About the author(s):
Dr Nathan Derejko is a Lecturer in the School of Law and Human Rights Centre at the University of Essex. Previously, Nathan was Director of the Human Rights Centre Clinic at the University of Essex, Director of the Masters in Human Rights Programme at University College London, and a visiting lecturer at the International Institute of International Humanitarian Law in Sanremo, Italy.
Nathan’s research and teaching interests span three interrelated fields: International humanitarian law, international human rights law, and the use of force under the jus ad bellum. He has a particular interest in the applicability and application of human rights during armed conflict, counter-terrorism and human rights, and the law and practice of non-international armed conflicts. Nathan is also actively engaged outside of academia, and has previously worked with a number of human rights and humanitarian organisations in Canada, Europe, East Africa and the Middle East, and continues to deliver advanced training sessions for military personnel and government agencies, support strategic litigation efforts, and serves as an expert member for various NGO committees. Nathan is currently on the Defend Digital Me Advisory Council, an NGO focused on children’s rights to privacy and family life. Nathan Tweets at @NathanDerejko
Having spent the better part of a decade researching, writing, thinking, and teaching non-international armed conflict (NIAC), I am delighted to share the culmination of that work: my recent Cambridge University Press monograph, Identifying Non-International Armed Conflict: International Law and Practice. To mark the publication, Articles of War and Armed Groups and International Law are co-hosting a book symposium featuring an outstanding lineup of international humanitarian law (IHL) experts who will engage with key themes and arguments from each chapter.
I want to express my sincere thanks to the editorial teams at both Articles of War and Armed Groups and International Law for organising and facilitating this symposium, and to the distinguished IHL academics and practitioners who generously devoted their time to reviewing and responding to the book, including Gloria Gaggioli, Chiara Redaelli, Jelena Pejic, Katharine Fortin, René Provost, and Martha Bradley. It is a genuine honor to have you all engage with the book, and I am very much looking forward to the discussions.
This introductory post serves a modest purpose: to offer insight into the historical evolution of the book, outline the core motivations driving the research along the way, and summarize its overarching objectives and structure.
The book began its life as research into the use of force and the right to life in the so-called Global War on Terror (GWOT). It quickly became clear that the foundational legal question was whether the GWOT constituted an armed conflict under IHL. Addressing this foundational question required untangling the complex web of international armed conflicts (IAC), NIACs, mixed armed conflicts, and various (counter-terrorism) military operations outside of armed conflict, all of which were all too often simply conflated under the banner of the “war on terror.”
Once the research focused specifically on NIACs, a range of unresolved legal questions emerged. It quickly became clear that few of these issues enjoyed consensus in the academic literature, and even fewer were governed by clear, explicit rules under positive IHL. These inquiries spanned both normative and doctrinal issues: Are the concepts of civil war, internal armed conflict, and NIAC legally coterminous? How and why did the plurality of NIAC develop within IHL, and what is the relationship between Common Article 3 (CA 3) and Additional Protocol II (AP II) in practice? What precise factual and legal conditions are necessary to activate a NIAC, and through what mechanism(s) is this determination made? Can a NIAC exist across multiple territories simultaneously, and if so, what is the precise geographical scope of IHL in adjacent or remote territory? Does IHL shadow individuals as they move away from battlefields of NIAC, and is this determination based in individual status or conduct? What is the legal status of members of organized armed groups, or put differently, who qualifies as a civilian during NIAC? Finally, by what factual and legal standard(s) does a NIAC end?
These core questions regarding the material, personal, geographical, and temporal parameters of NIAC eventually formed the structural foundation of the book across six chapters. The exception to this research and thought progression was Chapter 3, which addresses the classification of battlefield actors. Looking back, this chapter emerged from my attempt to comprehensively identify and map the vast number of armed groups operating in Syria and the various parties to which they belonged. This task, while ultimately unsuccessful, revealed the pressing need for a coherent analytical framework for determining which armed groups are fighting on behalf of which parties. Ultimately, Chapter 3 became central to the book’s cohesive framework: it offers a framework for delineating the external parameters of a party to a NIAC, determining the number and types of NIACs occurring within a specific geographical and temporal frame, and determining if and when new arrivals on the battlefields of existing NIACs were bound by and subject to IHL.
