Walter F. Baber and Robert V. Bartlett’s Consensus and Global Environmental Governance is the final book in a three-part series about the development of Earth system governance. Where the two previous books introduce and describe the authors’ prescription for juristic democracy in global environmental governance, this book confronts powerful objections and forwards specific advantages of a deliberative democratic approach. The overall vision is to have a sufficient number of globally representative juries engage in collective will formation, by ruling on the same hypothetical cases and then aggregating those decisions into a global system of common law. This final book focuses on the concept of consensus: why it is possible and good, and how to achieve it. Key foils include alternate systems of governance: majoritarianism, technocracy, and state sovereignty. Baber and Bartlett believe that “rational governance” (p. xiv) can best be achieved through global-scale democratic deliberation.

For Baber and Bartlett, the fundamental problem with existing global governance is the “democratic deficit” (p. xii). The main advantage of a deliberative approach is that democracy produces legitimacy, which makes rule systems politically sustainable and is therefore a key condition for effectiveness. The book connects iterative and small-scale juristic democracy to the development of a global system of common law through the development and aggregation of consensus, or “collective will formation.” Baber and Bartlett draw from both legal theory and the social sciences; their proposed mechanism for mapping and aggregating “considered opinions” combines the method of content analysis with the practice of “restatement” from the common law tradition.

What happens to the resulting body of constructed legal norms and principles is not entirely clear. In chapter 3, it is the “raw material for a process of codification” (p. 47) through traditional international negotiation. In chapter 8, juristic democracy supplements administrative discretion with “rule making via hypotheticals” (p. 148), as an alternative to case-by-case adjudication. In chapter 9, it provides a stock of principles upon which international tribunals can draw, “a substitute for the stare decisis doctrine” (p. 168). The broad utility of the consensus drawn from citizen juries can thus leave the reader with a sense of incompleteness; the starting point is described in great detail, but the finish line of rule making and implementation remains obscure.

Consensus and Global Environmental Governance is an important resource for theorists and architects of Earth system governance. It provides a modular and concrete mechanism for global decision-making that builds legitimacy into the process via the mechanism of citizen juries. The literature on jury size and jury-style deliberation is surveyed in great detail, and the ability of juries to make rational, representative decisions is well defended. But the book would benefit from acknowledging a key difference between trial and citizen juries: the former interpret the rules of a pre-existing legal order, whereas the latter develop principles and norms to serve as the basis of a new common law. Many of the same findings regarding group dynamics and diversity probably apply in either case, but the problem structure and decision-making tasks are different. Can citizen juries generate consensus norms that successfully confront complex environmental problems? Baber and Bartlett suggest that any problem can be simplified and explained by expert witnesses, just as issues are in court. If juries are to produce “ecological rationality,” “ecological sustainability,” and “ecological democracy,” then they will need to understand ecological systems. But is the opinion of a forensic scientist or the guidance of a judge really comparable to the explanation of an ecologist, climatologist, or oceanographer? Baber and Bartlett do not address this issue, because for them effectiveness is more about the provenance of a decision than its specific content.

A key advantage of juristic democracy is its ability to avoid or neutralize biases in decision-making. Baber and Bartlett lambast the arguments of “difference democrats,” or those who assert that deliberation and the requirement of “public reason” are hostile to diversity. A recurring rejoinder is the argument that researchers can compose specific juries—either representative or “enclave”—to address the risk that decisions will reinforce existing social and economic power relations. But there are other features of juristic democracy that seem to assume neutrality, instead of achieving it by design. Cases drafted by “the social scientist or environmental governance professional” (p. 25) must be “properly structured” to be “directly analogous” to real-world situations and as concrete as possible, while remaining hypothetical. Baber and Bartlett provide no guidance for evaluating whether a constructed case is valid as a test of the competing positions, except to say that repeated deliberations with slightly varied cases can help determine which aspects of a case explain deliberative outcomes. Juries will be provided with “well-balanced information” that is “grounded in reliable research and valid inference,” and also “the arguments of actual stakeholders” (pp 47, 25). But what happens when the arguments of actual stakeholders rely on unreliable research? And who determines what is “balanced” or who is a “stakeholder”? These important questions, and who answers them, may impact how democratic the deliberation of citizen juries really is. Baber and Bartlett offer three general solutions—transparency, peer review, and “a diverse set of disinterested deliberators” (p. 137)—but do not apply them to these specific requirements.

Baber and Bartlett demonstrate that their proposed system of Earth system governance is desirable. But the book does not establish that global juristic democracy is plausible. The authors suggest that the “inherent democratic legitimacy” of their method would “bypass states” and create a new rule-making system “fully complementary with other governance approaches and strategies” (p. xv). Environmental problems would be treated as questions of distributive justice, potentially rebalancing international political advantages. But Baber and Bartlett do not acknowledge or answer arguments about the durability of great power politics in this book, and the result is a proposal that appears more idealistic than it really is.