Modern slavery is widely regarded as a global problem of epic proportions. According to the 2021 Global Estimates, on any given day, there are 50 million people in situations of modern slavery, of whom 27.6 million are in forced labour and 22 million are in forced marriage. Despite the growth of a large web of antislavery laws and key political actors’ commitment to eradicating modern slavery, the number of slaves grew by 9.3 million people (about the population of Austria) between 2016 (the year the UN set a target to eliminate modern slavery by 2030) and 2021.Footnote ¹ Putting these figures into historical perspective, George Ramos, chief of staff of the Organisation for Economic Co-operation and Development (OECD), claimed that in 2015 the number of modern slaves in the world was ‘nearly four times the total number of Africans sold in the Americas during the four centuries of the transatlantic slave trade’.Footnote ²

These numbers are astonishing, and they help to explain why modern slavery has become a prominent issue on the global governance agenda.Footnote ³ Although there is a growing literature challenging these figures,Footnote ⁴ this book is not concerned with how many modern slaves there really are.Footnote ⁵ Instead, it focusses on law’s role in constructing modern slavery as a global problem. Modern slavery is an amalgam of legal concepts (including chattel slavery, forced labour, and human trafficking for labour exploitation and prostitution) defined in international law.Footnote ⁶ What unites these concepts is a shared characteristic – they are all forms of unfree labour: one person deprives ‘another person of their freedom for profit’.Footnote ⁷ This book explains how modern slavery’s legal expression – how it is defined in law, and the legal domains and jurisdictions to which it is assigned – shapes what we ‘see’ when we see modern slavery and how we go about getting rid of it.

The Legal Construction of Modern Slavery

This book provides a genealogy of modern slavery by tracing the evolution over time of its component legal concepts and how they came together under a single umbrella.Footnote ⁸ It grew out of my puzzlement with developments in the UK. When I moved there in 2013, I encountered a lively legal and political debate about how to define and combat modern slavery. In Canada, where I had been living and working, ‘modern slavery’ was used occasionally as a political rhetoric to vilify instances of exploitation. I was, however, familiar with the term ‘unfree labour’, used as an analytic concept for work relations in which direct physical, political, and legal compulsion is used to acquire and exploit labour.Footnote ⁹ In the UK, modern slavery became a quasi-legal concept with the enactment of the UK Modern Slavery Act, 2015. This act combines wide-ranging criminal prohibitions against human trafficking for sexual and labour exploitation with business regulations designed to create incentives for large transnational corporations to eliminate modern slavery in their businesses and supply chains.

I was curious about how modern slavery came to be the predominant legal lens for characterising unfree labour in the UK. I traced the origins of the UK’s Modern Slavery Act to the UN’s Protocol to Prevent, Suppress and Punish Trafficking in Persons Especially Women and Children against Trafficking in Persons, which was adopted in 2000 and came into effect in 2003. I turned to legal scholarship to identify the provenance of the legal concepts (such as human trafficking and forced labour) that comprise modern slavery. Doctrinal scholarship is concerned with identifying the key elements of different legal concepts – their history, interpretation, and application.Footnote ¹⁰ Legal scholars debate the ‘best’ interpretation of these concepts and how they fit together. Some claim that it is critical to place each concept in its appropriate legal domain because the legal context will influence the concept’s meaning and legal strategies.Footnote ¹¹ For example, some legal researchers argue that freedom from human trafficking should be treated as a human right, not simply a criminal prohibition.Footnote ¹²

Although doctrinal legal scholarship is essential for identifying the origins of modern slavery’s legal components and technicalities, it can’t explain why a specific definition was crafted or why it was lodged in one legal domain instead of another. To answer these questions, we must move from legal analysis to study the social world.

