potentially devastating civilian impacts of cyber operations, Michael Schmitt mentions that
special protection for cyber infrastructure and functions could be crafted analogously to that presently existing for objects indispensable to the civilian population or for civil defence activities. Doing so would likely require adoption of new treaty law in the form of, for example, a further additional protocol to the Geneva Conventions.Footnote 97
In the same vein, Robin Geiss and Henning Lahmann write that
a de lege ferenda approach could be applied to … cyber installations [that are] similar to the objects currently listed in Article 56 of Additional Protocol I – the neutralisation or destruction of which would typically result in significant civilian impact that would outweigh the military benefits.Footnote 98
Example 3: Outer space warfare
In the London Declaration of December 2019, the North Atlantic Treaty Organization (NATO) formally recognized outer space as a fifth operational domain, after land, sea, air and cyber.Footnote 99 This new domain of warfare has attracted more attention over the years and has become a focal point in recent IHL discussions. Following the same pattern as for the emergence of cyberspace as a domain of warfare, outer space similarly challenges IHL’s existing legal framework. While the outer space domain also raises questions about the interaction between IHL and other international legal regimes (particularly international space law),Footnote 100 this article focuses exclusively on IHL-related issues.
IHL scholarship primarily addresses two key questions: first, the applicability of IHL to outer space (i.e., whether IHL applies to outer space military operations), and second, the application of the principles of the conduct of hostilities – namely distinction, proportionality and precaution – in the context of space warfare (i.e., how IHL applies to outer space conduct of hostilities). Through its interpretive function, analogical reasoning brings valuable insights into both questions and contributes to a better understanding of how IHL regulates outer space warfare. As with LAWS and cyber operations, IHL scholars tend to conceive of analogies as similarities of terms; they therefore employ analogical reasoning to extend the scope of application of existing IHL rules to military operations conducted in outer space, even though such operations would have been inconceivable at the time those rules were adopted. In this regard, it is enlightening to read in the introduction of the Woomera Manual on the International Law of Military Space Activities and Operations – although the chosen wording remains quite cautious – that it
focuses on those obligations of the law of armed conflict that may apply to space by way of direct treaty application, or otherwise through corresponding obligations contained within customary international law. Additionally, in determining this application, a limited use of the mechanism of analogy was applied to determine whether some particular rules of the law of armed conflict could apply to armed conflict in space.Footnote 101
More specifically, academic contributions relating to this fifth domain of warfare allow for four main observations. First, on a purely anecdotal note, the first type of analogies found in IHL scholarship are often descriptive or metaphorical rather than legal in nature: indeed, many essays begin by comparing potential real-world warfare scenarios in outer space to space fantasy narratives such as Star Wars.Footnote 102 Second, even though the language of analogy appears less prevalent in the academic literature on space warfare compared to previously examined topics, emphasis is frequently placed on IHL adaptabilityFootnote 103 – a quality to which analogical reasoning significantly contributesFootnote 104 – or on IHL translation for the space domain – which refers to the third cognitive step of analogical reasoning that is transfer.Footnote 105
Third, space warfare is often analogized at a very broad level with other domains of warfare, particularly cyber warfare, but also land, maritime or aerial warfare.Footnote 106 A significant number of authors refer either to cyber warfare scenarios or to State and expert discussions on cyber operations – especially the Tallinn Manuals – to support their views on space warfare.Footnote 107 Others draw connections between the necessary extension or adaptation of IHL for space warfare and previous developments in IHL through analogical reasoning, such as the evolution from land warfare to maritime warfare or aerial warfare.Footnote 108
Fourth, IHL scholarly works contain numerous instances of specific analogies in the context of space warfare. These analogies establish parallels between outer space situations and traditional warfare situations. For example, Steven van de Put and Anne-Rixt Siemensma consider the issue of military astronauts and their need for broader protection, analogizing combatant astronauts with shipwrecked soldiers.Footnote 109 Kubo Mačak examines the start of IHL applicability to outer space military activities and compares the launch of an anti-satellite weapon with the firing of intercontinental ballistic missiles.Footnote 110 Abdul Rehman Khan is interested in the proportionality analysis and suggests an analogy between dual-use satellites (especially satellites with some military functions hidden behind many civilian purposes) and human shields.Footnote 111 Dale Stephens and Cassandra Steers use several analogies, such as between dual-use objects in space and those on land, sea or air for the purposes of the principle of distinction, and between downing an attacking aircraft and disrupting satellite links for GNSS/GPS-linked drones and munitions in relation to the proportionality principle.Footnote 112
All these examples strongly suggest that analogies in their interpretive function are central to scholarly engagement with space warfare under IHL; however, it is worth recalling here that their interpretive function is not without prejudice to their creative function. Analogies also help design and shape new rules for space warfare. To take just one example, Idrovo Romo finds a useful analogical source in the IHL higher standard of imperative military necessity to protect cultural objects and concludes that, “[i]n case a new treaty is developed [for space warfare], the standard of imperative military necessity should be considered for any attack directed to space objects that are particularly vulnerable such as satellites”.Footnote 113
Beyond academic literature, States and the ICRC have not extensively elaborated on the underlying rationale for their positions regarding IHL applicability and application to outer space. As a result, their practice does not explicitly document the importance of analogical reasoning for IHL development in this domain.
