It is trite to say that warfare has existed almost since the beginning of humankind, and that the laws of war have developed from centuries of practice on the battlefield into a quite extensive treaty regime.Footnote ¹ In this regard, the jus in bello (international humanitarian law / the law of armed conflict) has deep historical roots and constitutes amongst the oldest branches of international law.Footnote ²

By contrast, wars have often been significant drivers of technological advancement, whose development has allowed for new and innovative ways in which to conduct activities on the battlefield. The technology and complexity of warfare continues to evolve, sometimes quite rapidly, giving rise to interesting questions as to how to apply these well-established legal principles in modern times. There certainly are challenges to be met in attempting to reconcile law that has emerged primarily over the nineteenth and twentieth centuries with the realities of twenty-first century technology and combat strategy.

Indeed, the principles of international humanitarian law have traditionally been regarded as being ‘one war too late’ or, as Emily Crawford puts it in her recently published book, ‘one war behind reality’.Footnote ³ Similar to several other areas of law, this reflects the ‘reactive’ nature of international law, which typically develops only over a period of time rather than very rapidly. Indeed, in most cases, the ‘creation’ of new binding rules (or the adaptation of existing international law rules) generally arises in response to certain, perhaps unforeseen, situations, rather than beforehand.

The reality is that much of the codification of international law, particularly, as noted in this book, in areas where technology moves forward very quickly, is (and can only be) responsive in approach. This certainly extends to areas where humans are engaged in conflict – as demonstrated not only in the area of international humanitarian law, but also with respect to international criminal law and international human rights law.

It is this dilemma that Crawford's excellent book seeks to address. It focuses on one of the fundamental principles of the laws of war – the legal protections afforded to civilians during warfare – and applies this within the context of modern armed conflict. This leads to some difficult and, at times, uncertain conclusions as to what the correct legal position is.

The law relating to civilian participation in hostilities is inextricably linked to the principle of distinction, described by Crawford as a ‘fulcrum’ of the law of armed conflict.Footnote ⁴ As well as representing customary international law, the principle is reflected in many of the jus in bello treaties.Footnote ⁵ In the Legality of the Threat or Use of Nuclear Weapons Advisory Opinion, the International Court of Justice stated that one of the cardinal principles of the jus in bello involves:Footnote ⁶

Distinction therefore requires that parties to an armed conflict distinguish between civilians / civilian objects and combatants / military objects. In its formative phase, the application of the principle was relatively straightforward, and based on the ‘assumption’ that the distinction could be made ‘clearly and easily’.Footnote ⁷ However, as Crawford suggests, the evolution of armed conflict, both in terms of strategy but also in its use of technology, has made this a far more difficult and, at times, almost impossible obligation with which to comply. Yet, the underlying rule of law has not itself changed or been significantly adapted to match the shifting factual matrices in which it is increasingly to be applied.

The distinction between what is ‘civilian’ and what is not is, of course, highly important. A failure to comply with the principle potentially renders the relevant decision maker in breach of the requisite standards, which might lead to international (or national) criminal responsibility. It also reflects what Crawford refers to as the ‘dyad of immunity and targeting’:Footnote ⁸ a combatant retains certain ‘benefits’ under the jus in bello but remains a target, whilst civilians – ‘all those persons who are not combatants’Footnote ⁹ – are immune from being targeted unless they directly participate in hostilities. When a civilian is found to be participating in this way, he / she loses that immunity, but does not at the same time acquire the corresponding combatant benefits. Naturally, this has grave impacts upon the legal position of the (former) civilian.

It is in this context that Crawford's book proceeds. It begins by discussing in detail the development of the relevant law relating to civilian participation in armed conflicts. She recognizes that, despite its evolution and the protections given to civilians in the form of the targeting immunity noted above, ‘civilians have taken and continue to take direct part in hostilities’,Footnote ¹⁰ and are doing so in ‘manifold ways, and in a number of direct and indirect ways’.Footnote ¹¹ Yet, the rules are such that the issue as to how civilians lose this immunity has, in Crawford's opinion, ‘remained, until recently, notably unexamined’,Footnote ¹² and the concepts of ‘civilian’, ‘civilian immunity’ and ‘civilian loss of immunity’ have largely been ‘sidelined’.Footnote ¹³ Crawford therefore seeks to unpick the various legal issues that arise.