In the fields of political science, sociolegal studies, and sociology, scholars have shown that how the problem of modern slavery is framed influences the different legal domains (criminal, human rights, immigration, or labour law) selected to address it.Footnote ¹³ Frames are the mental structures we use to make sense of the world. They are the (often unconscious) constructs that shape the way we see the world; they tell us how different pieces of information connect, what is right and wrong, and how to make sense of this information and suggest solutions to correct perceived wrongs.Footnote ¹⁴

To understand how frames work, consider the sale of sexual services (prostitution) and human trafficking for sexual exploitation. For many people, the exchange of sexual services for money is an anathema; it is an essentially exploitative activity that undermines human dignity. Under this frame, the purchase and sale of sexual services should be banned by criminal law. But for other people, the gendered nature of commercial sexual services – the fact that most sellers are women and most purchasers men – reflects the sexual objectification and subordination of women. This ‘women’s equality’ frame treats prostitution as a form of violence against women, and the solution is to prohibit the purchase of sexual services. According to both these frames, prostitution is exploitation, and exploitation is a key element of the international definition of human trafficking. By contrast, some people (including many feminists) see the sale of sexual services as a livelihood strategy in the context of constrained choices; for this reason, the sale of sexual services should be regulated by labour law to prevent exploitation.

Laden with assumptions and meanings, frames are devices that help us select and categorise information and imbue it with moral significance. Thus, the literature on how societies frame modern slavery is critical for understanding how different forms of exploitation are conceptualised within public policy and how this influences what is considered to be the appropriate legal response. This literature is also useful for unpacking the social, economic, and political relations that result in specific legal strategies.

There is also a lively debate about the political work that the concept of ‘modern slavery’ performs. Annie Bunting and Joel Quirk argue that it harnesses the moral outrage once associated with the transatlantic slave trade and directs it at ‘an unstable amalgamation of a wide range of diverse practices that go well beyond both legal definition and historical experiences of slavery’.Footnote ¹⁵ Researchers have shown that antislavery rhetoric is a ‘powerful lodestone’ for competing interests that potentially align with other ideological, political, and economic agendas.Footnote ¹⁶ Antislavery rhetoric has been used to support a conservative moral approach to commercial sex, stronger border and immigration controls, and a national security agenda that emphasises borders and policing.Footnote ¹⁷

Others point out that ‘modern slavery’ has been used to focus attention on labour exploitation and to support forms of labour regulation.Footnote ¹⁸ Some researchers dig deeper to investigate the ‘traditions of thought, conceptual schema, and collective memories’ that frame the very idea of modern slavery.Footnote ¹⁹ They question whether the term ‘modern slavery’ should be used at all. Lyndsey Beutin, for example, argues that the concept’s rhetoric and imagery functions as a racial mnemonic ‘to circumvent historical Western responsibility for racial chattel slavery’.Footnote ²⁰

I draw on the critical modern slavery literature to place key legal concepts in their cultural, political, and economic context and to trace their use and evolution over time. I bring the legal and social-political literature into conversation to show how social and political context shapes legal meaning and how legal concepts and technicalities, in turn, shape how we see our world. Since the relationship between the social and the legal is recursive and co-evolving, this dual approach is necessary for understanding why antislavery laws and policies have risen on the political agenda and the broader governance work they do.

‘Modern slavery’ covers a wide range of different kinds of exploitation, including sex trafficking, child sex trafficking, forced labour, forced marriage, the compelled sale of organs and body parts, debt bondage, domestic servitude, forced child labour, and the unlawful recruitment and use of child labour. I focus on a subset of modern slavery – forms of unfree labour associated with international labour migration and transnational supply chains – for two reasons. To offer insight into the relationship between unfree labour and capitalism, on the one hand, and to explore how sovereignty is being reconfigured, on the other.

