1.1 Background and Purpose
The question posed and answered in this book is: When may military forces1 use force during armed conflict? In order to focus the book the decision has been made to limit this question to the use of force against persons. Operationally, this is determined by the rules of engagement (roe), and the focus here is on nato roe. Legally, the answer is not so simple. Although the law of armed conflict (loac) is central to the regulation of the use of force during armed conflict, it is not the only applicable law. In particular, self-defence still applies. As a result, this book aims to tackle the relationship between loac and self-defence, and nato roe and self-defence. In doing so, answers will be sought to why there is a tendency among military forces to rely so heavily on self-defence during armed conflict, and how loac and roe are best applied in operations where the opponents cannot be easily distinguished from the civilian population.
For those tasked with carrying out military orders, the most important questions are: “What are we authorised to do? What will we be punished for doing or not doing? When and against whom can we use lethal force?” Rather than academic discussions setting out complex criteria which lawyers struggle to agree upon, military forces need, and deserve, clear answers. When the operational realities are complex, military forces should be given clear rules and guidance on when they may use force. It is precisely in complex situations, however, that following the rules is often difficult. In addition, military operations are likely to be subject to further political and operational restrictions to ensure respect for both the law and political and operational sensitivities. This complex picture makes it difficult for military forces to know exactly when they are permitted to use force, and it may be hard to distinguish legal requirements from other mission-specific limitations. This book will therefore analyse what the nato ‘use of force’ concepts authorise, what is required by applicable law, and how the operational tools reflect and ensure compliance with the legal requirements.
The main sources for the ‘use of force’ directions for military forces participating in a nato operation are the roe for the operation. roe are means of exercising political and operational control over military forces. They are designed to help ensure that military forces act in a manner that is both lawful and supports the political purpose and operational considerations of the mission. In nato, roe are developed from a standardised set of roe set out in the Military Committee Decision (MC) 362/1 NATO Rules of Engagement. They determine when, where, how and against whom force may be used during nato2 military operations and consist of both permissions for, and restrictions on, the use of force and other provocative actions. Although the focus is on nato roe, the underlying principles apply to all use of force during armed conflict; nato roe are merely an operational reality used here to shed light on questions concerning the application of law to the use of force by military forces during armed conflict.
roe are political restraints on the otherwise lawful use of force.3 The use of force against another person must have a clear legal authority in order not to be arbitrary.4 As a result, a central theme of this book is the legal principle that no person may be arbitrarily deprived of his or her life. All use of force must have a clear legal justification, and roe authorising the use of force should therefore have a clear legal authority. As will be further explained throughout the book, this means that nato roe cannot authorise force that is not permitted by applicable law, which during armed conflict primarily is loac.5 This should influence both the formulation and interpretation of the roe. If there is a need for roe authorising the use of force in connection with activities outside the ambit of hostilities and therefore not regulated by loac, inter alia, because it relates to crime rather than armed conflict, the legal authority for such use of force must be found elsewhere. For instance, if applicable, national law enforcement legislation may provide the necessary legal basis for using force. Importantly, nato roe does not deal with the use of force in self-defence as this is left for the respective nations to define.
Although the prohibition on arbitrary deprivation of life is today related to the human right to life, the idea that people cannot be killed without a proper reason is considerably older than modern human rights law, and its application to situations of armed conflict is uncontroversial.6 There are four general exceptions to this prohibition: the use of defensive force; the use of force to effect a lawful arrest or prevent the escape of a detained person; the use of force to quell a riot; and the use of force amounting to lawful acts of war.7 In armed conflict operations, the most relevant exceptions are the use of force amounting to lawful acts of war and self-defence. Although loac is the primary legal basis, situations may arise where loac does not provide the necessary authority, for instance, because the imminent threat does not amount to direct participation in hostilities, in which case self-defence may be relied upon.
This relationship between loac and self-defence is a running theme in the book. Why does military forces claim to rely on self-defence when loac provides sufficient legal authority? As will be explained, there is a tendency among nato forces to refer to all types of reactive or defensive force as ‘self-defence’, regardless of the applicable legal authority. In other words, it appears that an operational concept of ‘self-defence’ has developed, amongst others as a result of the policy that any use of force not authorised by roe must be self-defence. This causes unhelpful confusion concerning the applicable legal requirements for such defensive force. Which rules apply? Are the limitations imposed by necessity and proportionality sufficient to ensure compliance with loac? Although the legal concept of self-defence is important, loac is the primary legal regime for the use of force against lawful targets. This includes situations where the opponents are attacking or about to attack nato forces. The better approach would therefore be to separate the use of force in response to such attacks, based on loac, from the legal concepts of use of force in self-defence. In the meantime, it is important to understand the contents and implications of the operational self-defence concept.
loac requires that force is only directed at the persons who may legally be considered lawful targets. In order to comply with this rule, it is necessary to distinguish such persons from protected civilians. This can be particularly difficult when the opposing forces fail to distinguish themselves by wearing uniforms, for instance. Nonetheless, the roe authorising the use of force against persons must somehow designate who those persons are, in a manner that is possible to apply in practice. The legal and operational requirements for identifying opposing forces are therefore central to this book. Although this problem of facing opponents who do not wear uniforms is most prevalent in non-international armed conflicts, it is equally applicable to international armed conflicts. nato forces may, inter alia, face members of the civilian population who decide to resist military forces by forceful means, or conventional forces operating in an unconventional manner (so-called ‘hybrid warfare’8).
