In this chapter, I introduce the main questions I seek to answer in this book, which are: what gives international courts the authority to punish individuals for international crimes, and under what conditions may courts legitimately exercise that authority? I give an overview of the history of international criminal justice, of my methodological assumptions, and of the arguments I make in the individual chapters.

The introduction outlines the conventional narrative that this book seeks to question: The idea that the allocation of the legal right to wage war only to sovereign states, penned by a humanitarianly minded Gentili and implemented in practice through the seventeenth century, became one of the core stabilizing factors of the new states-system in the aftermath of the cataclysmic Wars of Religion. It then lays out the book’s core argument along with its stakes for contemporary debates about the regulation of warfare in the international order.

This concluding chapter sums up the key findings of the book before reflecting on the costs involved in remaining welded to the old, conventional story of Gentili, the state, and “modern” war.

Chapter 3 traces the historical origins and evolution of legal debates on the ‘protection of the environment in relation to armed conflict’. It examines legal developments and interpretive efforts of scholars to expand the reach of the traditional jus in bello to account for conflict-related environmental degradation and ‘illegal’ resource exploitation, until the more recent attempts to look beyond the laws of armed conflict and war crimes into IEL and HRL. By charting the different formulations of environmental destruction/exploitation in rules governing war, this chapter sheds light on the changing ideas on the relationship between nature, conflict, and humanity, and the problems/possibilities with ongoing conversations in the field.

Grotius' two major treatises on the law of nations - De jure praedae and De jure belli ac pacis - both had the discussion of the just war doctrine as the backbone to their structure and argument. Whereas the older treatise was construed to argue the justice and legality of the taking of a Portuguese ship in East Indian waters, the more mature work aimed at a systematic exposition of the laws regulating the starting, waging and ending of war. Grotius offered a novel reading of the just war doctrine by rewriting it into the key of his general legal theory and his doctrine of natural rights as subjective rights under commutative justice. This chapter analyses Grotius' reframing o the just war doctrine and his re-systematisation of late-medieval and Renaissance legacies of theologians, canonists and civilians into a new doctrine of jus ad bellum, also giving some attention to its effect for the legal process of peace-making.

Grotius lived through a time of great upheaval in Europe as well as in his country of birth, the Dutch Republic. The religious, political and constitutional convulsions that struck the Republic destroyed Grotius' career but also, in combination with fundamental changes in the intellectual outlook of early seventeenth-century Europe formed his views of God, nature, society, politics and law. This chapter introduces the extraordinary polymath Grotius was from the perspective of this background and offers a map to the five parts of this volume, and their respective chapters.

This chapter explores the political, social, and economic conditions that have shaped the turn to history since the 1990s. Those conditions include the break-up of the Soviet Union and the ‘end of history’ narrative that accompanied a decade of ambitious liberal expansionism, the crisis of liberal internationalism triggered by the war on terror and the financial, energy, food, asylum, and climate crises of the early twenty-first century, and the shift in geopolitics caused by the rise of the BRICS and particularly of China as an economic power. International lawyers in practice and the academy have drawn on past events, practices, records, and cases as argumentative resources in adjudicatory settings and in broader debates over how to understand, justify, or resist the transformation of international law. The turn to history eventually began to be understood as a project that should be distanced from the argumentative practice of international law and measured against the empiricist protocols of academic historians. This chapter returns it to the context of international legal argumentation from which it arose, in order to gain a better understanding of the turn to history as an intervention in present struggles over the meaning of international law.

This concluding chapter argues that the interplay between international law and empiricist history has served to offer a new grounding for formalism in an extremely fraught political context. Historical work is increasingly relied upon as a source of substantive claims about what law really means and of scientific methods for studying the past. Lawyers rely on the scientific tone and resulting truth effects of accounts presented by professional historians to intervene in contemporary debates by using the claims made in those narratives about international law’s ‘true’ origins or ‘real’ history. Appeals to contextualist histories allow lawyers to present their arguments as being grounded on evidence and to characterise the other side in a legal debate as ideologically motivated, presentist, or engaged in myth-making rather than proper scholarship. The chapter argues that international lawyers cannot look to historians (or anyone else for that matter) to save the day with impartial and verifiable evidence-based interpretations of what international law really is, means, or stands for. What then is to be done? The chapter concludes by exploring why and how we might study the international legal past even knowing that writing histories of international law is inevitably a partisan act.

This chapter argues that contemporary claims about what empiricist history can offer international law are part of a longer tradition. A particular vision of law and figure of the lawyer have been central to claims made by empiricist historians of political thought for at least a century. The chapter focuses on four influential scholars whose work has influenced the method debates in international law – Herbert Butterfield, JGO Pocock, Quentin Skinner, and Ian Hunter. It traces the figure of the lawyer as apologist for power that reappears in their texts and against which their historicizing methods are staged. While the figure of the lawyer appears in different guises – as Whig constitutionalist for Butterfield, English common lawyer for Pocock, Italian scholastic lawyer for Skinner, and Prussian natural lawyer for Hunter – in each narrative the lawyer functions as the foil for a new heroic figure. That figure, the historicizing humanist, arrives on the scene to offer an anti-metaphysical challenge to the oppressive authority of received tradition. This chapter situates debates over the turn to method in international law within that longer story, in which historians are able to take up their preordained place as radical disrupters of orthodoxy.

This chapter challenges the representations of international law that dominate the turn to history. The vision of international law as metaphysically grounded and of lawyers as scholastics or moralising judges is resonant because it shores up a familiar fantasy. Yet that vision bears little relation to the ways in which contemporary international lawyers use the past in the practice of making legal arguments. This chapter explores the indeterminacy and capaciousness of the past materials out of which international legal arguments are assembled and the varied roles lawyers are trained to adopt in making such arguments. It shows that international lawyers are already immersed in a centuries-long debate over the grounds of law’s authority, into which historicising techniques and anti-metaphysical approaches have long been incorporated. Many influential forms of international legal thought, including legal realism, positivism, critical legal studies, and game theory, have been informed by an anti-metaphysical orientation. Far from being a revolutionary insight, the claim that historicising a text can settle its meaning is just one of many claims that are already part of the broader argumentative world of international lawyers, and no more likely than any other to resolve interpretative controversies or offer the truth of legal history.