The modern world is characterised by dynamism, with the speed of change increasing rapidly. This dynamism poses challenges for governance and specifically for law, which aims to provide stability but must also adapt to societal changes. However, there is little understanding of the actual changes in international law—the extent of its dynamism—and the various elements that contribute to or hinder this dynamism. To illuminate this underexplored subject, Nico Krisch and Ezgi Yildiz have gathered an impressive range of international lawyers and political scientists to take readers on an intellectually stimulating journey through the complex and evolving landscape of international law in the edited volume The Many Paths of Change in International Law. With empirical breadth, conceptual creativity and interdisciplinary rigour, they perceive international law as a dynamic field, confronted by the tension between stability and inertia on the one hand, and the driving forces of change on the other, whether the changes are significant or even seemingly modest yet meaningful.

In terms of structure, the volume revolves around four themes, each delving into distinct dynamics inherent in various paths of change within international law. Specifically, there is an examination of the strategies, forms and forces driving change, followed by a reflection on how these change processes and their diverse implications can be contextualised within the realms of international law and politics. This volume offers the first comprehensive theoretical framework and analysis of how international law undergoes changes via mechanisms including, but not limited to, traditional treaty-making.

Part II is dedicated to strategies of change. According to Mark Pollack’s analysis of Donald Trump’s first administration and its lasting impact in Chapter 2, strategy plays a crucial role in change processes. Different strategies are tailored to specific change attempts, with traditional change agents influencing international legal norms through ‘negotiation, interpretation, and adjudication’ (65), while hostile change agents employ more aggressive means to circumvent and undermine international rules. By examining the policies of the first Trump administration in relation to international trade, Pollack concludes that it acted as a hostile change agent, aiming to weaken the international rule of law. Pollack also suggests that it is crucial for defenders of international law to consider strategies and tactics to mitigate negative impacts. In Chapter 3, Pedro Martínez Esponda discusses actors’ strategies regarding the right to self-defence against non-State actors. Various strategies of destabilisation, such as ‘multilateral ambiguity, selective protest, compromised support, and cryptic precedent’ (88) contribute to the unstable status of this norm. Nina Reiners, in Chapter 4, examines the role of experts and their collaboration with international expert institutions in shaping international law through interpretation. Reiners refers to this symbiotic relationship as ‘transnational lawmaking coalitions’ (94) and explains how they come together and employ strategies to generate change. The combination of these diverse strategies employed by different actors unveils the dynamics involved in shaping international law and driving change processes.

The form of change is important for creating opportunities for successful implementation, as Part III highlights. As noted in the Introduction, ‘interpretive change construed incrementally over time’ (27) often leads to less contention and higher chances of success. In Chapter 5, Tonya Putnam examines how the understanding of the obligation to prevent genocide in the Convention on the Prevention and Punishment of the Crime of Genocide evolved incrementally over time without formal amendments. This shift emphasised positive obligations to protect vulnerable populations in States with incapable governments. Chapter 6, authored by Wouter Werner, delves into the dynamics of restating and codifying existing laws, focusing on the International Law Commission’s (ILC) Draft Conclusions on the Identification of Customary International Law. Werner argues that this mode of change involves a dialectic process. Despite their political nature, restatements are not seen as new creations but as recursive exercises that build on existing materials. Jaye Ellis explores the world of metrics in Chapter 7, highlighting how metrics-based governance diverges from traditional modalities of change in international law. As shown by Ellis, the adoption of performance-oriented metrics, exemplified by the United Nations Sustainable Development Goals and the Paris Agreement, were a response to the limitations of multilateral rulemaking. This shift moves change processes beyond legal norms and into ‘the space for bureaucratic, technocratic, and expert-driven solutions’ (174). However, Ellis argues that, in a speculative context, metrics and legal norms can coexist and interplay.

Part IV focuses on the broader forces that drive change, such as shifts in power, ideas or actor configurations. Chapter 8 examines the impact of new challenges to human rights law. Wayne Sandholtz emphasises that international legal change can also be non-liberal, and analyses how authoritarian regimes undermine international human rights institutions. Sandholtz highlights that as the number and strength of authoritarian regimes increase, their adverse impact on human rights norms and institutions grows. However, there are also factors that provide resilience against these challenges, including what Sandholtz has described elsewhere as ‘the resilience of rights’ (195). Chapter 9 explores the broader effects of the rise of human rights and environmentalism. Seline Trevisanut investigates how other fields of international law have driven change in the law of the sea, including ‘multilateral, bureaucratic, and private authority’ (226) pathways that have channelled change from human rights and environmental law. In Chapter 10, Nina Kiderlin focuses on the effects of major power shifts in the context of the World Trade Organization (WTO) rules on subsidies. Realising that the negotiation-driven multilateral path was unlikely to bring significant change, China shifted its efforts to the WTO dispute settlement system, which Kiderlin notes was a strategy that required long-term investment in legal expertise.

Part V examines change processes from a broader perspective, considering their doctrinal reconstruction, sociological framework and political context. Chapter 11 focuses on the institutions involved in international legal change. Jeff Kucik and Sergio Puig analyse how the WTO Appellate Body (AB) operates and brings about change, particularly in response to political challenges. Through a quantitative analysis of the AB record, they find that the AB is more likely to adjust its jurisprudence when previous decisions resulted in non-compliance by States. In Chapter 12, Dorothea Endres explores the sociological frames through which change in international law is constructed. She notes the difficulties in assessing incremental change when different communities of practice have diverging conclusions on whether change has occurred and who has the authority to identify it. In the absence of a central authority, various positions may persist, making consolidation challenging. Fuad Zarbiyev’s Chapter 13 offers a process-oriented analysis of changing interpretive authority in international law. He traces how the ILC challenged States’ ultimate authority in treaty interpretation through its Draft Conclusions on Subsequent Practice. This marks a shift from the traditional reliance on State authority towards a ‘legal regime of treaty interpretation’ (297) and alternative interpretative authorities. In Chapter 14, Ingo Venzke delves further into the relationship between legal change and its surrounding context. He argues against reducing law solely to its context, emphasising the importance of internal reasons for change and contending that historiography only makes sense on the presumption of such internal contingency. He thus proposes exploring alternative pathways of change independent of external circumstances, shedding light on this contingency. In the epilogue, BS Chimni reflects on the insights gained from the volume and the limitations of its framework. He highlights the significance of incremental change, which has become dominant due to the saturation of treaties. Chimni calls for a better understanding of the politics behind incremental change to harness its potential for counter-hegemonic movements.

Understanding the changes in international law is like exploring uncharted territories with courage and accuracy. It involves breaking away from established ideas and paying attention to details. This may seem an impossible task, but the book manages to achieve this. By integrating perspectives from international law, international relations, sociology and legal theory, it stands as an unparalleled companion, illuminating and deciphering the multitude of approaches that encompass the realm of international law. The theoretical framework it presents facilitates analysis of the dynamic nature of the international legal order, which aids in understanding the processes of change and their diverse implications within both international law and politics. This thought-provoking book is highly relevant for anyone seeking to comprehend the intricacies of change and its consequences in the field of international law.