The operational aspect introduced by nato roe raises unique challenges due to nato’s multinational nature. As will be further explained in Section 1.4, 29 States entails 29 different versions of self-defence, 29 interpretations of international law, and last but not least, a wide range of international legal obligations. As a result, there is no uniform ‘nato approach’ to the law regulating the use of force authorised by nato roe or how the law should be applied.
The combination of complex ‘use of force’ categories and differing views on the applicable law may result in uncertainty regarding the scope of application of the roe. Such uncertainty is both unhelpful and undesirable, and the aim of this book is therefore to paint a clearer picture of the potential legal room for manoeuvre military forces have during armed conflict, through the lense of nato roe. This will be done by: providing a detailed examination of nato roe and the use of force categories in nato roe doctrine; explaining the need for a clear legal authority for the use of force and what this entails for roe; setting out what the relevant legal rules are and how they should be applied during armed conflict; examining the relationship between applicable law, and between self-defence, which is not regulated by nato roe, and roe based primarily on loac; and finally, by examining the connects and disconnects between the nato roe use of force categories and relevant law. The hope is to contribute towards enhanced clarity in an area inherently prone to uncertainty; namely the ‘fog of war’.9
1.2 nato Rules of Engagement
According to the nato roe doctrine, MC 362/1, nato roe are: “[d]irectives to military forces that define the circumstances, conditions, degree, and manner in which force, or actions which might be construed as provocative, may be applied.”10 While the definition and understanding of nato roe will be examined in detail in Chapter 2, some examples will be provided here in order to visualise the topic.
Use of all illuminants or illumination systems is authorized.11
Use of Riot Control Agents where necessary for purposes of mission execution is authorized, but only where such use is not a method of warfare.12
Use of non-deadly force to prevent the taking possession of or destruction of water facilities is authorised.13
Use of minimum force to prevent the taking of possession or destruction of radio tower is authorised.14
Attack against desig forces or individuals who demonstrate hostile intent (not constituting an imminent attack) against nato forces is authorised.15
Attack against desig forces or individuals who commit or directly contribute to a hostile act (not constituting an actual attack) is authorised.16
desig means to designate, and suggests that the roe drafters may provide further detail. The ‘use of force’ categories will be examined in Chapter 3.
1.3 Scope
1.3.1 Focus on the Use of Force against Persons during Armed Conflict
As mentioned above, as a result of the interest in the relationship between loac, roe and self-defence, this book is only dealing with nato roe for operations involving participation in armed conflict, and only the use of force against persons and not objects. Furthermore, the focus is on the use of force, which excludes detailed analysis of the nato roe regulating the use of provocative actions not involving the use of force.
In loac, there are two general categories of armed conflicts: international armed conflicts (iacs) and non-international armed conflicts (niacs).17 iacs include both armed conflicts involving two or more States and the occupation of one State by another.18 The threshold of iacs is relatively low.19 While the jus ad bellum regulates the initial recourse to force, it contains little detail on the conduct of hostilities. This is mainly found in loac. As a result, it is “logical and in conformity with the humanitarian purpose of the Conventions that there be no requirement of a specific level of intensity of violence to trigger an international armed conflict.”20 The test set out in loac is a factual one; an iac will exist when one or more States have recourse to armed force against another State,21 regardless of the recognition by one or both parties of a state of ‘war’.22 Occupation is also classified as an iac.23 As explained in the 2016 Commentary to Common Article 2, an iac occurs “when one or more States have recourse to armed force against another State, regardless of the reasons for or the intensity of the confrontation.”24
iacs may take place on the territories of both or all involved States, but may also occur within one State. Examples of the latter include armed conflicts where non-State forces opposing the State are fighting on behalf of another State, or where State A conducts out of area operations in State B, without State B being able to attack State A’s territory, as was the case of the nato campaign against Libya in 2011.
niacs include all armed conflicts not of an international character.25 The armed conflict may take place between a State and a group within that State; between a State and a group in another State, or between two or more groups.26 The threshold for finding that a niac is taking place and international law applies is higher than for iacs, requiring a higher degree of intensity.27 This is because States have retained greater liberty to use force within their own territory to deal with internal disturbance under national, rather than international, law. The accepted threshold for niacs is set forth in Article 1(2) of Additional Protocol II, although it is generally considered applicable beyond the limited scope of that treaty, at least where the conflict takes place within a State.28 A negative definition, it emphasises that “situations of internal disturbances and tensions, such as riots, isolated and sporadic acts of violence and other acts of a similar nature”29 are not armed conflicts. Such situations will in many States be dealt with by law enforcement officers, albeit possibly supported by military forces. Where the situation has escalated beyond internal disturbances and tensions, it will rise to the level of a niac to which the treaty rules and, more importantly, customary rules for such conflicts apply. Depending on the degree of control over territory, the conflict will either be regulated by AP II30 (if ratified) or Common Article 3.31 niacs within a State are also particularly likely to see interaction between loac and international human rights law (ihrl), because the conflict is occurring within the State’s jurisdiction.32 Finally, although AP I provides in Article 1(4) that certain niacs involving a fight for self-determination should be regulated as if they were international, this rule has little practical importance.33
In addition to the traditional civil war type niacs, niacs may also occur across international borders. iacs require State parties on both sides of the conflict, so if one or both sides is a non-State actor, the conflict must be classified as non-international, even if it is transnational. According to AP II Article 1, that protocol only applies to conflicts occurring within the territory of the State.34 The only provision in the Geneva Conventions applicable to transnational niacs is therefore Common Article 3. As a result, customary international law plays a significant role. The threshold test set out in Article 1(2) of AP II is still considered relevant,35 albeit with one important difference. Because the non-State actor is operating across a border and therefore partly in another State, or potentially in international waters, the situation is less likely to be considered as “internal disturbances and tensions”. This means that the threshold for this international form of niacs to all intents and purposes will be lower.