Discussions within the Group of Governmental Experts on Further Practical Measures for the Prevention of an Arms Race in Outer Space, as well as within the newly established Open-Ended Working Group on the Prevention of an Arms Race in Outer Space in All Its Aspects, merely reveal a divide among States: some support IHL application in outer space, while others fear that such recognition could legitimize warfare in space.Footnote 114 No definitive conclusion about analogical reasoning can be deduced from these discussions. Similarly, State military manuals generally do not explicitly invoke analogies when addressing military operations in outer space during armed conflictFootnote 115 – except, perhaps, for the US Law of War Manual, which states that “the application of the law of war to activities in outer space is the same as its application to activities in other environments, such as the land, sea, air, or cyber domains”.Footnote 116
As for the ICRC’s official documentation, it primarily focuses on protecting civilians from the harmful consequences of military operations in space.Footnote 117 The new ICRC Commentary on Article 2 of GC IV only notes in passing that “[i]nternational humanitarian law, as well as other bodies of international law, would also apply to an [international] armed conflict occurring in outer space”.Footnote 118 More interestingly though, the new ICRC Commentary on Article 3 of GC IV seems to timidly draw an analogy between cross-border NIACs and NIACs in outer space for the purpose of IHL applicability, recognizing IHL applicability to outer space in a footnote to a paragraph addressing IHL applicability to cross-border NIACs.Footnote 119
This being said, the absence of known explicit references to analogical reasoning in both State and ICRC practice does not appear to contradict the argument made in this article. Rather, it seems to reflect the limited availability of practice on the topic (particularly from States) and the practical orientation of some existing documents, which does not invite their authors to elaborate on their legal methodology and reasoning.
Example 4: Non-international armed conflicts
In contrast to the three previous examples, NIACs do not, eo ipso, constitute a recent phenomenon requiring regulation by IHL. Moreover, the importance of analogical reasoning in the development of the law of NIAC is well established, almost to the point of being a truism. Many customary and conventional norms applicable to NIACs rely on analogies with the corresponding legal regime applicable to IACs;Footnote 120 as a result of this, as noted by Lizaveta Tarasevich in 2020, “[t]he norms governing NIACs have rarely developed specifically for … situations of internal conflicts – they rather developed by analogy to the rules regulating IACs where such extension was possible”.Footnote 121
Despite some progress, the law of NIAC is still widely regarded as the part of IHL that is most in need of further development. As some commentators indicate, it is the part of IHL which is, “at least as far as treaty rules are concerned, in the greatest need of new, more detailed and updated regulation”,Footnote 122 or in other words, it is an “urgent issue” that “cr[ies] out for regulation”.Footnote 123
Clearly, several key differences persist between the laws of IAC and NIAC – the former being more detailed, particularly regarding the status of individuals (combatant and prisoner of war (PoW) status), internment regimes, situations of occupation and environmental protection.Footnote 124 These persistent differences have long constituted resistance poles to the analogue extension from the law of IAC to the law of NIAC. However, the remaining gaps in the law of NIAC have been the subject of sustained debate since the beginning of the century – especially in the context of the global fight against terrorism and the rise of so-called transnational or cross-border armed conflicts, defined as armed conflicts opposing at least a State and an organized armed group, or two organized armed groups, and crossing at least one State border.Footnote 125 In such conflicts, States that operate extraterritorially cannot rely easily, or at all, on their own domestic law to fill the gaps in NIAC regulation. Thus, the limitations of the law of NIAC have become even more problematic. As Marco Sassòli underlines, “th[e] attraction for analogy really came up recently with the appearance of so-called transnational non-international armed conflicts”.Footnote 126
