In the seventeenth century, the Treaties of Westphalia equated sovereignty with supreme control and absolute authority, giving rise to the principle of non-intervention. However, this traditional legal view has been challenged by humanitarian crises, particularly during and after World War II. The early years of the twenty-first century saw the emergence of the concept of the ‘responsibility to protect’ (R2P) as a means for safeguarding human beings.Footnote ¹ However, this concept has been controversial since its inception. Some scholars have expressed their doubts concerning the R2P, finding it to be an empty shell, which cannot be made ‘principled’; is difficult to ‘standardise’ and even harder to ‘regularise’; and simply cannot be made to work in practice.Footnote ²

Stacey Henderson responds to this critique in Atrocity Crimes and International Law. She argues that the R2P is more than just empty rhetoric, rather that it is motivating, changing and shaping State behaviour (157). Throughout her analysis, Henderson finds a balance between protection of sovereignty and protection of populations—re-conceptualising the idea of intercession. She believes that intercession can serve to capture and explain changes in State practice as well as to illustrate the impact of R2P on the development of international law.

This book is divided into seven chapters. Chapters 1 and 2 focus on the introduction of concepts and views concerning the R2P. Chapter 1 briefly outlines the evolution of the concept, from its original formulation to its eventual adoption at the 2005 World Summit and the subsequent Secretary-General reports on its implementation, which provides context for the detailed analysis of State practice that is conducted in the chapters that follow.

Henderson stresses that the R2P is a powerful concept of Statecraft which has provided a conceptual solution to the failings inherent in Westphalian sovereignty—sovereignty as responsibility.Footnote ³ At the same time, the R2P is of legal significance in that it has permitted and inspired an evolution in State practice (17). Chapter 2 introduces and develops an original conceptual tool inspired by R2P, intercession. This chapter provides an overview of the different non-forceful measures that fall within intercession and highlights the significant changes in recent State practice as States increasingly begin to use measures less than the use of armed force to respond to atrocity crimes occurring in other States.

Chapters 3 to 6, through a close analysis of State practice and treaty texts, examine how non-forceful measures under the R2P were applied and implemented in the responses of the international community to impending or actual atrocity crimes, such means including: diplomatic measures; economic sanctions; arms restrictions (the formulation and imposition of an Arms Trade Treaty); and assistance to opposition groups. According to Henderson, the choice is never one of action or inaction, but rather involves choosing between the many tools available, consistent with the national interest in garnering the political will required to help protect populations from atrocity crimes (158). By the careful study of national examples, she describes the ‘accordion effect’ of intercession: an increasing range of situations where States can lawfully take measures of intervention, tempered by restrictions on the measures imposed and the manner in which they are implemented (27).

Chapter 7, the final chapter, draws the previous analysis together and concludes that the R2P is something more than empty rhetoric and is shaping the evolution of State practice in diverse areas (164). It is also argued that the R2P is being mainstreamed and integrated into the text of the Arms Trade Treaty, helping to construct the contours of various forms of dialogue such as power negotiation and interest weighing.Footnote ⁴ Inspired by the ideals of the R2P, measures of intercession have provided a solution to the dilemma of articulating when and how the international community might respond to atrocity crimes occurring in other States.

Henderson argues that the R2P has brought about an evolution of the principles of State sovereignty and non-intervention, and inspired the emergence of a practice whereby States choose non-forceful responses to atrocity crimes committed in other States, to better protect vulnerable groups. She proposes a new conceptual framework (intercession) to examine this evolution in State practice. The contribution of the R2P is no longer merely conceptual. It is helping shape the boundaries of traditional international principles of sovereignty and non-intervention, and the evolution of State practice.

In summary, Atrocity Crimes and International Law is an excellent work which is of relevance to international law, international relations, humanitarian law, and peace and security studies, offering a logical and clear argument, and supported by appropriate and persuasive case studies. The book offers insights into the emerging behaviours of States in a vital area. Henderson examines State practice in response to atrocity crimes through the prism of intercession, revealing the power of ideas to prompt change in international law and inform the advancement of the R2P framework in a meaningful way, while also powerfully countering those who continue to challenge the existence of the concept.