The law of armed conflict and the issues particularly relevant for the book will be examined in further detail in Chapter 5.
1.3.2 That Which Is Not Dealt With
1.3.2.1 Operations Not Involving Conduct of Hostilities or Self-Defence
In order to focus the book on issues relating to roe, loac and self-defence, operations below the threshold of armed conflict or before the commencement of an armed conflict are excluded. Furthermore, activities amounting neither to the ‘conduct of hostilities’36 nor involving personal self-defence are also excluded. This entails, inter alia, that law enforcement tasks and the roe and legal issues relating to such activities are not examined. In addition to being beyond the scope of the book, law enforcement has been declared not to be a nato function.37 It seems likely, however, that the challenges arising from hybrid warfare will cause this approach to change in order to enable nato forces to counter the use of unconventional weapons and tactics (‘asymmetric actions’), such as terrorism and other crimes, in hybrid campaigns on the territory of nato States prior to an armed attack.
In situations below the threshold of armed conflict, nato forces operating in areas where they may come into contact with forces from other States are likely to have roe controlling the use of force, should the need arise. This will also apply during an armed conflict in relation to States that are not party to the ongoing armed conflict. Whether force may be used to deal with such a situation, beyond the scope of personal self-defence, will be regulated by the jus ad bellum, in particular UN Security Council Resolutions and States’ right of self-defence.38 If the situation escalates beyond the threshold of armed conflict, loac will apply. The relationship between the jus ad bellum and loac or jus in bello is subject to debate. Because the approach taken to that discussion affects the question of legal basis for the use of force authorised by roe, it is examined separately and in detail, in Section 4.3.
1.3.2.2 Detention
While there may be some debate among nato States on whether detention amounts to the use of force, the decision was made to exclude detention from the book. The nato roe series on detention does not raise particularly challenging questions, but there is extensive legal debate concerning, inter alia, the legal basis for interning in niacs and the relationship between loac and ihrl with regard to the decision to detain, the legal review of that decision, and the duration of detention. This is not an area where loac and self-defence potentially interact and is therefore not dealt with in this book.
1.3.2.3 Other Areas of Law
Because the focus in this book is on the relationship between the two main ‘use of force’ authorities for military forces involved in an armed conflict, namely loac and self-defence, other areas of law are only examined to the extent relevant, as is the case of human rights law, or they are not covered at all. This does not mean that these are the only two relevant legal authorities; others may of course also be relevant for military operations,39 in particular for the nato roe authorising the use of force in other circumstances than the attack roe.40 Which areas of law will be applicable will depend on the context and the operation. While a detailed or exhaustive overview of other legal regimes is beyond the scope of this book, a few comments will be made to illustrate the legal complexities of military operations.
Depending on the operation, domestic law may affect the roe development. In operations in support of and on the territory of a nato State, the host nation will be able to influence the roe development and vote against (“break silence”41) any roe that authorise the use of force prohibited by their domestic legislation. Operations involving support of non-nato States may also include use of force authorised by domestic legislation, both in the form of force necessary to enable mission accomplishment and in instances where nato forces are supporting law enforcement authorities. Host nation law and authorities will be particularly important for operations below the threshold of an armed conflict. Compliance with the domestic laws of the respective Troop Contributing Nations (tcns) will usually not affect the roe development because it can be ensured through the use of caveats.42 It may, however, have an impact on roe application and interpretation, such as the ability to use lethal force to protect property or use military forces for counter-narcotics operations.
Other areas of international law of relevance to the development of nato roe for operations involving participation in an armed conflict will primarily be rules regulating activities not considered part of the armed conflict and hence unregulated by loac, but that are nonetheless part of the nato operation. For instance, if the operation involves maritime forces, unclos and customary international law of the sea will regulate inter alia the right to exercise sovereign rights of the coastal State, the right to visit and search and the right of hot pursuit.43 The degree to which force may be used is, however, limited by the duty to avoid adverse consequences such as creating hazards to the vessel or exposing the marine environment to an unreasonable risk.44 nato forces may also be tasked through a United Nations Security Council (unsc) resolution to conduct maritime interdiction operations, although the international rules regulating, for instance, prevention of terrorism or the proliferation of nuclear, chemical or biological weapons does not apply to activities of armed forces during an armed conflict, because loac will apply instead.45 Similarly, nato forces may be tasked with enforcing a no-fly zone, although the use of force involved during an armed conflict would be regulated by loac.46 One of the exceptional areas where the permission to use force has long been recognised is for the purpose of combating piracy,47 which may form part of a nato mission. Piracy may for instance prevent the desired establishment of a safe and secure environment in the area of operation, or pose a threat to nato or host nation forces.
nato operations may also include cyber operations. At the present, however, nato does not conduct cyberattacks, but conducts instead only defensive operations. The degree to which cyber measures will entail something akin to use of force, especially against persons which is the focus here, is therefore limited.48
1.4 Sources and Methodology
1.4.1 A Complex Picture
During military operations, more than one area of law is likely to apply at the same time. In order to give the best picture of the legal regulation of the use of force, it is therefore necessary to consider several areas of law. Because the decision has been made to focus on operations involving participation in an armed conflict, the main legal regime is loac. However, there is increasing recognition of the fact that ihrl also applies, at least to some extent. In addition, the use of force may be based on self-defence. The concept of self-defence is found in several legal regimes: the jus ad bellum, international criminal law (icl), and national criminal law. It has also been said to be a part of human rights law. The wide range of potentially applicable laws entailed that, in addition to identifying and setting out the applicable law, it has also been necessary to examine how the laws interact. In particular, there was a need to examine and clarify the understanding of the relationship between loac and ihrl,49 and the jus ad bellum and the jus in bello or loac.50
While there is extensive literature on the respective topics covered, there is only a limited amount considering how they relate, and even less examining the legal issues in the context of nato operations and roe. As a result, a wide variety of sources have been relied upon, including books, articles, manuals, doctrines, and conversations with experienced military personnel.