Indeed, contemporary IHL debates on the law of NIAC continue to draw explicit analogies with the law of IACFootnote 127 – although they now also touch upon some major historical differences between the two kinds of conflicts.Footnote 128 Academic scholarship offers several examples. For instance, the law of NIAC is silent on the legal basis, admissible grounds and review procedures for internment. Scholars have examined the merits of analogizing NIAC internment practices with either PoW internment under Geneva Convention III (GC III) or civilian internment under GC IV.Footnote 129 Similarly, on targeting, the law of NIAC provides very limited guidance on the definition and identification of fighters within an organized armed group – i.e., members of the group who are always considered lawful targets under IHL. Consequently, IHL literature explores the possibility of transferring the “membership” or the “belonging” approaches from the law of IAC to the law of NIAC. The “membership” approach defines fighters “on the basis of their membership to an armed group or to armed forces”, thus “using the same reasoning than for distinguishing combatants from civilians in IHL of IAC”.Footnote 130 The “belonging” approach refers to Article 4 of GC III, which provides that “prisoners of war … are persons belonging to one of the [described] category, who have fallen into the power of the enemy”.Footnote 131 Furthermore, the law of NIAC does not contain provisions relating to situations of occupation by organized armed groups, and nor does it impose obligations on these groups regarding environmental protection, prompting considerations of analogies with the occupation regimeFootnote 132 and environmental norms found in the law of IAC.Footnote 133
All these examples thus show that in today’s IHL academic debates, the law of IAC remains a starting point for discussions on the necessary development of the law of NIAC. However, unlike the three previous examples of LAWS, cyber and outer space, the relevant form of analogy here is a similarity of relations: the legal framework governing IACs does not apply to NIACs as such, but rather serves as a model for designing the new legal framework that ought to govern NIACs. Analogical proposals therefore rely on adaptations of IAC rules specifically tailored to the NIAC context. This fourth example illustrates the creative rather than interpretive function of analogical reasoning: in this context of ongoing evolutions in the law of NIAC, IHL analogies are employed not as a method for interpreting the lex lata but as a means for advancing de lege ferenda proposals. Contemporary analogical solutions for NIACs are generally forward-looking – analogizers draw inspiration from the law of IAC to formulate proposals but they do not usually claim that these proposals can be applied directly to NIACs, since such proposals have not yet become fully integrated into the law governing NIACs.
This being said, State practice provides contrary illustrations where analogies with the law of IAC were already considered as part of the lex lata – albeit with criticism from IHL experts. US practice is particularly illuminating in this regard. To mention one example, the United States initially classified its fight against Al-Qaeda as a new type of armed conflict (a third category in IHL classification of armed conflicts) that is an IAC against a transnational organized armed group, thereby privileging the analogy with traditional IACs rather than with classical NIACs.Footnote 134 Such classification appeared clearly in the 2007 version of the Commander’s Handbook on the Law of Naval Operations – which is curious, because this manual was published after the Hamdan decision delivered by the Supreme Court that marked a change in US legal position and its clear acceptance of the applicability of Article 3 common to the Geneva Conventions to the said armed conflict.Footnote 135 This handbook had a third section – after the sections on traditional IACs and NIACs – entitled “International Armed Conflict between Nation States and Non-State Actors”, which asserted:
Since 11 September 2001, a new type of armed conflict has emerged: international armed conflict between nation States and non-State actors. The Global War on Terror is an example of this new type of conflict. International armed conflict between nation States and non-State actors differs from international armed conflict in that it is not between two or more high contracting parties (e.g. nation States). It also differs from non-international armed conflict in that it is international in character.Footnote 136
According to the United States at the time, this new category – which seems to be based on an analogy with the traditional IAC classification – was thus part of IHL and constituted the lex lata, not a de lege ferenda proposal.