Developments Driving the Research
Several overarching motivations informed the research underpinning this book, many of which emerged directly from State and non-State practice in NIACs prevailing over the course of the research. Four key issues, however, were particularly influential in shaping the scope and direction of this book and warrant brief elaboration.
First, the far-reaching legal consequences of the existence of a NIAC and the applicability of IHL. The existence of a NIAC triggers the applicability of IHL, which, although it does not displace international human rights law (IHRL) altogether, nonetheless modifies the content and scope of its protections by recalibrating the legal parameters regulating the use of lethal force and detention of individuals for reasons related to the NIAC.
The existence of a NIAC also holds jurisdictional significance under international criminal law (ICL), as in the absence of an armed conflict there can be no war crime. The existence of NIAC may also customize the concept of terrorism, as the applicability of IHL recalibrates the content and scope of “terrorist offences” under international counter-terrorism law. As the concept of NIAC is not geographically restricted to the territory of a single State, so-called “transnational NIACs” or extra-territorial NIACs may invariably implicate the jus ad bellum.
A range of domestic legal implications may also come into effect with the existence of a NIAC and the applicability of IHL, whether in terms of activating a legal authority to deploy the armed forces under the rubric of IHL, assessing asylum or subsidiary protection claims, or the activation of war exclusion clauses in insurance contracts. Evidently, whether a situation is one of armed violence or NIAC is of pivotal importance across multiple bodies of international and national law.
Second, the applicability of IHL often carries profound consequences for civilians and the civilian population. Traditionally, the law of NIAC was predominately viewed as prohibitive and protective; shielding civilians from the effects of armed conflict, safeguarding the wounded and sick and individuals hors de combat, and ensuring humanitarian access to civilians in need. Hence the view that CA 3 should be applied as “wide as possible” as there can be “no drawbacks in this.”
However, this traditional view predates the emergence and progressive development of IHRL, and whether it remains true today is open to debate. Indeed, a growing consensus recognizes that CA 3 not only prohibits, but also permits conduct otherwise prohibited by IHRL. While targeting and detention are often used as illustrative in this regard, it is important not to lose sight of civilian harm that is the result of otherwise lawful military operations. By way of the principle of proportionality in attack, IHL permits, or at least tolerates, civilian harm as long as it is not excessive in relation to the concrete and direct military advantage anticipated. This dynamic is further exacerbated by narrow interpretations of civilian harm that routinely exclude indirect, reverberating, or cumulative effects.
More recently, interpretations of IHL are increasingly divorced from their object and purpose, at times skewing the balance between military necessity and humanity, and in the absence of clear violations, invoked to justify a scale of death, injury and destruction that IHL was arguably developed to avoid. While the question of whether CA 3 is the proverbial shield or sword is open to debate, within the current framework of international law it is clear that the activation of CA 3 no longer fills the legal void in protection as it did in 1949, but arguably may invariably reduce the existing protections afforded by IHRL.
Third, the factual and legal distinction between situations of armed violence and NIAC has become increasingly blurred, producing fertile ground for a new era of overclassification of situations of armed violence. While the so-called “global war on terror” is perhaps the epitome of this conflation, it is not the only example. The prevailing debates as to whether the military operations of the G5 Sahel Joint Force in West Africa should be conducted in accordance with the rules of IHLR or IHL, or some combination of both, is another example. Along similar lines, whether the recently established Gang Suppression Force in Haiti is required to operate under IHRL or IHL is also debated. The gravity and scale of armed violence between criminal organisations in Rio de Janeiro, and the enduring violence between competing drug cartels in Mexico have sparked debates on whether “organized criminal violence” can amount to a NIAC under IHL.
These are not merely academic debates. In 2024, the President of Ecuador, Daniel Noboa, issued a decree declaring an “internal armed conflict” against 22 criminal groups operating in Ecuador labeled “terrorists” and ordered the armed forces to carry out “military operations, under international humanitarian law and respecting human rights to neutralize” these groups. Since September 2025, the United States has continued to conduct lethal strikes against alleged drug trafficking boats in the Caribbean and Eastern Pacific under the legal pretext that the United States is engaged in a “non?International armed conflict” with unspecified drug cartels, and that the United States is conducting its military operations against the cartels “pursuant to the law of armed conflict.” In contrast to historical practice, States are increasingly asserting the existence of a NIAC in situations where the prevailing factual circumstances suggest otherwise, seemingly incentivized to invoke IHL not as a constraint on their authority or conduct, but as a permissive framework that relaxes the more stringent law enforcement standards imposed by IHRL.