Before she can focus on the complexities that stem from the context of modern warfare, Crawford describes the law relating to civilian participation in armed conflict – including a discussion of the 1949 Geneva Conventions and the 1977 Additional Protocols – as well as the notion of direct participation in hostilities (which she refers to as ‘DPH’). She regards DPH as an ‘exception’ to civilian immunityFootnote ¹⁴ that only became codified in the 1977 Additional Protocols, although its scope is still not particularly clear.

After reviewing national case law from Israel, the United States and Germany, jurisprudence from various of the international mechanisms of criminal justice, and some other sources (including the Harvard Manual),Footnote ¹⁵ she agrees with the view that a determination of whether or not a civilian has directly participated should best be undertaken on a case-by-case basis.Footnote ¹⁶ Naturally, this may make sense in many situations, but it may also render uncertain the true legal position in some circumstances, a fact that becomes even more relevant given the various current ‘challenges’ that Crawford proceeds to examine in the second part of the book.

The first of the challenges arises from the practice of ‘targeted killing’, the contemporary meaning of which is described as ‘the deliberate and premeditated killing of specific persons’.Footnote ¹⁷ Crawford points out the difficulties raised by the justification of such acts (by countries such as Israel and the United States) as lawful acts of self-defence. She describes this as a ‘jus ad bellum / jus in bello conflation’Footnote ¹⁸ arising from a blurring of concepts from these two distinct legal regimes, while adding that the practice might also incorporate issues relating to international human rights law. All this means, in Crawford's opinion, that there is confusion as to what the applicable law(s) might be, particularly if such actions are directed against so-called ‘terrorists’, in respect of whom the jus in bello might often not apply, due to the absence of an armed conflict. A consequence of this is that the rights of the targeted person may be unclear, as is the legality of the act of targeted killing itself.

Crawford then moves on to discuss so-called ‘remote warfare’, which encompasses, among other things, the use of drones and cyber-related activities. Weapons-related technology, as well as the advent of different types of (non-state actor) participants in armed conflict, has meant that the traditional mode of warfare no longer represents the absolute norm. We have increasingly witnessed the incorporation of sophisticated weapons related systems, including cyber technology, remote controlled weapons systems such as drones, robotics and satellites, to help to fight wars.

It might from one perspective be argued that the advent of these forms of weapons-related technology offers some ‘opportunities’. One such opportunity that deserves further consideration is that, to the extent that it allows for greater target selectivity and accuracy, it might actually have the capacity to both minimize casualties during armed conflict and reduce the probability of collateral civilian damage. Both of these consequences would, of course, be welcome and in keeping with the fundamental jus in bello principles, including the principle of distinction; so much so that one might be tempted at first instance to argue that it therefore obligates a combatant to use this technology where available during the conduct of armed conflict.

However, that is perhaps too simplistic and necessitates a more rigorous consideration. Notwithstanding benefits flowing from possible greater target selectivity, the utilization of this technology at the same time presents very real and significant challenges to the application of existing legal frameworks, in the absence of further adaptation and addition, and compliance with the principle of distinction thus remains complicated. The changing nature of armed conflict means that the lines between lawful targets and protected objects may become increasingly blurred, as might the distinction between civilians and combatants, due primarily to the growing involvement of civilians and civilian activities during armed conflicts.Footnote ¹⁹ The selection process involved in the distinction requirement has become more difficult, so that enhanced target accuracy will not necessarily give rise to greater compliance.