Example 5: Belligerent cooperation in international and non-international armed conflicts
Like the previous example, this fifth illustration does not introduce a phenomenon that is entirely new to IHL; instances of belligerent cooperation against a common enemy existed well before the beginning of this century. What is genuinely new, however, is the scale and diversity that this phenomenon has acquired since the beginning of the third millennium, especially in the context of NIACs. In such context, military assistance has been provided by a variety of actors. States have sometimes provided assistance independently – for example, France’s support to the G5 Sahel countries through Operation Barkhane, which ended in 2022Footnote 137 – or have formed coalitions to fight against organized armed groups. This includes the US-led international coalition which fought against Al-Qaeda and the Taliban forces in Afghanistan after the fall of the Taliban regime,Footnote 138 as well as the other US-led international coalition engaged against IS, notably in Syria and Iraq (the so-called Global Coalition against Daesh, with ninety partners in July 2026).Footnote 139 Additionally, belligerent cooperation in NIACs is not a prerogative reserved to States; for instance, the organized armed group Hezbollah provided support to the Syrian regime in 2013 when the latter was fighting against other armed groups.Footnote 140 Further, as already indicated in the introduction of this article, the ongoing IAC between Russia and Ukraine is a clear example that belligerent cooperation is also a highly topical issue in the context of contemporary IACs.
This type of belligerent cooperation (namely, military assistance) raises significant issues for IHL, particularly with respect to its personal scope of application. In such circumstances, it is necessary to determine which actor acquires the status of party to an armed conflict and is therefore bound to fully comply with the law of NIAC or IAC. However, the existing rules which determine IHL’s scope of application have not traditionally been designed to regulate belligerent cooperation; the rules governing the classification of armed conflicts focus primarily on belligerent opposition rather than collaboration. As a result, both IHL scholars and States have proposed frameworks aimed at regulating belligerent cooperation in NIACs and IACS – and these emerging approaches often rely on analogical reasoning.
Regarding NIACs, US practice refers to a new concept of “associated forces” to address belligerent cooperation between organized armed groups. This concept has been invoked to justify the State’s authority to use force and detain members of organized armed groups that operate alongside Al-Qaeda. According to US authorities, the notion draws on an analogical reasoning with the concept of “co-belligerency” traditionally associated with IACs. Indeed, in a 2009 memorandum submitted to the District Court for the District of Columbia, the US government explained that, although “[i]t is neither possible nor advisable … to identify … the precise characteristics of ‘associated forces’”, the United States may detain “individuals who, in analogous circumstances in a traditional international armed conflict between the armed forces of opposing governments, would be detainable under principles of co-belligerency”.Footnote 141 In adopting this approach, US authorities were inspired by the scholarly work of Curtis Bradley and Jack Goldsmith,Footnote 142 who notably affirm that
[t]errorist organizations that act as agents of al Qaeda, participate with al Qaeda in acts of war against the United States, systematically provide military resources to al Qaeda, or serve as fundamental communication links in the war against the United States, and perhaps those that systematically permit their buildings and safehouses to be used by al Qaeda in the war against the United States, are analogous to co-belligerents in a traditional war.Footnote 143
The concept of “associated forces” is thus the result of an analogy understood as a similarity of relations. US authorities did not extend the IAC notion of co-belligerency directly to NIACs; instead, they have consistently used a separate concept inspired by that notion but specifically reconfigured for the NIAC context.
Similarly, when examining the issue of participation in a pre-existing NIAC, the ICRC has employed analogical reasoning to develop its “support-based approach” (SBA).Footnote 144 While the Committee initially remained silent about the analogical foundation of this approach, it eventually acknowledged that the notion draws analogical inspiration from the existing concept of direct participation in hostilities (DPH), which addresses situations in which an individual participates in ongoing hostilities.Footnote 145 Indeed, at the 2018 Bruges Colloquium on the legal and operational challenges raised by contemporary NIACs, an ICRC representative highlighted that the “[SBA] is inspired by [DPH]” and that “[t]he concept of [DPH] has been adapted to cover acts, not of civilians, but of organised armed groups”.Footnote 146 These clarifications employ a traditional vocabulary for analogical reasoning (“inspired by”, “adapted to”).