A general challenge faced in this research is the tendency for the same terms to be used with reference to different concepts. This relates both to States or practitioners, and to commentators. Because terms are commonly used without clarifying which concept is being referred to, it is necessary to first decipher which concept or interpretation is adhered to before examining the use or comments about them. The most pertinent examples in this context are the terms ‘hostile act’ and ‘hostile intent’, which for some are self-defence concepts but which for nato are defined as being threats or acts not giving rise to self-defence.51 As will be shown, this has been a cause of confusion, and these roe are commonly referred to as self-defence roe.52 A related issue is the fact that States differ in their interpretation of ‘use of force’. Attempts to define it in the nato context revealed that not all States consider ‘use of force’ to include both offensive and defensive force.53 Other examples are ‘necessity’ and ‘proportionality’, which are usually referenced in relation to roe without clarifying whether they refer to the loac principles, or law enforcement or human rights principles.54
There is also a tendency in international law to use terms without defining their meaning, and to accept that different States have different understandings of them. The term ‘combatant’, for instance, may be used both in a formal and functional sense. The former refers to State forces who have a right to participate in hostilities and who are entitled to pow status upon capture, while the functional use of the term refers to all those who are fighting.55 ‘Direct participation in hostilities’ is another area where there is extensive debate on what this concept entails and how it should be applied.56 The loac term ‘attack’ is also given different meanings. For AP I States, it includes the use of force in both offence and defence,57 while for instance the U.S. has emphasised that it only includes the use of force in offence.58 Defensive force is generally considered to be regulated by self-defence.59
‘Self-defence’ is a further example of a source of confusion. Unless it is specified, it may refer to State self-defence, unit self-defence or personal self-defence.60 Furthermore, as will be explained in Section 8.3, the term ‘self-defence’ also appears to be used to describe the operational authority to use force without roe, regardless of the legal basis. When it is stated in nato roe that it does not limit the inherent right of self-defence, what is the legal foundation for that right?
Many of these terms and the diverging views on their meaning go to the heart of the book, and the challenges they create are dealt with throughout the book as they arise.
1.4.2 International Law
According to Article 38 of the icj Statute, which is considered to reflect general international law, the primary sources of international law are treaties and customary international law.61 The definition of a treaty is found in the Vienna Convention on the Law of Treaties (vclt),62 Article 2(1)(a). A treaty is “an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation”.63 Customary international law is identified on the basis of State practice accompanied by an acceptance that the practice is required by international law (opinio juris sive necessitatis), or as phrased in Article 38(1)(b); “evidence of a general practice accepted as law”. Article 38(1)(c) also includes a third source of primary law, namely general principles of law recognised by civilized nations. Although rarely applied,64 the reference to personal self-defence as universal and inherent despite the lack of international treaty rules setting out such a general rule begs the question whether it is a general principle.
Finally, judicial decisions and writings of international experts may be used as secondary sources of how primary legal provisions should be interpreted.65 In addition to the sources recognised in Article 38, binding decisions of international organisations may also be a source of law for the States party to the convention establishing the international organisation,66 such as the United Nations.67 Resolutions and guidelines that are not developed as legally binding obligations, for instance because the international organisation responsible does not have the authority to create new international law, but are nonetheless intended to be respected, are sometimes referred to as ‘soft law’.68
There is some debate on whether there is a hierarchy of sources in international law.69 The approach taken here is that the sources should be considered in a successive order, with the result that treaty law and customary law are primary sources. Secondary sources should only be relied upon if and when primary sources are not sufficient, and may clarify rather than alter the application of the primary sources of law.70
The focus on armed conflicts and the use of force by military forces makes the law of armed conflict (loac, also known as international humanitarian law or the jus in bello71) a central source of law for this book. As will be further explained in Section 5.1.2, loac is perceived as an independent legal authority for the use of force, its application being triggered by the existence of an armed conflict. Through the concept of ‘combatant immunity’, loac permits acts that would otherwise be impermissible, such as the taking of life.
In the context of loac, both treaty law and customary international law play an important role. In addition to the Geneva Conventions of 1949 and their Additional Protocols, more historic sources of law, such as the 1907 Hague Convention V on Land Warfare (1907 Hague Regulations), still apply. There are also several treaties regulating the means of warfare.72 Because nato States have ratified different treaties, the most notable example being Additional Protocol I to the Geneva Conventions, there is no common nato approach to loac. As a result, where possible, customary international law is looked to in order to fill the gaps. Customary international law also plays an important role in the context of niacs, due to the limited body of treaty law. International experts have therefore sought to record the customary international law of armed conflicts. In particular, the 2005 icrc Customary Law Study is an important source of information on the rules that may be considered customary law.73 However, the study has been met with some criticism, and should therefore be applied as a secondary source of law rather than expression of customary law.74
In addition, expert manuals have been developed on some of the areas where the identification of existing law has been particularly challenging. Among the manuals relied upon in this book are the icrc Interpretive Guidance on the Notion of Direct Participation in Hostilities;75 the Air and Missile Warfare Manual;76 and the Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations.77 National loac manuals are also useful sources, and if a manual is formally endorsed as the State’s position on loac, it may be used as a source of State practice and opinio juris.