Fourth, the absence of a legal mechanism or central authority within international law to pronounce on the existence of a NIAC and the applicability of IHL. In practice, conflict identification occurs on an ad hoc basis across domestic, international, judicial, and non-judicial entities in accordance with their respective mandates. The various motives that drive each of these actors to identify NIAC invariably influence their respective determinations. Indeed, it is not uncommon for multiple actors to reach different conclusions as to the existence of a NIAC based on the same factual circumstances.
For example, the UN Human Rights Council’s Commission of Inquiry (COI) (pp. 32-37), the International Crimina Court (ICC) (p. 7), and the International Committee of the Red Cross (ICRC) (2013, p. 124; 2014, p. 123) all arrived at different conclusions with respect to the beginning of the NIAC in the Central African Republic. The COI went so far as to change its initial assessment from its preliminary report to the Security Council, holding that it,
considers that it is best to err on the side of caution and to avoid blunt classifications that may provide a greater degree of legal certainty and facilitate the continuing and uninterrupted application of international humanitarian law but that do not accurately reflect the nature of the events on the ground (p. 37).
However, these conflicting interpretations are not only the result of the motives that drive them, but also the result of a broad spectrum of uncertainties surrounding the legal concept and contours of NIAC.
The Objectives and Structure of the Book
The focus of the book is on the identification of NIAC under international law. The book is divided into six chapters, each of which explores a composite element of NIAC.
Chapter 1 examines the material scope of NIAC contained within CA 3 and AP II, including how the drafters understood these concepts and how they have been interpreted and applied in practice. It continues by highlighting some of the practical and operational challenges that emerge from the plurality of NIAC under IHL. These challenges, coupled with developments within conventional and customary IHL applicable during all NIACs, compel consideration of the continued relevance of the plurality of NIAC under IHL. The chapter undertakes a comparative analysis of the material scope of NIAC, both as formulated in the Tadi? definition and as contained in AP II, is undertaken to identify areas of convergence and divergence, and to assess the continued relevance of the distinction between CA 3 and AP II NIACs in practice. One of the main conclusions of the chapter is that the Tadi? definition and corresponding Tadi? Test for NIAC has essentially harmonized the thresholds of activation of CA 3 and AP II, and largely, albeit not entirely, harmonized the applicable IHL to both variants of NIAC.
As a NIAC is a limited manifestation of a broader concept of armed violence, Chapter 2 focusses on the threshold of NIAC. In practical terms, determining the threshold of NIAC is an exercise in the qualification of armed violence. This chapter begins by examining certain manifestations of armed violence that are prima facie excluded from the ambit of NIAC. It continues by advancing a three-step analytical process for determining this threshold: 1) identifying the material elements of NIAC; 2) evaluating the intensity of the armed violence; and 3) assessing the organizational capacity of the entities engaged in the armed violence.
This chapter concludes by examining the various actors that pronounce on the existence of a NIAC, and the legal consequences of such pronouncements. One of the central arguments of the chapter is that the threshold of NIAC is linked to the exhaustion of the law enforcement regime’s ability to prevent or suppress prevailing armed violence, thereby establishing a high threshold for the existence of a NIAC and the activation of IHL.
Once a NIAC exists, the parties to a NIAC rarely remain static or singular. The proliferation of battlefield actors during NIAC renders it increasingly difficult to determine the number of NIACs occurring within a specific geographical area, to attribute battlefield conduct to a party to the NIAC, and to determine if and when new actors on the battlefield are bound by and subject to IHL.
Chapter 3 addresses these challenges by proposing a normative framework for the classification of battlefield actors during NIAC. First, it examines the concept of a “party” to a NIAC, and the distinction between a party and the armed forces of a party to a NIAC. Second, in order to define the external parameters of a party to a NIAC, it explores the concept of “belonging” to a party to an armed conflict under IHL. Third, to determine if, or when, new battlefield actors are bound by and subject to IHL during NIAC, it explores the concept of “supporting” a party to a NIAC. This chapter creates a normative and doctrinal framework to evaluate whether a constellation of seemingly independent armed groups operating within a single geographical and temporal frame may constitute a single party to a NIAC.