Indeed, since civilians can sometimes play a direct part in hostilities, some commentators suggest that it is perhaps now more accurate to state that the customary principle of distinction requires a differentiation to be made between ‘combatants, legal or otherwise,Footnote ²⁰ and those civilians who do not take a direct part in hostilities’.Footnote ²¹

As Judge Lachs of the International Court of Justice has observed:Footnote ²²

Along the same lines, Crawford observes that what she refers to as the ‘increasing digitization of conflict’Footnote ²³ has significant impacts from a legal perspective. One of these involves the ‘potential repercussions in civilian participation’ in such strategies of warfare.Footnote ²⁴ She describes the activities of the CIA, which runs the US drone program but is not a formal part of its armed forces. This raises the question of whether those CIA employees working on the program should be considered in law as civilians taking DPH. She concludes that these circumstances give rise to ‘bad precedent’ and that, whilst trying to kill so-called ‘unprivileged belligerents’ through the drone program, a new subset of similarly unprivileged belligerents may have been created among those same CIA operativesFootnote ²⁵ This leads her to ask a difficult question: ‘What is to stop other States targeting [these CIA operatives] in their cubicles in Langley, or even in their homes?’ In essence, her analysis leads to the rather startling possibility that they too can be targeted under the laws of war without any immunity, a conclusion that reasonably flows from her analysis.

By contrast, Crawford concludes that, when it comes to so-called cyber-attacks, most of these are undertaken by civilians who fall short of having engaged in DPH. As a consequence, she refers to the assertion of David Turns, that civilians engaging in cyber warfare are doing so ‘with impunity’.Footnote ²⁶ It is not clear without further consideration whether this analysis is entirely correct, thus further highlighting the uncertainties associated with attempts to apply existing principles to more modern phenomena like cyber-attacks, which increasingly challenge the traditional principles of what constitutes an armed conflict and whether, indeed, it (still) requires some aspect of kinetic force.

Crawford next considers another challenge, albeit one that is not necessarily new. She discusses the legal status of Private Military and Security Contractors (PMSCs) and, after extensive analysis, suggests that the vast majority of PMSCs should be regarded as civilians (the other ‘choices’ in her analysis are combatants or mercenaries). This, however, does not simplify the position since, as Crawford concludes, there are considerable difficulties in determining when PMSCs might be engaged in DPH. The uncertainty is all the more worrying given the advent of a number of large PMSC companies offering extensive services, which has led to the significant increase in the use of PMSCs in combat zones in recent years.

A more nuanced policy driven discussion follows in relation to the issue of high level criminal armed activities. Crawford poses the question as to whether such violence – for example as currently practised by the drug cartels in Mexico – should be considered as an armed conflict (non-international). Of course various of the jus in bello instruments limit those circumstances where a non-international armed conflict might be said to exist, but the extraordinary ‘military’ capacities of these groups, and the high rate of deaths associated with their activities, certainly may appear to be ‘either indistinguishable from warfare or else intricately connected to existing warfare’.Footnote ²⁷ Nonetheless, Crawford argues that such activities should remain outside of the sphere of international humanitarian law, although other areas of international law may be applicable, and there is clearly a need for tighter domestic regulation in respect of such activities.

Having considered these various challenges, Crawford then discusses what she believes to be the appropriate way forward. She suggests that there exists a lack of enthusiasm amongst states for the conclusion of any new comprehensive jus in bello treaty, instead recognizing the ‘remarkable proliferation’ of so-called soft law instruments in the area of international humanitarian law over the past 25 years. This tendency is not limited to the regulation of armed conflict but, notwithstanding its potential for flexibility and a ‘sense of ownership’ over the rules, it is clear that there are several shortcomings with this if it is to be regarded in practice as the only possible approach.Footnote ²⁸ As Crawford concludes, non-binding instruments are not a ‘panacea’ for all the problems associated with important aspects of international law.Footnote ²⁹

In the end, Crawford recognizes that, what is also lacking is a clear comprehension of the reasons behind why some categories of persons retain protections during armed conflict and others do not. She is undoubtedly correct in arguing the need for clearer and better definitions of ‘civilians’ and ‘combatants’. Given her extensive knowledge of the issues, it would have been very useful if she had offered her own thoughts on these in the book. She also believes that there continues to exist a lack of a clear understanding of the complexities associated with the concept of DPH, and that consensus on the issue is vital in order to protect one of the fundamental principles of international humanitarian law.

Overall, this is a very well written and researched book which raises difficult and thought-provoking questions. For perhaps understandable reasons, it is unable to offer definitive answers to some of these, and therefore represents an excellent platform upon which further research will be necessary. In this regard, it will appeal to students, practitioners, military personnel and governments, as they continue to grapple with the increasing complexity and constantly changing nature of warfare.