In Vigilantes beyond Borders, Mette Eilstrup-Sangiovanni and J. C. Sharman posit that the role of international nongovernmental organizations (NGOs) in enforcing international law has yet to be fully recognized. As its title indicates, the book is part of a body of literature highlighting the role of NGOs as influential global actors, a tradition kicked off a quarter century ago by the pathbreaking book Activists beyond Borders (1998) by Margaret Keck and Kathryn Sikkink. Eilstrup-Sangiovanni and Sharman follow in their path by telling a similar story of expanding NGO power in global governance. But while prior studies have primarily emphasized how NGOs raise awareness and shape global governance arrangements, this book elaborates on the growing appetite among many NGOs to embrace enforcement activities. Eilstrup-Sangiovanni and Sharman convincingly argue that NGOs have more recently expanded from limited roles of being lobbyists and advocates to engage in direct interventions designed to end wrongdoing. This book offers a compelling and essential narrative about the ongoing evolution of NGO activism and the expansion of NGO roles in global governance.

Eilstrup-Sangiovanni and Sharman recast many well-known NGO activities as increasingly focused on the enforcement of international law. According to the book, existing scholarship has often mislabeled NGO activities, such as patrolling, surveillance, guarding, evidence gathering, investigating, and giving testimony, as “mere” advocacy (p. 10). However, the authors argue, such actions should really be viewed as part of the “soft, investigative end of the enforcement spectrum,” alongside other, more “hard” law-enforcement efforts, such as preserving evidence, arrests, and litigation (pp. 28–29). And while Eilstrup-Sangiovanni and Sharman acknowledge that private law enforcement is not new, they argue that it has grown in scale and has become distinctly transnational in nature (p. 5).

Before reviewing the evidence for expanded NGO enforcement activities, the book defines in chapter 1 key terms and concepts. “Enforcement” is defined as “compelling compliance” (p. 17) in areas where established law exists but is insufficiently respected. “Vigilantes” are nonstate actors engaging in enforcement activities and doing so wholly independent from states (p. 18). They neither act on behalf of governments nor establish and enforce their own laws. Instead, they use their enforcement activities to pressure governments and corporations to comply with existing international law. For example, human rights NGOs may use domestic or international courts to advance criminal complaints against human rights violators, or environmental NGOs may use drone technology to detect and counteract poaching activities.

Why has there been an expansion of NGO enforcement activities in recent decades, especially in the areas of environmental, human rights, and anti-corruption policy domains? The book first elaborates on the demand- and supply-side causes. On the demand side, there is a growing enforcement gap due to a proliferation of international agreements with weak-to-nonexistent enforcement mechanisms (pp. 32–34). The book shows how governments have created a growing number of global agreements to manage cross-border issues but have invested relatively few resources into enforcement activities. For example, international law has greatly expanded the protection of biodiversity, but the multitude of existing treaties lack significant enforcement capabilities (pp. 87–89). This growth in international conventions creates two complementary effects: the lack of enforcement creates demand for NGOs to step in, while the growth in international agreements and courts gives NGOs more venues in which to engage in their enforcement activities (pp. 34–38). Second, on the supply side, NGOs benefit from technological advances facilitating surveillance, cross-border communications, and big-data analytical capacities (pp. 38–40). Finally, the overall growth of NGO sectors worldwide has increased competition and pushed groups to innovate and seek out organizational “niches,” including moving into enforcement activities (pp. 40–45).

Across three policy domains—human rights, the environment, and corruption—the authors trace changes in demand- and supply-side factors and provide illustrative examples of NGO enforcement activities. Courts and evolving technologies emerge as central venues and tools across all three domains. There is also evidence of cross-fertilization across the three domains, including using human rights law to address the climate crisis (pp. 94–96). Vigilantism is a common trend across policy domains, but it takes on unique and varied forms in different contexts (pp. 161–64). For example, direct actions are more common among environmental groups but are rarely part of the strategic portfolio for human rights or anti-corruption NGOs. Environmental vigilantes also typically target companies and governments, while their human rights and anti-corruption peers typically target individuals.

Relying on a range of web-based sources, news reports, and forty-six interviews, primarily with activists (pp. 193–94), the three empirical chapters introduce readers to key NGO vigilante groups and their activities. This includes descriptions of how these actors take advantage of expanding opportunities for data gathering and sharing to engage in more “decentralized enforcement” that complements more traditional uses of collecting evidence for “naming and shaming” efforts (p. 108). These technological advances have given rise to a new crop of specialized NGOs, including Earth League International in the United States, which exposes environmental crimes, SkyTruth in the United States, which is dedicated to monitoring the world's oceans, EAGLE in Cameroon, which focuses on arresting poachers on the African continent, and eyeWitness in the United Kingdom, which collects visual evidence of atrocities.

Is this book, then, evidence for the ever-growing power of NGOs and their expanding roles in global governance? And is the future of international law increasingly dependent on decentralized NGO enforcement? The authors take on these important questions in the final chapter. Here, they portray NGOs as providers of a public good, strengthening international law “from below” and contributing to deterring future offenses as well as pressuring governments to engage in their own enforcement activities. The authors also claim that NGO enforcement is essential in cases where governments are unable, rather than unwilling, to enforce effectively themselves (p. 180). Since these NGOs only enforce what is already settled international law, their actions are legitimate even if they are not acting as representatives of specific populations, like governments do (p. 185). The authors do acknowledge a few potential downsides of NGO enforcement, including a possible decline in state enforcement efforts, the reluctance of states to adopt and sign international treaties in the future (p. 181), and the rise of “amateurs” engaging in “reckless” enforcement activities (p. 184). They argue that the overall benefits outweigh these possible problems because the main alternative to NGO enforcement activities is “no enforcement at all” (p. 183).

A more critical reading of the book's narrative starts with questioning how these groups are often collectively hailed as moral leaders allegedly “speaking truth to power.” Vigilantes beyond Borders perpetuates a narrative emphasizing the traditional view that (typically Western-based) NGOs are always “doing good” and individuals, governments, or businesses (often based in the Global South) are the “bad guys.” A vast majority of the prominently featured vigilante NGOs in the book are based in the United States, the United Kingdom, or other industrialized countries. And many of the technologies they deploy, to apparent great effect, are supplied by global corporations and have faced popular backlash, including questions about the ethics of using widespread surveillance and data-gathering techniques. The book reproduces the idea of moral superiority of mostly Western-based NGOs, even though the same sector has faced persistent charges of “white saviorism,” toxic organizational cultures, and a lack of attention to local or indigenous voices.

Especially in the environmental area, there are longstanding concerns about NGOs using violent means against local populations. For example, in 2016 the NGO Survival International filed a complaint against the World Wide Fund for Nature (WWF) alleging that the environmental group had abused indigenous groups in Cameroon as part of its anti-poaching efforts. This dark side of the NGO world deserved much greater attention, especially as some of the “new” power of these groups relies on highly contested commercial technologies. The book stands in a tradition of taking for granted the good intentions of activists, while not taking seriously the structural global inequities and problematic technological assumptions shaping many of their actions. While the book provides important insights into expanded NGO roles and powers, it does not engage with the more fundamental question of whether NGOs must first transform themselves before they can credibly claim to transform the world around them.