Again, the analogy underlying the SBA refers to a similarity of relations rather than a similarity of terms. The DPH framework does not apply as such, nor is it extended to situations involving belligerent participation in a pre-existing NIAC. It would be incorrect to conclude that DPH applies by analogy to such situations, as although the SBA is inspired by an analogy with DPH, it constitutes a distinct legal solution, adapted to a different context – the concepts of DPH and SBA are thus closely related, but not identical. Participation by an individual in ongoing hostilities bears some resemblance to the participation of a belligerent in a pre-existing NIAC; therefore, the ICRC has relied on DPH when proposing the SBA.
In the present author’s view, both the US authorities and the ICRC seem to consider that their respective analogical solutions to regulate belligerent cooperation form part of the lex lata. The United States uses the concept of “associated forces” as though it was part of the existing IHL framework, and the ICRC likewise applies the SBA in its day-to-day practice and suggests a legal basis in contemporary IHL norms, noting that the SBA “helps clarify the contours of the notion of NIAC … [and] provides insight into how to interpret this notion in keeping with the logic of IHL”.Footnote 147 However, this author believes that the concept of “associated forces” and the SBA can only be characterized as lex ferenda: the law of NIAC does not provide a convincing legal basis from which such specific notions can be deduced, and current State practice is not general and consistent enough to accept a new IHL customary rule in NIACs.Footnote 148 This author is therefore of the opinion that these examples are better understood as de lege ferenda proposals illustrating the creative function of analogies. This divergence of views – between what both the United States and the ICRC seem to argue and what the present author thinks – is a welcome reminder of the caveat noted above: the boundary between the interpretation and the creation of legal norms, as well as between lex lata and lex ferenda, is not always straightforward.
A final remark should be made regarding this fifth example. As indicated in Example 4 concerning NIACs, IACs often remain the starting point for discussions concerning ongoing developments in the law of NIAC. In relation to Example 5, however, a counter-example – or perhaps an exception – to this general assertion emerges. Interestingly, several authors have proposed extending the SBA, which was originally developed by the ICRC for military assistance in the context of NIACs, to situations involving similar military assistance in IACs.Footnote 149 This form of analogical reasoning is a similarity of terms. The SBA is thus applied by analogy in the context of IACs: the participation of a belligerent in a pre-existing NIAC is considered sufficiently similar to the participation of a belligerent in a pre-existing IAC. Therefore, the legal solution suggested for the former – namely, the SBA – is extended as such to the latter, resulting in the application of the same legal framework to both situations. Thus, the original analogy with DPH, developed in the context of NIACs and subsequently extended to IACs, would be relevant for both NIACs and IACs.
These examples demonstrating the important use of analogies in the ongoing development of IHL do not come as a surprise. As previously explained in this same forum, analogical reasoning has already played a significant role in the historical development of IHL;Footnote 150 the present research findings align with this previous observation and reaffirm that analogies are critical for IHL’s overall development.
Naturally, IHL experts and stakeholders employ analogies for current IHL development because analogical thinking offers clear cognitive advantages. At a fundamental level, it provides a conceptual framework that helps avoid the daunting prospect of approaching new legal challenges with a blank slate.Footnote 151 However, this article seeks to emphasize and raise awareness of the limitations and potential risks associated with the extensive use of analogical reasoning in contemporary IHL discourses. These limitations and risks are the focus of the closing section of this article.
Limitations and risks of IHL analogies
Reasoning by analogy in the ongoing development of IHL necessarily involves two kinds of limitations. First, there is a set of limitations that are inherent to the structure of analogical reasoning and are thus also found in IHL when such reasoning is used. Second, IHL has its own principled structure which restricts the potential of analogies and confines them to clear boundaries. When these two kinds of limitations are not respected – i.e., when an analogizer decides to disregard analogical or/and IHL structure(s) – dangers arise for the integrity of this branch of international law. These dangers may lead either to an unjustified reduction in the protection afforded to victims of armed conflicts or, conversely, to an excessively protective regime that fails to account for the realities of warfare and thereby loses credibility in the eyes of belligerents.