Unfree Labour and Transnational Law

The discovery of modern slavery as a global problem both coincided with and reinvigorated debates about how to conceptualise unfree labour in relation to capitalism. Historically associated with precapitalist forms of economic organisation, unfree forms of labour (such as chattel slavery, indenture, debt bondage, and servitude) were regarded as the antithesis of free wage labour.Footnote ²¹ According to prevailing economic wisdom, unfree labour was supposed to disappear as capitalism deepened and expanded. Recently, however, unfree forms of labour have attracted increasing attention as neoliberal policy regimes, which promote labour flexibility and see the market as the key governance mechanism, have become embedded across the globe.Footnote ²² The persistence and proliferation of unfree forms of labour across developed, emerging, and developing countries has been linked to different aspects of contemporary globalisation – dispossession through war, ecological degradation, structural adjustment policies, transnational criminal activity, international migration, neoliberal capitalism, and state corruption and the breakdown of the rule of law.Footnote ²³ By investigating attempts to address forms of unfree labour linked to international migration and global supply chains, I reveal the extent to which antislavery initiatives are linked to the fading legitimacy of contemporary neoliberal capitalism.Footnote ²⁴

Modern slavery involving migrant workers and supply chains is a transnational problem because it crosses national borders. But nation-states lack the legal authority – the jurisdiction – to deal with it. International law supports national sovereignty and frames it in territorial terms.Footnote ²⁵ A state has jurisdiction, the authority to exercise legal power, over its territory.Footnote ²⁶ Initiatives to combat unfree labour linked to transnational processes do not fit with territorial understandings of jurisdiction tied to the territory of the nation-state. Consequently, a thick web of international, regional, national, and local legal instruments, policies, techniques, and practices has been fabricated to eradicate the ‘global’ problem of modern slavery.Footnote ²⁷ An antislavery network composed of key states, advocacy groups, nongovernmental organisations, faith groups, trade unions, transnational corporations and their charitable foundations, and national, international, and supranational institutions and organisations grew alongside it. This network advocates using a wide variety of legal approaches and instruments to tackle modern slavery, including criminal, immigration, human rights, labour, and business law.Footnote ²⁸

In this context, the nation-state, which used to be the primary actor, is now but one among an assemblage of actors, what I call the ‘global antislavery governance network’. Terrance Halliday and Gregory Shaffer’s processual conception of transnational law is useful for understanding this multiscalar network and the web of antislavery laws it has generated. Their approach places ‘processes of local, national, international, and transnational public and private lawmaking and practice in dynamic tension within a single analytic’.Footnote ²⁹ In doing so, it offers a way to distinguish law from other forms of social ordering by emphasising law’s distinctive institutions (courts, legislatures, agencies, tribunals, and executive departments) and forms (statutes, regulations, codes, case law, treaties, model laws, and court decisions) and its alignment with state and juridical-sovereign power.Footnote ³⁰ Halliday and Shaffer’s approach also captures the multiscalar dimension of transnational law since the institutions and organisations involved in its production must ‘transcend or span’ the nation-state, even though the approach recognises that these laws are generally directed at the nation-state since national sovereignty continues to be accepted as the predominant form of legitimate authority.

Modern slavery laws exemplify transnational law since they combine international, national, and sometimes regional laws.Footnote ³¹ To make sense of this tangle, I provide case studies of what can be called ‘transnational modern slavery law’.Footnote ³² I selected five cases because they involve the international laws upon which the concept of modern slavery is based, they include key actors in the global antislavery governance network, they illustrate the scalar interaction of transnational law, and they exemplify different approaches to combatting modern slavery.

Three chapters focus on the international scale. Chapter 1 describes how the UN and United States developed an international criminal-law instrument to define human trafficking, subsequent attempts by US administrations to pin down the meaning of human trafficking, and the development of a multifaceted approach to the problem. Chapter 2 examines how Walk Free, a private foundation, has become a key global governance actor by producing knowledge about modern slavery and promoting business-led forms of governance to eliminate it from global supply chains. Chapter 3 investigates how the International Labour Organization (ILO) used its jurisdiction over forced labour to stake a claim in the global antitrafficking assemblage and to steer global antislavery policy away from criminal and immigration law towards labour and human rights. Shifting from the international scale, Chapter 4 studies the European Union (EU), a site of multiscalar governance that has led the way in adopting binding, region-wide legal norms to address human trafficking. These norms augment the human rights of victims and fill the gap surrounding victim protection left in the UN’s Human Trafficking Protocol.