Once a NIAC exists, IHL imposes a broad range of obligations and protections upon entities and individuals participating in or otherwise affected by a NIAC. It is thus necessary to identify the principal bearers of IHL obligations during NIAC, as well as the primary beneficiaries of IHL’s protections. This personal scope of IHL during NIAC is the focus of Chapter 4.
The chapter begins by comparing the conventional architecture of CA 3 and AP II to determine whether it is possible to speak of a singular personal scope of IHL during NIAC. It then identifies the primary entities and individuals that have obligations under IHL, as well as the range of entities and individuals entitled to IHL protections. This chapter concludes by considering the relationship between obligations and protections by examining the phenomenon of intra-party violence during NIAC. One of the key takeaways from this discussion is that IHL should be viewed as applicable between non-opposing forces during NIAC and regulating intra-party armed violence to ensure humane treatment.
The advent of drones and the emergence of the so-called “global battlefield” have challenged traditional assumptions of the geographical scope of IHL during NIAC. This is the focus of Chapter 5.
It begins by examining the two leading approaches for determining this scope: the “territorial approach” and the “battlefield approach.” Based on the conclusions of these two sections, it advances and explores an alternative “functional approach.” Chapter 5 concludes with an examination of the legal architecture that regulates the pursuit of extraterritorial hostilities during NIAC, including the consent of the territorial State, Chapter VII authorization from the UN Security Council, and the exercise of self-defence under the jus ad bellum. One of the key takeaways of Chapter 5 is that examining how and when IHL operationalizes during NIAC, will determine its geographical reach. Moreover, while the jus ad bellum may function to restrict NIACs territorially, it does not restrict the geographical scope of the jus in bello.
The looming threat of the so-called “forever war” has revealed that determining the end of a NIAC is just as complex as determining its existence. Chapter 6 explores the temporal scope of IHL during NIAC with an exclusive focus on IHL’s threshold of termination.
It begins by examining the two leading approaches for determining the IHL’s threshold of termination: the “peaceful settlement” approach developed within ICL and the ICRC’s “lasting pacification” approach. Based on the conclusions reached, it once again advances and explores an alternative “functional approach” for determining the end of IHL’s applicability. One of the key takeaways from this discussion is that because the law of NIAC consists of a broad range of obligations that regulate different factual contexts, their temporal scope of applicability inescapably varies. As a result, any approach to identify a single point in time to terminate the applicability of IHL in toto is not fit for purpose.
The International Law of Conflict Identification
The book approaches the identification of NIACs from the perspective of IHL. As with all law, however, IHL evolves and is subject to interpretation, but this interpretation cannot be carried out in isolation from other legal regimes equally applicable during NIAC. Moreover, many issues surrounding the identification of NIACs do not benefit from the conventional guidance of black letter law in IHL or conclusive State practice. Indeed, what has proven to be the most authoritative definition of NIAC, including its geographical and temporal boundaries, has emerged from the International Criminal Tribunal for the former Yugoslavia (ICTY)’s Tadi? case.
As a result of the silence of IHL on a number of issues addressed in the book, the book draws normative and doctrinal guidance from other legal regimes equally applicable during NIAC, including ICL, IHRL, and to a lesser extent, national law. It has recourse to these legal regimes to interpret the provisions of IHL that have a direct bearing on the concept of NIAC itself, including its threshold of activation and corresponding personal, geographical, and temporal scope of IHL’s applicability. In areas where these legal regimes fall short of providing sufficient guidance, the book draws insight from the law of international armed conflict under IHL. While this study draws from the judicial contributions of other legal regimes, it will nonetheless highlight areas where their respective interpretations arguably diverge from the normative and doctrinal foundations of IHL. The forward strategies proposed over the course of the book attempt to balance the (potentially) competing legal regimes, while remaining faithful to the object and purpose of IHL during NIAC. For the purposes of the book, the object and purpose of IHL during NIAC is to regulate the conduct and consequences of hostilities.
Concluding Thoughts
The factual and legal criteria for establishing the threshold of NIAC, along with its personal, geographical, and temporal scope, remain complex and contested. Identifying Non-International Armed Conflict: International Law and Practice,critically examines several of these outstanding legal issues, evaluating current law and practice while proposing alternative approaches grounded in the object and purpose of IHL. The following symposium convenes leading IHL experts to discuss the book’s central themes and arguments, aiming to foster greater clarity and consensus on the legal concept and contours of NIAC. I am very much looking forward to forthcoming discussions and will provide some reflective thoughts in a concluding post.