Limitations related to analogical structure
Analogical reasoning imposes two main structural constraints that hinder the further development of IHL: the relationship between the analogical source and target, and the subjective dimension behind the cognitive process supporting analogical thinking. Each of these two structural constraints deserves additional explanation.
The source–target relationship
In any analogical reasoning, the target is intricately linked to the source, whose legal regime either applies to or inspires the framework developed for the target. This relationship between the target and the source inherently restricts legal innovation in three ways.
First, analogical thinking leads to an analysis of the target through the lens of the source and does not really consider the target’s unique characteristics.Footnote 152 As Robin Geiss has rightly illustrated in a different context,
[i]t is like being asked to build a BMW, but to build it with the parts of a Mercedes and a Volkswagen. These are all great carmakers, but when you combine these parts, you will have constructed a Bmcedeswagen, and that might even look halfway decent but it’s not going to be a BMW, and the engine is not going to run smoothly.Footnote 153
This metaphor highlights that, through an analogical reasoning, the comprehension of the target is necessarily limited to what its relationship with the source reveals. New battlefield scenarios are understood through the prism of familiar ones; for example, LAWS are analyzed in relation to traditional weapons; cyber and outer space warfare through the lens of classical land, maritime or aerial domains; NIACs through the framework of IACs; and belligerent cooperation in armed conflicts through the definition and criteria of co-belligerency or DPH. Such analogical perspectives constrain the analytical process, as these emerging realities are viewed through the window of established ones. As An Hertogen has insightfully underscored, “when researchers become wedded to the paradigms that analogies provide, these analogies can limit the course of research”.Footnote 154
Second, and in line with the first limitation, analogies interfere with the ability to fully grasp and conceptualize the novelty of the target. The source is rooted in the past, and the target is assessed in relation to it. While analogical reasoning may foster creativity, it simultaneously restricts it by discouraging “out-of-the-box” thinking.Footnote 155 How can one conceptualize the new through the lens of the old? Analogical reasoning does not allow for a comprehensive exploration of all the possibilities for IHL development in response to novel phenomena in warfare; for instance, it fails to capture the unfamiliar and novel dimensions of LAWS, cyber/outer space conflicts, contemporary NIACs, and belligerent cooperation in both IACs and NIACs. It is highly desirable for IHL to address these dimensions, as although they may not alter the nature of human suffering on the battlefield, they have the potential to amplify it to an unprecedented degree owing to their scale and rate of expansion.
Third, the source serves as the reference point for reasoning, but time can affect the source in two ways, introducing uncertainty into the legal solutions developed for the target. First, the chosen source and its legal regime may themselves evolve over time, necessitating a reassessment of the analogy with the target, and second, the analogizer’s perspective may shift over time, leading to changes in the choice of source for the best analogy.Footnote 156 Indeed, as noted by Véronique Champeil-Desplats, “une analogie peut ainsi toujours être remplacée par une autre estimée plus pertinente ou adéquate pour résoudre un cas”.Footnote 157 Thus, to illustrate this point, while the “weapon analogy” may currently be seen as the most suitable one for LAWS, future developments – such as the deployment of LAWS on the battlefield – may render this analogy obsolete and prompt the adoption of new ones.
The subjective dimension of the cognitive process
Analogical reasoning intrinsically involves a subjective component, shaped by the analogizer. During the retrieval phase, the analogizer selects one or several sources from memory, a choice influenced by their informational background and prior experiences.Footnote 158 Furthermore, both the retrieval and the mapping steps require value-laden judgements, as the analogizer pursues specific objectives: in retrieving a source, they make a choice between multiple options, and in mapping the target and the source, they determine the criterion or criteria for comparison.Footnote 159 These two layers of choice provide a clear subjective input into the analogical process. The unavoidable subjectivity of analogical reasoning thus constitutes a clear limitation for the ongoing development of IHL, and such development will be constrained by the analogizer’s expertise, knowledge base and intended goals.