Chapters 5 and 6 focus on the United Kingdom to provide an in-depth account of how antislavery governance strategies involving transnational forms of unfree labour have changed over time at the national scale. Although international and transnational legal instruments define the main legal categories of unfree labour, nation-states must implement them and give them meaning. As antitrafficking scholar Kiril Sharapov notes, ‘The role of national framing contexts and of larger frameworks of neoliberal movements of labour, resources, and capital globally remain largely unacknowledged within official antitrafficking discourses.’Footnote ³³ As this book shows, how a country filters international norms and approaches through its distinctive cultural political economy shapes its governance strategy.Footnote ³⁴ I focus on the UK for several reasons: it was the first country to enact a modern slavery law that combined criminal law with business regulation; as a member of the EU until early 2020, it was embedded in a multiscalar legal regime governing human trafficking; and it is a prominent member of the global antislavery governance network.

Jurisdiction Matters

When it comes to transnational law and modern slavery, jurisdiction matters. ‘Jurisdiction’ in this context is not simply a technical question concerned with whether a particular sovereign state or judicial or quasi-judicial body can exercise legal authority over a territory, dispute, person, or issue.Footnote ³⁵ Rather, the transnational legal governance of modern slavery demands a multidimensional understanding of jurisdiction. The scalar dimension of jurisdiction is the most familiar. Take federal states, for example, where jurisdiction operates to determine which level of government has authority over a particular matter. The treaties that make up the EU also allocate competences (governance authority) on a scalar basis between EU institutions and Member States. But ‘jurisdiction’ has another important meaning: it refers to the power of the law to act and the scope of a legal institution’s authority in relation to other institutions.Footnote ³⁶ This is the governance dimension of jurisdiction. By combining the governance and scalar dimensions of jurisdiction, Marianna Valverde treats jurisdiction as a complex legal assemblage that operates as a kind of sorting mechanism that allocates a problem – a particular form of unfree labour, for example – to an authority for resolution.Footnote ³⁷ Jurisdiction establishes which state has legal authority over a particular issue, whether the delegation of authority to other systems and apparatuses is lawful or unlawful, and which of the different subsystems or domains within a legal system and its institutions (a criminal court, or human-rights tribunal, for example) has authority over a specific matter.Footnote ³⁸

Modern legal systems are a quilt of different legal domains, such as criminal law, commercial law, and constitutional law. Each legal domain involves assumptions about the nature and causes of a problem and the goals, strategies, and techniques for governing it, including burden of proof, remedies, operatives, and forms and processes of adjudication and dispute resolution.Footnote ³⁹ By assigning a subject to one of the legal domains that makes up a legal system, jurisdiction settles the political question of how a problem is to be resolved. If, for example, human trafficking is seen primarily as a problem of criminal activity, then the criminal-law jurisdiction is set in motion. Criminal law is replete with its own focus (the guilt or innocence of the perpetrator), principles (innocent until proven guilty), precepts (proof beyond reasonable doubt), technicalities (rules of evidence), and officials (police, prosecutors, and courts) with a range of powers (search, arrest, confiscation of assets). By contrast, if human trafficking is regarded primarily as a matter of human rights, the institutional goals and practices of that legal domain are quite different from those of the criminal law. The goal of human-rights law is to safeguard the rights of victims of trafficking from infringement by state policies and practices. The prevailing principle or legal norm is to preserve human dignity, and states are required to develop mechanisms to identify victims and offer them redress. The relevant institutions are human-rights agencies and tribunals that exercise administrative powers. The legal assemblage of jurisdiction operates as a sorting mechanism that allocates a problem – a particular form of unfree labour, for example – to an authority for resolution and keeps the different domains from clashing.Footnote ⁴⁰

The assignment of jurisdiction over a social problem means that questions about the nature of the problem or how best to deal with it are no longer relevant.Footnote ⁴¹ Once human trafficking is assigned to the criminal law, the political contest over the goals and techniques of governance is transformed into an ‘apolitical’ process of sorting subjects into legal categories such as ‘victim of trafficking’ or ‘smuggled migrant’. Ascertaining the appropriate jurisdiction becomes habitual and path-dependent; in the process, jurisdictional questions are classified as simply ‘technical’. Legal officials draw the borders between different legal categories such as ‘victims of trafficking’ and ‘illegal migrant’, and, in turn, these categories come to be seen by ordinary people as common sense and, as such, come to be used to describe the people to whom the legal categories apply.Footnote ⁴² In this way, legal categories help to construct what we see as unfree labour.