ihrl is regulated by fewer treaties. While all nato States have ratified the International Convention on Civil and Political Rights (iccpr),78 the United States and Canada are not parties to the European Convention on Human Rights (echr).79 The extent to which the differing treaty obligations affect the use of force during nato operations is examined in Section 4.2, including whether the right to life applies irrespective of treaty obligations, as customary ihrl. The treaty rules are complimented by judicial decisions, most notably by the European Court of Human Rights (ECtHR), and interpretive comments such as the General Comments developed by the Human Rights Committee (hrc).80 The ECtHR has in numerous cases considered the relationship between loac and human rights law and the potential for extraterritorial application of human rights law obligations, with varying and seemingly unpredictable results. Including human rights considerations in the book has therefore presented several challenges, resulting in a separate section on the question of lex specialis (Section 4.4). The approach taken is that loac is the lex specialis of armed conflict. Accordingly, although human rights law must be interpreted in light of loac during armed conflict, the lex specialis rule is not considered to displace the application of human rights completely.
Because the icl provisions relevant to the current book are not among the more controversial rules, this area provided few methodological challenges, despite the fact that not all nato States have ratified the Rome Statute. Similarly, because the focus with regard to the jus ad bellum is primarily on State self-defence, the main methodological challenge is the relationship between Article 51 of the UN Charter81 and the pre-existing customary rule. In addition, although the position taken here is that the use of force during an armed conflict is legally premised on the application of loac, others perceive the jus ad bellum as the legal basis for the use of force, even when loac applies.82 As a result, and as mentioned above, the relationship between the jus ad bellum and the jus in bello is examined in detail.83
States have taken different approaches to the relationship between international and national law. In some legal systems, international treaties apply domestically without legislation (monism). In others, international law must be given effect at the domestic level through a legislative act, for instance through the incorporation of the treaty into existing or new law (dualism). While States are generally considered to fall into one of the two categories, many legal systems combine elements from both approaches. The implications of this are, however, beyond the scope of this book.84
1.4.3 National Law
Because nato leaves it to the member States to define ‘self-defence’, their respective domestic self-defence rules are relevant to the examination of the ability of nato forces to use force during armed conflict. A study of domestic rules from different legal systems is not without its challenges. It is arguably impossible to fully understand a legal rule without having knowledge of the complete legal system it operates in and hence the context of the rule in question. For instance, while the wording of a rule may be comparable from one State to another, its application by the respective national courts may still be quite different. There are also practical challenges involved, such as the lack of language skills enabling national laws and legal decisions to be read. A comprehensive comparative study of the 29 nato States’ approaches to self-defence is not within the scope of this book. Nevertheless, where useful, an overview of relevant domestic law from select States has been provided in order to illustrate the different approaches taken and to demonstrate that the basic premises for self-defence relevant for this book are more uniform than perhaps expected.
The selection of examples is therefore based on two overall considerations. First, the availability of sources in a language I could work with, including commentaries on the interpretation and application of the self-defence rule to ensure the appropriate contextual understanding of the rule. Second, the decision was made to focus on States which are long-standing members of nato and whose perceptions of self-defence may have influenced the development of the MC 362/1.
1.4.4 nato Publications
The book relies heavily on nato publications, in particular the nato roe doctrine MC 362/1. This raised two challenges in particular. The first is whether nato publications fit into the lists of recognised sources of international law set out above. In particular, do nato roe have any binding force on nato States and troops participating in a nato operation respectively? This is dealt with extensively in Section 2.2.2. The important methodological conclusion is that roe are internal documents that are not intended to or perceived as creating legal obligations on nato States or legal justifications for the use of force. For individual members of the military forces, however, roe are legally binding as orders, and violations are regulated by national disciplinary and military penal law of the respective States.
The second challenge research on nato publications raises is that mission specific roe from current or recent operations are generally classified and therefore cannot be used in an open access publication. National interpretations on roe issues are, to the extent they are formalised, also often classified. The decision was therefore made to rely on the nato roe doctrine and to provide fictional examples of roe. The MC 362/1 is nato unclassified, which means that its contents may only be shared with the public for certain purposes. However, permission is given by the Military Committee to use aspects of it in this book.85
As a result of nato roe being classified, there are relatively few publications on the topic, and most of the discussions and lectures relevant for the research are classified. The solution has been to rely heavily on U.S. roe commentary, to the extent that it is relevant, and in the context of the nato hostile act and hostile intent roe in particular, to use non-classified discussions with experienced military personnel to enhance the arguments and examples in the book. Rigorous efforts have been made to ensure that the content of this book is non-classified.
The MC 362/1 is currently under review for update, and the proposals take some of the concerns raised here into account. However, because the draft has not yet been accepted by nato States and it is impossible to predict the final result, the current discussion has not taken the draft into account.