These observations hold true regardless of whether the analogizer is an individual, such as a scholar, or a collective entity, such as the ICRC or a United Nations working group. Such collective bodies are, ultimately, composed of representatives – that is, groups of individuals. As a result, although the pool of past experiences and specific objectives may be wider within a group, thereby expanding the range of potential analogical solutions, this does not eliminate the subjective dimension inherent to the analogical process. This subjective dimension persists because the analogical process derives from the human nature of its participants.
The subjective character of analogical reasoning calls for caution when employing analogies for the ongoing development of IHL. Reasonable people may reasonably disagree, which explains why the relevance of particular analogies remains contested in IHL literature concerning LAWS, cyber/outer space warfare, contemporary NIACs and belligerent cooperation in armed conflicts.
Limitations related to IHL’s structure
Before addressing specific limitations related to IHL’s structure, it is important to recall that IHL is a branch of international law and that therefore, general constraints on analogical reasoning under international law also apply to IHL; for instance, analogical outcomes must not contradict jus cogens norms, such as the prohibition of torture.Footnote 160 While the reader should not lose sight of these general limitations, the present article focuses on those specific to the internal structure of IHL.
IHL is organized around a set of fundamental principles which must be considered when using analogies in this legal field. Chief among these are the principles of humanity and necessity. IHL norms are built upon a delicate balance between these two principles,Footnote 161 but this balance is not always embedded within individual norms; it sometimes emerges from the interplay between several provisions.Footnote 162 Whether inherent to a single norm or resulting from a constellation of norms, the equilibrium between humanity and necessity must be preserved while analogizing in IHL.Footnote 163 This can become complex when analogical reasoning is applied to norms that are part of a broader normative framework through which humanity and necessity are balanced. In all cases, when someone uses analogies in IHL, as for LAWS, cyber/outer space, contemporary NIACs, or belligerent cooperation in armed conflicts, such analogical reasoning must not shift this foundational balance in favour of either humanitarian or military considerations.
The principle of equality of belligerents constitutes another important “bedrock principle” of IHL.Footnote 164 On a very basic understanding of the principle, it requires that the same rules – i.e., obligations and rights – apply to all belligerents in an armed conflict regardless of the reasons and political motivations behind their engagement.Footnote 165 This principle imposes a clear limitation on the analogical process: any suggested analogical solution must apply to all belligerent parties. In the context of an IAC, a State cannot invoke an analogical reasoning to expand its rights while denying the same expansion to its State adversary. The same applies – perhaps even more critically – in NIACs: any analogical solution must be viable for both the State party and the non-State party. This limitation is thus particularly relevant when NIACs are analogized with IACs; in such circumstances, it is crucial to verify whether the proposed analogical solution inspired by the law of IAC is realistically applicable to and by organized armed groups.Footnote 166
Additionally, beyond its foundational principles, IHL possesses other structural characteristics that further constrain analogical thinking. First, IHL is very anthropocentric in nature; IHL rules were and still are designed by and for human beings, and their language reflects this orientation.Footnote 167 This human-centred focus complicates analogical reasoning in contexts involving a less human-oriented focus, particularly involving entities or objects that do not fit neatly into existing categories, such as LAWS, which seem to occupy a conceptual space between weapons and humans (fighting in an armed conflict).Footnote 168 While these weapons systems necessarily maintain a dual link with human beings through the decision to use them on the battlefield and the consequences for potential human victims, they possess characteristics that are ordinarily unique to human beings, which explains a certain discomfort under IHL towards them.
Second, certain rules in international law explicitly prohibit analogical thinking,Footnote 169 and one such rule indirectly affects IHL. IHL consists of a corpus of primary norms defining conduct in wartime, and violations of certain of these norms may give rise to individual criminal responsibility according to international criminal law (ICL).Footnote 170 In ICL – at least in the era of the International Criminal Court (ICC) – as in European domestic law systems,Footnote 171 analogical reasoning that disadvantages the accused is prohibited. Article 22(2) of the Rome Statute of the ICC provides that “[t]he definition of a crime shall be strictly construed and shall not be extended by analogy”.Footnote 172 It is accepted that this rule only prohibits analogies which create new norms de lege ferenda (creative function of analogies); however, it does not preclude the analogical interpretation and application of the lex lata (interpretive function of analogies).Footnote 173 Consequently, ICL limits the reach of certain IHL analogies (though this appears entirely logical as these analogies concern hypothetical norms that have not yet attained legal status) unless they evolve into customary law. The ICC would not prosecute an individual on the basis of a proposed innovative rule related to LAWS, cyber/outer space, contemporary NIACs, or belligerent cooperation in armed conflicts that currently has no legal status other than that of a mere analogical proposal.
