The legal regulation of non-international armed conflicts has been of central importance in the post-Second World War evolution of international humanitarian law. Since one of the hallmarks of modern armed conflicts has been the participation of non-State armed groups, international judicial practice in the 1990s largely transposed the norms of international armed conflict to the field of non-international armed conflict. However, important differences remain between the two bodies of law, which necessitate the identification of the criteria separating international and non-international armed conflicts on the one hand, and non-international armed conflict and violent acts not reaching the threshold of an armed conflict on the other hand.

Substantive scholarship in the field of non-international armed conflict has been unfortunately sparse, with the sole comprehensive treatment being Lindsay Moir's wider book, The Law of Internal Armed Conflict (Cambridge University Press 2002). Anthony Cullen's book is therefore the first monographic attempt to undertake this immensely important task.

The book is divided into two parts. The first part, which accounts for more than half of the book, examines the development of the concept of non-international armed conflict, starting with the traditional categories of rebellion, insurgency and belligerency, and moving on to the entrenchment of non-international armed conflict as a separate normative category set forth in common article 3 to the 1949 Geneva Conventions and the changes brought about by the adoption of Additional Protocols I and II.

The second part of the book deals with the threshold in the application of the rules of non-international armed conflict. First, it focuses on the definition of non-international armed conflict put forward by the International Criminal Tribunal for the Former Yugoslavia in the Tadić Interlocutory Appeals DecisionFootnote ¹ and analyses the key aspects of the organization of parties and the intensity of hostilities. It then turns to the questions of territorial and temporal scope in the application of non-international armed conflict, the existence of armed conflict between non-State actors and responsible command. Finally, the monograph analyses the concept of non-international armed conflict in the Rome Statute of the International Criminal Court.

There is much to be liked about this book. It is written in a clear, concise language and the author perused a wealth of material. The first part of the book is characterized by a thorough analysis of the position of State delegates at the Geneva diplomatic conferences of 1949 and 1974–77 and this welcome reliance on the travaux préparatoires reveals the genuine intent of the drafters concerning the material scope of application of the Geneva Conventions and the Additional Protocols. An important conclusion drawn from the records of the negotiations is that the original scope of application of common article 3 was basically equivalent to the conditions of recognition of belligerency, ie full-scale civil war. The analysis of the threshold of application of non-international armed conflict is also based on a methodical survey of international jurisprudence—especially on the case-law of the ICTY—and the conclusions are logical and commendable from the point of view of providing expanded protection to the victims of armed conflicts. Possibly the finest section of the book is the meticulous dissection of article 8(2)(e) and 8(2)(f) of the Rome Statute, where by it convincingly argues for the application of a uniform concept of non-international armed conflict in the Rome Statute.

However, while there are strong features of the book, it does unfortunately miss out certain important aspects. First, the author does not explain his methodological approach hence it is not always completely clear whether his conclusions are drawn from customary international law or the results of a teleological interpretation of humanitarian law provisions. For instance, Cullen rejects the customary law status of wars of national liberation by relying on the famous statement of the International Court of Justice set out in the North Sea Continental Shelf Cases that required ‘extensive and virtually uniform’ State practice for the creation of custom (p 82). He also cited an impressive number of sources to prove the customary status of the Tadić definition (pp 120–122). However, the examination of the geographical scope of application of non-international armed conflict is solely based on ICTY jurisprudence and the findings about the temporal scope of application are gleaned from a single case of the Inter-American Commission of Human Rights (pp 140–146). Here the author seems to reach his conclusion on the basis of policy considerations as he emphasizes that the proposed solution ‘facilitates greater degree of clarity and cohesiveness’ and ‘the continuity of applicability is preserved by this position preventing interpretations of the law that would arbitrarily deprive victims of the protection it provides’ (p 142). To a certain extent, the overt reliance on international jurisprudence is inevitable, given the reticence of States to acknowledge the existence of non-international armed conflict and apply the respective legal framework. Yet, exclusive reliance on case-law means there is a risk of adopting legal standards which have been the result of judicial activism and do not reflect the actual intent of the primary law-makers, ie the States.Footnote ²

Another problematic aspect of the book is the narrow focus on non-international armed conflicts without any foreign element. Most contemporary conflicts involving non-State armed groups also contain transnational elements, for instance by foreign intervention to the conflict or the cross-border activity of non-State armed groups. According to a number of authors, the law of non-international armed conflict is the applicable framework to such ‘transnational armed conflicts’.Footnote ³ Given that the study sought to ‘present an approach to the interpretation of important distinctions which define the concept of the non-international armed conflict in international humanitarian law’ (p 3) it is difficult to comprehend the complete absence of any reference to this topic.

The lack of utilization of any foreign language writings is also regrettable. While arguably the main conclusions need not have been substantially modified had the author consulted any non-English literature, it might have provided additional arguments. This is amply illustrated by the fact that Cullen devotes considerable space to discussing the potential significance of the changing of the phrase ‘protracted armed violence’ used in Tadić definition to ‘protracted armed conflict’ in article 8(2)(f) of the Rome Statute (pp 174–179) but fails to notice that this difference might be due to a simple mistranslation from French to English of the original proposal of Sierra Leonean delegation.Footnote ⁴

Nevertheless, all these criticisms have to be balanced against the achievements of this pioneering book. Despite its shortcomings, Cullen has produced an important piece of scholarship which will be used in education and practice for years to come.