1.5 The Structure of the Book
The book is divided into four parts and 13 chapters. After this introductory chapter, Part 1 (Chapters 2 and 3) examines rules of engagement and the ‘use of force’ categories in nato roe. Part 2 identifies and sets out the relevant legal frameworks. First, Chapter 4 explains the approach taken to identifying the applicable legal basis for the use of force authorised by roe. This includes a consideration of the prohibition on arbitrary deprivation of life; the impact of the approach taken to the relationship between the jus ad bellum and the jus in bello, and an explanation of how the applicable legal regimes interact. The next chapters (5 and 6) go on to examine the law of armed conflict and self-defence respectively. Part 3 examines the scope of the ‘use of force’ categories in light of the applicable law. After a brief introduction in Chapter 7, Chapter 8 examines in detail the potential scope of applying self-defence during armed conflict, and distinguishes between the legal concept of self-defence found in criminal law and more operational forms of self-defence. Chapters 9–12 considers the roe ‘use of force’ categories in light of applicable law: from the use of force in response to attacks or imminent attacks by opposing forces; the use of force to accomplish designated tasks; the attack-roe permitting force to be used against persons demonstrating hostile intent or committing or contributing to hostile acts, and finally, persons ‘declared hostile’. Conclusions and recommendations are presented in Chapter 13, which makes up Part 4.
When referring to military personnel, terms such as military forces, soldiers, and troops will be used interchangeably and are intended to include all military servicemembers, whether soldiers, sailors, airmen or marines, as well as privates, non-commissioned and commissioned officers.
The reference to nato forces, operations or missions is intended to include both nato and nato-led forces, operations or missions. Furthermore, the reference to the use of force by nato forces should be interpreted as referring to the use of force by combatants, but not, for instance, medical personnel or civilian contractors, as this raises separate issues.
nato, Military Decision on MC 362/1 – NATO Rules of Engagement [hereinafter MC 362/1], 30 June 2003, p. 2, emphasis added. The MC 362/1 is nato unclassified, however, permission to use parts of the document for the purposes of this research is granted by the nato Military Commission in document imstam(O&P)-0006-2018 (copy on file with the author). See also nato, STANAG 2597: Training in Rules of Engagement, ATrainP-4 [hereinafter: STANAG 2597], 4 May 2015 (available at
As will be further explained in Chapter 5 (Section 5.1.1), loac is viewed as a legal basis for the use of force during armed conflict, distinct amongst others from the legal authority to use force under the jus ad bellum. See also Section 4.3, ‘The Relationship between the Jus ad Bellum and the Jus in Bello: Related in Fact, but Not in Law’.
See e.g. U.S., ‘Instructions for the Government of Armies of the United States in the Field’ (Lieber Code) [1863] Articles 23 and 44, printed in Dietrich Schindler and Jiri Toman, The Laws of Armed Conflicts (Martinus Nijhoff Publisher, 1988) pp. 3ff.
European Convention for the Protection of Human Rights and Fundamental Freedoms (echr) [1950], as amended by Protocols Nos. 11 and 14, ETS 5, Article 2(2) and 15(2); UN Human Rights Committee, Draft General Comment No. 36 – Article 6: Right to Life [hereinafter Draft General Comment 36], UN Doc CCPR/C/GC/R.36/Rev.2 [19 October–6 November 2015] para. 18; and Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, I.C.J. Reports [1996] 226, para. 25.
According to nato, hybrid threats “are those posed by adversaries, with the ability to simultaneously employ conventional and non-conventional means adaptively in pursuit of their objectives”. nato, ‘nato countering the hybrid threat’, act, 23 September 2011,
The reference to the term ‘fog’ in relation to war may be traced to by Carl von Clausewitz, who explained that “[w]ar is the realm of uncertainty; three quarters of the factors on which action in war is based are wrapped in a fog of greater or lesser uncertainty”. Carl von Clausewitz, On War (Michael Howard and Peter Paret (eds/trs), Princeton University Press, Princeton NJ, 1984) p. 101.
nato, MC 362/1 (n 3) p. 2. See also nato, STANAG 2597 (n 3) p. 1.
nato, STANAG 2597 (n 3) p. B-70.
ibid, p. B-73.
ibid, p. B-32.
ibid, p. B-33.
ibid, p. B-35.
ibid, p. B-37.
Classification of conflicts is examined in detail in numerous books and articles. For a thorough analysis, see Elizabeth Wilmshurst (ed.), International Law and the Classification of Conflicts (Oxford University Press, Oxford, 2012).
Article 2 common to Geneva Convention (I) for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field (GC I) [1949], Laws of Armed Conflict, printed in Schindler and Toman, The Laws of Armed Conflicts (n 6) pp. 459ff.; Geneva Convention (II) for the Amelioration of the Condition of the Wounded, Sick and Shipwrecked Members of Armed Forces at Sea (GC II) [1949], ibid, pp. 485ff.; Geneva Convention (iii) relative to the Treatment of Prisoners of War (GC III) [1949], ibid, pp. 507ff.; Geneva Convention (iv) Relative to the Protection of Civilian Persons in Time of War (GC IV) [1949], ibid, pp. 575ff.
Yoram Dinstein, The Conduct of Hostilities under the Law of International Armed Conflict (Cambridge University Press, Cambridge, 2016) p. 1.
icrc, Commentary on the First Geneva Convention – Convention (I) for the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field [hereinafter: GC I Commentary] (second edition, 2016,
Prosecutor v. Tadic (Decision on the Defence Motion for Interlocutory Appeal on Jurisdiction), Case No. IT-94-1-A, icty, Appeals Chamber [2 October 1995] para. 70.
GC I-IV Common Article 2 (n 18).
The specific rules of occupation are beyond the scope of this book.
icrc, GC I Commentary (n 20), commentary to Article 2, para. 218.
GC I-IV (n 18), Common Article 3, and if ratified and requirements for application are met; Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of Non-International Armed Conflicts (Protocol II) [1977], printed in Schindler and Toman, The Laws of Armed Conflicts (n 6) pp. 775ff.