Risks related to various alterations of analogical or IHL structure(s)
The important use of analogies in the ongoing development of IHL carries the risk of disrespect for the structural constraints presented in previous subsections of this article. More specifically, dangers stem from alteration(s) of either the structure of analogical reasoning or the foundational organization of IHL. Unfortunately, these risks are not just theoretical. It has already been noted in this article that the United States introduced IHL concepts such as an “international armed conflict between nation States and non-State actors”Footnote 174 or “associated forces”Footnote 175 – which are based on questionable analogical reasoning – specifically aimed at expanding its authority to target and detain individuals in its armed conflicts with transnational armed groups.
On the one hand, analogizers may distort the structure of analogical reasoning, selectively engage with its steps and only go for what they like in the analogical process. They may (unintentionally or intentionally) adopt a very partial understanding of the analogical process, seeking “all of the advantages of [a specific] analogy with none of its disadvantages”.Footnote 176 During the mapping step, they may (purposefully) overlook differences between the source and the target, focusing only on some (superficial) similarities.Footnote 177 For instance, as mentioned earlier in this article, the US concept of “associated forces” – which refers to organized armed groups fighting alongside Al-Qaeda against this State – is based on an analogy with the situation of “co-belligerency” regulated under the law of IAC.Footnote 178 However, as this author has argued elsewhere,Footnote 179 this analogy is not valid due to critical dissimilarities that the United States has disregarded. In addition, in the transfer phase, analogizers may also adopt a selective approach and only extend to the target what they want from the source.Footnote 180
On the other hand, analogizers may alter the structure of IHL itself when employing analogical reasoning. Examples that immediately come to mind are analogies which either cause an imbalance between the principles of necessity and humanity or disrespect the principle of equality of belligerents. These dangers are especially pronounced when analogizing modern NIACs with IACs. As Marco Sassòli has noted, while the analogy between IACs and NIACs was initially suggested to advance humanitarian concerns, it was later used to justify permissive measures,Footnote 181 thereby unduly privileging military necessity over humanity. This illustration also underscores the difficulty of anticipating the long-term consequences – including unintended ones – of suggested analogies “in shaping thought and, therefore, society”.Footnote 182
Concluding thoughts
Amid evolving battlefields, IHL strives to adapt and remain connected to real-world realities. Analogical reasoning supports this evolution in two ways. First, it serves as an interpretive method for existing norms, enabling the extension of their scope of application to new warfare situations that are comparable to those which were initially envisaged. Contemporary literature and practice on LAWS, cyber operations and outer space illustrate the important use of analogical reasoning to assess the applicability and application of the current IHL framework to modern battlefield challenges. Second, analogical thinking contributes to the formulation of new legal norms when the existing IHL framework proves indeterminate. Relevant scholarship shows that proposals for developing the law of NIAC often draw inspiration from the law of IAC. Similarly, suggestions for a better understanding of belligerent cooperation in armed conflicts rely analogously on other situations deemed comparable and already governed by law, such as DPH. This documented dual role leaves no doubt that analogical reasoning plays a central role in IHL’s ongoing development.
However, the considerable potential of analogical reasoning in IHL is accompanied by significant limitations and risks. These constraints pertain not only to the structure of analogical reasoning itself, but also to the normative architecture of IHL. Whenever these limitations are disregarded, IHL’s integrity and credibility are placed in jeopardy. It is therefore incumbent upon IHL experts and stakeholders to maintain a vigilant stance; as rightly stated by Fernando Lusa Bordin, we must keep “a watchful eye … when analogy is used in codification and progressive development”.Footnote 183 If this article achieves but one objective, it is hopefully to raise awareness of the potential risks associated with the important use of analogies. Analogies are a great tool for development, but IHL experts and stakeholders must pay close attention to their everyday use and exercise careful monitoring to report any misuse of analogical reasoning.
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