In Voluntary Disruptions, Abraham L. Newman and Elliot Posner employ an historical institutionalist approach to strongly advance our understanding of both international soft law and the politics of financial regulation. The authors define soft law as “a set of written advisory prescriptions” that can include voluntary codes of conduct, technical standards, best practices, and written guidelines (p. 2). However, where most previous studies have focused on the creation of and compliance with international soft law, Newman and Posner seek to examine its second-order effects in producing disruptive and distributional consequences over time. They do so, empirically, through detailed studies of the post-Bretton Woods international financial architecture, the rise of industry groups such as the Institute of International Finance, and the politics of financial regulation in the European Union before the 2008 crisis and in the United States after it.

Overall, Voluntary Disruptions is a theoretically informed and empirically rich book that makes a number of valuable contributions. First and foremost is its use of historical institutionalism, which highlights the importance of second-order effects and views domestic and international politics as mutually constituted; the authors explicitly note, “This book belongs to the recent trend in IR scholarship that borrows from the historical institutionalist toolkit” (p. 169). The result is that Voluntary Disruptions treats international soft law as an institution that evolves over time, produces distributional consequences, and carries its own path dependencies and feedback effects. Moreover, it is these path dependencies and feedback effects that underpin the two key mechanisms through which international soft law creates second-order effects: legitimacy claims and arena expansion.

For Newman and Posner, legitimacy claims occur when domestic political actors use the existence of international soft law to legitimize their own policy preferences and thus bolster their positions in domestic political competition. Specifically, to the extent that domestic actors can frame international soft law as state of the art and politically neutral, it can serve as a type of third-party validation that tips the balance in close political contests. They write, “Soft law unsettles the contest by providing new political resources to some regulatory factions as they advocate for and advance their positions or attack and erode the positions of others” (p. 25). As a result, the presence or absence of international soft law in specific policy areas can help explain variation in empirical outcomes.

In addition to legitimacy claims, international soft law can also create second-order effects through the mechanism of arena expansion. Arena expansion occurs when the emergence of international soft law in a new issue area creates an additional arena of political competition. For Newman and Posner, this is significant because it can disrupt existing power dynamics and work to shape the actors themselves. This happens as existing groups change their strategies and policy priorities to reorient to the new transnational arena. It can also lead to the creation or restructuring of institutions as new, transnational-level advocacy organizations and coalitions are formed.

After outlining these theoretical points in chapter 2, the rest of the book sets out to demonstrate them through a detailed tour of the post-Bretton Woods politics of financial regulation in the United States and Europe. Chapter 3 sets up the case studies by examining the origins and evolution of the contemporary international financial architecture. It analyzes the growth of financial soft law at the international level and its uneven development across the different subsectors of the industry. Significant here is the authors’ use of the historical institutionalist framework to demonstrate the key role played by existing institutional structures in the United States and other key markets. They also demonstrate how the creation of international soft law was, at times, deliberately used to influence domestic political contests over financial regulation.

Chapter 4 focuses on the legitimacy claims mechanism and uses it to explain the convergence of EU financial regulation toward the more market-oriented approach of the United States. In particular, it shows how international soft law was used to legitimize the position of regulatory factions seeking to reform EU financial regulation in the context of internal efforts to harmonize across member countries. As a side argument, the chapter also highlights the role that this convergence toward lighter-touch regulation played in the 2008 crisis.

Chapter 5 shifts the emphasis to the arena expansion mechanism and uses it to show how the 1988 Basel Accord helped transform the Institute of International Finance from a minor data organization into the financial sector’s premier transnational lobby group and the impact that this change had on other financial industry associations. This is a persuasive argument that reflects some of the key insights of historical institutionalism about how institutional structures and policies can work to constitute and reconstitute actors. It also serves to reinforce arguments made in the comparative federalism literature about the way that federal versus unitary systems give rise to different patterns of interest group aggregation, including the creation of subnational lobby groups and strategies. Thus, a key contribution of Voluntary Disruptions is in demonstrating how soft law can have a similar impact.

Chapter 6 shows how the presence or absence of international soft law explains variations in the degree of international coordination within post-2008 financial reforms in the United States. The specific focus is on differences that occurred across banking and derivatives regulation and the way that both the legitimacy claims and arena expansion mechanisms played a role. The conclusion sums up the book’s contributions and conducts an initial probe of the arguments in the domains of labor and environmental regulation.

Taken as a whole, Voluntary Disruptions covers a lot of ground on the politics of financial regulation and is very effective in demonstrating why international soft law matters in this domain and how its significance has increased over time. Particularly effective is the way that the authors carefully consider alternative explanations at the end of each chapter. That said, the cases also provoke a number of questions related to the legitimacy claims mechanism, causal significance, and the role of ideas.

In terms of the legitimacy claims mechanism, my first question is, How unique is international soft law compared to other forms of external or third-party validation that are often used by policy entrepreneurs? For example, business groups often use capital mobility and concerns over competitiveness with trade partners as a legitimacy claim to bolster their proposals for more pro-business tax and regulatory policies. In a similar fashion, progressive groups in the United States often use their country’s outlier status on issues such as public health care and gun control. So, is international soft law simply one of a number of potential legitimizing mechanisms, or does it have a more unique explanatory power? I am also curious about the extent to which international soft law is actually used compared to these other external validators, including various international norms.

Given these other potential validators, as well as the other resources possessed by policy entrepreneurs, my second question is about the ability to isolate international soft law and thus how to weigh its significance in different contexts. In the selected cases, the use of congruence analysis and process tracing works well, and as a result, I found the explanations of EU regulatory convergence and variations in US postcrisis financial regulation quite persuasive. However, the authors themselves note, “Our argument depends on an underlying level of competition among competing regulatory factions, which use international soft law to alter the balance among them. In those areas characterized by limited competition—because of weak domestic institutions or weak organization and mobilization of certain segments of the population—we do not expect soft law to have such far-ranging consequences. Future research will map these boundary conditions and consider how they do or do not apply across different policy domains” (pp. 166–67). Perhaps the authors could provide some further thoughts on where international soft law is likely to be most significant and on what some of the potential boundary conditions might be.

A final set of questions relates to the role of ideas. Does the written aspect of international soft law make it different from international norms in terms of facilitating legitimacy claims? Given that international soft laws can be portrayed as either modern and neutral or as elite and foreign, does their presence automatically benefit one regulatory faction over others, or is the ability to promote a specific framing equally important? To what extent does ideology determine the views of different regulatory factions on international soft law? Does international soft law have a progressive bias because it is international or a conservative bias because it is soft?

These questions aside, Voluntary Disruptions is a significant book that should be read by anyone interested in the politics of financial regulation, global economic governance, and historical institutionalist theory. Its theoretical applicability will no doubt extend well beyond the domain of financial regulation.