Norwegian Armed Forces, Manual i krigens folkerett (Trans: Manual of the Law of Armed Conflict), issued under the authority of the Chief of the Defence [2013] [hereinafter: Norwegian LOAC Manual] p. 18.
William H. Boothby, The Law of Targeting (Oxford University Press, Oxford, 2012) p. 49. See also Prosecutor v. Tadic (Opinion and Judgement), Case No. IT-94-1-T, icty, Trial Chamber [7 May 1997] para. 562, where it is emphasised that a niac must be of certain intensity. For a detailed examination of the threshold for niac, see Yoram Dinstein, Non-International Armed Conflicts in International Law [hereinafter: niac] (Cambridge University Press, Cambridge, 2014) pp. 37–52.
See e.g. Norwegian LOAC Manual (n 26) p. 18. See also Dino Kritsiotis, ‘War and Armed Conflict: The Parameters of Enquiry’, Chapter 1 in Rain Liivoja and Tim McCormack (eds.), Routledge Handbook of the Law of Armed Conflict (Routledge, Milton Park, Abingdon, Oxon, 2016) p. 21, fn. 111. See also Francoise J. Hampson, ‘The relationship between humanitarian law and human rights law from the perspective of a human rights treaty body’, 90 International Review of the Red Cross 871 (September 2008) p. 555.
AP II (n 25), Article 1(2).
ibid, Article 1(1) states that the protocol will apply to “dissident armed forces or other organized armed groups which, under responsible command, exercise such control over a part of its territory as to enable them to carry out sustained and concerted military operations and to implement this Protocol”.
GC I-IV (n 18), Common Article 3 applies to “armed conflict not of an international character occurring in the territory of one of the High Contracting Parties”. On the distinction between AP II and Common Article 3 type niacs, see Boothby, The Law of Targeting (n 27) pp. 47–50; Dinstein, NIAC (n 27) pp. 38–50; and Marco Sassoli et al. How does law protect in war? Online,
See further Sections 4.2.1 (on the distinction between iac and niac in the context of human rights application) and 4.4 (on the relationship between loac and ihrl).
Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of victims of International Armed Conflicts (Protocol I) [1977], printed in Schindler and Toman, The Laws of Armed Conflicts (n 6) pp. 711ff, Article 1(4) refers to “armed conflicts in which peoples are fighting against colonial domination and alien occupation and against racist régimes in the exercise of their right of self-determination”. According to Boothby, the rule is of limited relevance today and may therefore be redundant. Boothby, The Law of Targeting (n 27) p. 47.
AP II (n 25) Article 1(1).
See e.g. icrc, GC I Commentary (n 20), commentary to Article 3, para. 386.
‘Conduct of hostilties’ refers to the use of means and methods of warfare by parties to an armed conflict. The ‘conduct of hostilities’ is regulated by loac.
nato, MC 362/1 (n 3) p. 6. It should, however, be noted that nato forces may in exceptional circumstances become involved in such tasks, if it is considered necessary for mission accomplishment and is authorised by a unsc resolution and the nac. Nikoleta-Paraskevi Chalanouli and Sherrod Lewis Bumgardner, ‘Rules of Engagement, nato’s Approach and National Caveats’, in Barbara Janusz-Pawletta (ed.), Zasady użycia siły (ang. Rules of Engagement) – wybrane problemy prawne [Rules of Engagement – legal problems] (Towarzystwo Wiedzy Obronnej, Warsaw, 2011) p. 107. Operations Ocean Shield and Active Endeavour are examples of such an exception. See Lone Kjelgaard, ‘The Importance of Law in the Theatre’, in Edoardo Greppi, Conduct of hostilities: the Practice, the Law and the Future, Proceedings of the 37th Round Table on Current Issues 2014 (International Institute of Humanitarian Law, 2015,
As explained in the UN Department of Peacekeeping Operations, Handbook on Multidimensional Peacekeeping Operations (United Nations, December 2003) p. 57, “sometimes the Security Council will authorize a peacekeeping operation to use armed force in situations other than in self-defence. The circumstances under which the operation may use armed force will then be spelt out in the relevant resolution of the Council”.
See also Kjelgaard, ‘The Importance of Law in the Theatre’ (n 37) p. 38.
This ‘use of force’ category is described in Section 3.4.
See further Section 2.4.2.
On caveats, see Section 2.4.2.
See United Nations Convention on the Law of the Sea, adopted at the Third United Nations Conference on the Law of the Sea (unclos), U.N. Doc. A/CONF.62/122 [1982] (reprinted in 21 I.L.M. 1261 [1982]) Articles 73, 110, and 111 respectively.
ibid, Article 225.
International Maritime Organization (imo), Protocol of 2005 to the Convention for the Suppression of Unlawful Acts against the Safety of Maritime Navigation [14 October 2005]
Program on Humanitarian Policy & Conflict Research at Harvard Univ. [hpcr], Manual on International Law Applicable to Air and Missile Warfare [hereinafter: AMW Manual] (2009, version 2.1 March 2010, hpcr, Harvard University) Section P, commentary para. 8, Rule 105(a-b) with commentary, and Rule 153(a) with commentary (aerial warfare). See also San Remo Manual on International Law Applicable to Armed Conflicts at Sea, Prepared by International Lawyers and Naval Experts convened by the International Institute of Humanitarian Law (Cambridge University Press, 1995) para. 97.
unclos (n 43) Articles 100 to 107 and 110. In order to deal with the piracy problems off the coast of Somalia, the UN Security Council has further expanded the unclos authorised in UN Security Council Resolution 1816 and subsequent resolutions, authorising states to use “all necessary means to repress acts of piracy and armed robbery”. UN S.C. Res. 1816 (Somalia), U.N. Doc. S/RES/1816 [2 June 2oo8], para. 7(b).