Jurisdiction also resolves scalar questions about which institution – international, transnational, nation-state, or subcomponent of a nation-state – has authority. The scalar dimension of jurisdiction can also operate as a technique of governance: one that challenges territorial notions of national sovereignty. Increasingly, states must negotiate with various other agents (such as local governments, international institutions, and transnational corporations that wield power) and other sources of law to retain or exercise sovereignty. This partial detachment of authority from territory – or deterritorialisation – requires private actors to enforce border and immigration control.Footnote ⁴³ Saskia Sassen points to trade and investment treaties as a ‘new type of bordering’ that allow ‘firms and markets to move across conventional borders with the guarantee of multiple protections as they enter national territories’.Footnote ⁴⁴ What international trade and investment law does is allow firms to rescale, to shift from national to international law, to enforce contracts. But nations have no similar recourse should contractual terms end up harming workers or being unfavourable to the socioeconomic interests of their citizens.Footnote ⁴⁵ States in the Global North have begun to respond to this jurisdictional conundrum by enacting laws that require large transnational corporations to exercise due diligence to keep their global supply chains free of modern slavery. In this way, states use corporations residing in their territorial jurisdiction to extend legal norms beyond their territory. This rescaling is part of the game of jurisdiction, in which states, the EU, and corporations seek to manipulate the law to their advantage.Footnote ⁴⁶ Approaching scale in this way helps to illuminate how processes of globalisation reconfigure rather than simply weaken state sovereignty.Footnote ⁴⁷

Understanding jurisdiction as an assemblage enables us to see how jurisdiction can be ‘unbound’ from territory.Footnote ⁴⁸ One implication of states using transnational corporations as a ‘territorial extension’ of their jurisdiction is, as Nico Krisch notes, the possiblity for multiple states to have valid claims to have jurisdiction over an issue without an established legal method for resolving which should prevail.Footnote ⁴⁹ In such cases, the exercise of jurisdiction ‘depends above all on states’ political, institutional weight’, exacerbating power inequalities that were forged as capitalism advanced along with European imperialism.Footnote ⁵⁰ The result is that the jurisdictional claims of some states matter more than others.

Questions and Approach

This book argues that modern slavery laws are a response to global capitalism, which undermines the traditional understandings of the distinction between free and unfree labour and poses intense challenges to state sovereignty. Instead of being a solution to the problem of labour exploitation, modern slavery laws divert attention from the underlying structures and processes that generate exploitation in the first place. Despite the best efforts of academics, advocates, and policymakers to develop a truly multifaceted approach to modern slavery, it is difficult to dislodge modern slavery initiatives from the domains of criminal and immigration law and uncouple them from the conservative moral and economic agendas with which antislavery initiatives are aligned. The problem with the concept of modern slavery, as Julia O’Connell-Davidson shows, is that it provides a ‘highly selective lens through which to view restraints on human freedom’.Footnote ⁵¹

How did modern slavery emerge on the global political agenda? Where do key actors in the global antislavery network draw the boundary between free and unfree labour? How does the multifaceted approach to modern slavery keep the different legal domains to which unfree labour is assigned from clashing? How do attempts to govern transnational forms of unfree labour reconfigure sovereignty? The book answers these questions by crafting a genealogy of modern slavery based on secondary sources, primary legal and policy documents, government documents, media accounts, grey literature, advocacy material, websites, and key informant interviews. Its case studies cover a period of just over twenty-five years, from the late 1990s, when human trafficking was identified as a global problem requiring international action, to September 2023. I conclude by summarising the book’s main arguments and considering the vexed problem: What makes labour free?