A substantial body of work examines the conditions under which states commit to and abide by human rights and the laws of war, but we know considerably less about civil conflicts than international ones and less about rebel groups' adherence than we do governments'. Professor Hyeran Jo's book, Compliant Rebels, seeks to fill this gap. It asks, “Why do rebels comply with international norms and laws during civil war?” The answer to this question (together with the answer to the same question for governments) has critically important implications. It may ultimately help minimize civilian suffering in civil wars, encourage practices that more closely conform to the ideals contained in international humanitarian law (IHL), and it could help humanitarian-minded organizations and governments to more effectively allocate their scarce resources to affect change.

So, among rebels, who complies? Jo argues that a certain category of rebel organization, the “legitimacy-seeking” type, is more likely to abide by IHL than the other “legitimacy indifferent” type. Legitimacy-seeking rebels have a domestic and international constituency that supports the norms enshrined in IHL and so, for principally strategic reasons, will more likely comply with its rules. Legitimacy-seeking rebels have three characteristics in common: 1) they have an active [legal] political wing, 2) they have secessionist ambitions, and 3) they have a “human rights-conscious” foreign government benefactor (pp. 94–100). Legitimacy indifferent rebels, in contrast, “have little to no motivation to appeal to domestic and international constituencies” (p. 52). After setting out this argument, the book quantitatively examines legitimacy-seeking rebels’ propensity to comply with three humanitarian laws: against the purposeful killing of civilians, against the use of child soldiers, and in favor of access to prisoners of war by the Red Cross (ICRC). Case vignettes are included alongside each large-N analysis to illustrate the mechanism connecting legitimacy-seeking motives to those rebels' compliance. The book concludes with historical and contemporary cases of rebellion and then makes recommendations for policies following from its principal findings.

Insofar as causality is concerned, this is a thorny subject. Norm compliance, a classic non-event, has bedeviled scholars for decades. So the question motivating this book is a very good one. Unfortunately, this reader remains stubbornly unconvinced that rebels’ drive for legitimacy is at the root of their lawful wartime behavior.

The book’s primary limit is that it lacks a theory of civil war to support its hypotheses. Five guiding assumptions about rebels are provided, (e.g.: that they fight for political ends, that compliance is costly, etc.) but the book does not provide a compelling reason why it is usually in rebels' best interest to violate humanitarian laws. Humanitarian laws exist because state leaders agreed that the outlawed practices were generally not required or desirable in war. Why is it ceteris paribus militarily advantageous for rebels to engage in the one-sided killing of civilians? Ought rebels be regularly, purposively killing civilians if they hope to win? What level of killing should we expect? Additionally, some of the conflicts in the project data are killing tens of thousands (Russia—Chechnya) while others are just surpassing 25 annual battle related deaths (Britain—Real IRA). Civilian killing seems much more likely in the former. In the latter, would child soldiers be desirable? Would the rebels hold prisoners? Would the ICRC request visits if no prisoners are held? In short, the nature of the conflict and scale of its violence seem important, and yet they are overlooked.

Therefore, it is unclear that rebel compliance is really “a puzzle.” To illustrate, take the assumption that compliance is costly for rebels. Pages 91–92 report that 51% of rebel groups did not engage in any one-sided killing of civilians (>25 purposive killings in one year) during their wars. Indeed, where temporal data on civilian killing is presented in Appendix 3, it appears that most rebels are complying with IHL most of the time. The book concludes that these “persistent compliers” weighed the costs of not killing against the benefits of legitimacy and legitimacy concerns won-out. But when a rule is internalized, compliance is not considered in terms of the ‘logic of consequence,' but via the ‘logic of appropriateness.' Therefore, it is just as reasonable to conclude that, for the majority of rebels, compliance is costless because they do not consider slaughtering civilians to begin with. The so-called “switchover” compliers (and switchover non-compliers) seem to hold the most important evidence of the book's argument, but are not tested quantitatively.

While the book marshals an impressive array of data to support its claims, some of the modeling choices also limit the book's findings. For example, legitimacy-seeker qualification number three (above) seems as likely to be a result of the character of the organization's wartime actions as a cause (and a similar problem may arise with qualification 1). Would be sponsors with a strong IHL commitment should be more likely to offer support to those already complying with IHL. The logic underlying the qualification is similarly unclear. If a rebel group has an external sponsor with a vibrant humanitarian law constituency, then it follows that it has an incentive to comply with IHL. But rebels without a sponsor might also want one, and following IHL should be more likely to get them one with an active, domestic IHL constituency. Wouldn’t these groups be legitimacy-seekers too?

Further, with respect to child soldiering, the book employs the higher, more controversial age of 18 in the Optional Protocol to the Convention on the Rights of the Child (CRC) rather than the universally accepted 15, but does not explain this choice or code the alternative. In the analysis of child soldiers, secessionists are also curiously argued to be more likely to violate IHL than other types of rebels because they have domestic legitimacy. This logic suggests that secessionist child soldiers are more likely volunteers than conscripts, but does not help us to understand why children would be systematically more likely to be used in secessionist conflicts than in others. And when examining child soldiering, the analysis appears to select on a “legally allowed political wing,” dropping over half of the observations from the data. These choices have important consequences for what kinds of inferences we are able to draw from the analyses and should be explained.

In sum, this book addresses an important topic with many potentially significant policy implications. It certainly delivers a provocative initial explanation for rebels’ humanitarian impulses in civil war. I have questions about its analysis. Given the sensitive subject matter, the paucity of good data, and the complexities involved in examining the causal power of norms, the modeling decisions should be given special care. At the same time, as a first foray into an important, inherently difficult subject matter, it will surely be widely read and debated by scholars and practitioners with interests in advancing humanitarian law.