On cyber operations, see Michael N. Schmitt, Tallinn Manual 2.0 on the International Law Applicable to Cyber Operations [hereinafter Tallinn Manual 2.0] (2nd ed, Cambridge University Press, 2017).
See Section 4.2.
See Section 4.3.
See Section 3.5.
For instance, when members of the International Society of International Law and the Law of War, many of which are government legal advisers in nato states, were asked whether the legal basis for these roe is self-defence or mission accomplishment, the answers were divided: “the respondents are split in respect of the question whether roe’s authorizing ‘an attack on individuals and units carrying out a hostile act (not constituting an actual attack)’ or ‘demonstrating hostile intent (not constituting an imminent attack)’ constitute an expression of the right of self-defence or an expression of roes for mission accomplishment”. Terry Gill, Carl Marchand, Hans Boddens Hosang, and Paul Ducheine, ‘General Report’, in Stanislav Horvat and Marco Benatar (eds.), Legal Interoperability and Ensuring Observance of the Law Applicable in Multinational Deployments (Proceedings of the 19th International Congress, Quebec, xix Recueil of the International Society of Military Law and Law of War, Brussels, 2013) p. 151. See also Erica L. Gaston, ‘Reconceptualizing Individual or Unit Self-Defense as a Combatant Privilege’, 8(2) Harvard National Security Journal 283 (2017) p. 283, presenting the nato concepts as self-defence.
See Section 3.1.
The loac principles are introduced in Section 5.1.1, while proportionality is considered further in Section 5.5. On the self-defence principles of necessity and proportionality, see especially Sections 8.2.4 and 8.2.5.
See Section 5.2.2.
See Section 5.2.3.
AP I (n 33) Article 49(1).
See e.g. the criticism of the provision in U.S. Department of Defense (DoD), Conduct of the Persian Gulf War, Final Report to Congress, 31(3) ILM 1992, available at
See Section 5.1.3.
- 1.The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:
- a.international conventions, whether general or particular, establishing rules expressly recognized by the contesting states;
- b.international custom, as evidence of a general practice accepted as law;
- c.the general principles of law recognized by civilized nations;
- d.subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law.
- 2.This provision shall not prejudice the power of the Court to decide a case ex aequo et bono, if the parties agree thereto.
Statute of the International Court of Justice [18 April 1946] [hereinafter: icj Statute], available at
Vienna Convention on the Law of Treaties (vclt) [23 May 1969], U.N. Doc. A/CONF.39/27 [1969], reprinted in 8 I.L.M. 679 (1969).
ibid, Article 2(1)(a). According to Article 31(1), treaties must be interpreted “in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose”.
Antonio Cassese, International Law (2. ed., Oxford University Press, Oxford, 2005) p. 193.
icj Statute (n 61) Article 38(1)(d).
Cassese, International Law (n 64) pp. 185–187.
According to Article 25 of the UN Charter, “The Members of the United Nations agree to accept and carry out the decisions of the Security Council in accordance with the present Charter”. Charter of the United Nations (UN Charter) [24 October 1945] 1 UNTS xvi.
Cassese, International Law (n 64) pp. 196–197, and Anthony Aust, Modern treaty law and practice (Cambridge University Press, Cambridge, 2013) p. 49.
See e.g, Alain Pellet, ‘Article 38’, in Andreas Zimmermann et al. (eds.), The Statute of the International Court of Justice: A Commentary (Oxford University Press, Oxford, 2. Ed., 2012) pp. 841–848.
See also Cassese, International Law (n 64) p. 188. Others argue that there is no hierarchy among the sources. See e.g. Jan Arnold Hessbruegge, Human Rights and Personal Self-Defense in International Law (Oxford University Press, New York, 2017) p. 25.
These terms loac and jus in bello will be used interchangeably. In particular, jus in bello will be favoured when discussing its relation to the jus ad bellum.
See e.g. discussion in Section 8.2.6.
Jean-Marie Henckaerts and Louise Doswald-Beck, Customary International Humanitarian Law [hereinafter: ICRC CIL Study] (Cambridge University Press, Cambridge, 2005) available at
Boothby, The Law of Targeting (n 27) p. 40. See also the analysis in Elizabeth Wilmshurst and Susan Breau (eds.), Perspectives on the ICRC study on customary international humanitarian law (Cambridge University Press, Cambridge, 2007) and John B. Bellinger iii and William J. Haynes ii, ‘A US government response to the International Committee of the Red Cross study Customary International Humanitarian Law’, 89(866) International Review of the Red Cross 443 (June 2007).
icrc, Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law [hereinafter icrc Interpretive Guidance] (May 2009, prepared by Nils Melzer, available at
AMW Manual (n 46).
Tallinn Manual 2.0 (n 48).
International Covenant on Civil and Political Rights (iccpr) [16 December 1966] UNTS vol. 999, p. 171. Note that the U.S. does not recognise the extraterritorial application of the iccpr. See further Section 4.2.3.
echr (n 7).
See examples in Section 4.2.
(N 67).
See e.g. Geoffrey S. Corn et al., The Law of Armed Conflict – an Operational Approach (Wolters Kluwer Law & Business, New York, 2012) Chapter 1.
See Section 4.3.
For an explanation of the distinction, see Aust, Modern treaty law and practice (n 68) pp. 163–177.
See n 3.