Chair in International Law, University of Edinburgh
ANTHONY PAGDEN
Distinguished Professor, University of California Los Angeles
BENJAMIN STRAUMANN
ERC Professor of History, University of Zurich
In the past few decades the understanding of the relationship between nations has undergone a radical transformation. The role of the traditional nation-state is diminishing, along with many of the traditional vocabularies which were once used to describe what has been called, ever since Jeremy Bentham coined the phrase in 1780, ‘international law’. The older boundaries between states are growing ever more fluid, new conceptions and new languages have emerged which are slowly coming to replace the image of a world of sovereign independent nation states which has dominated the study of international relations since the early 19th century. This redefinition of the international arena demands a new understanding of classical and contemporary questions in international and legal theory. It is the editors’ conviction that the best way to achieve this is by bridging the traditional divide between international legal theory, intellectual history, and legal and political history. The aim of the series, therefore, is to provide a forum for historical studies, from classical antiquity to the 21st century, that are theoretically informed and for philosophical work that is historically conscious, in the hope that a new vision of the rapidly evolving international world, its past and its possible future, may emerge.
PREVIOUSLY PUBLISHED IN THIS SERIES
The Right of Sovereignty
Jean Bodin on the Sovereign State and the Law of Nations
Daniel Lee
Jews, Sovereignty, and International Law Ideology and Ambivalence in Early Israeli Legal Diplomacy
Rotem Giladi
The
Invention of Custom Natural Law and the Law of Nations, ca.1550–1750
FRANCESCA IURLARO
3
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Series Editors’ Preface
The Law of Nations – the ius gentium – had originally been merely the law which the Romans had applied to their – predominantly commercial – relations with nonRomans. It took on a wholly new significance, however, after the ‘discovery’ of the Americas, which had in effect brought into existence what the German jurist Carl Schmitt in 1951 described as ‘the traditional Eurocentric order of international law’. In this book Francesca Iurlaro offers a broad-ranging and powerfully compelling new account of just how this new ‘order of international law’ transformed what had once been a form of law based upon a voluntary agreement between peoples, into one which was supposed to be binding on all peoples across the globe – and might thus be imposed by one people upon another. She charts the evolving strategies by which a succession of jurists, theologians, and humanists from Francisco de Vitoria in the 16th century until Emer de Vattel in the eighteenth, sought to create a ‘new law which was universally applicable to the global community (orbis), regardless of the specific cultural and historical contexts of local political communities’. This tied the Law of Nations to the Law of Nature (the ius naturae) – the Thomist and neo-Thomist elaboration of the claim that there existed in nature itself a single basic form of knowledge for all humankind, which was discoverable through the use of human reason. The Law of Nature, however, was in effect a piece of cognitive machinery capable only of generating a universal order of justice. The jurists who contributed to the creation of Schmitt’s ‘traditional Eurocentric order of international law’ required something more precise – and ultimately enforceable – something capable, in effect, of creating a true positive law. To do this they turned to custom to provide the normative foundation for a universal legal code. In so doing, however, they transformed what was understood to be ‘custom’ from a collection of exemplary regulations – which inevitably varied greatly from one people to another – into ‘an unwritten norm that the jurist could unravel from the diverse manifestations of human history.’ Out of this emerged a new genre: the ‘Law of Nature and Nations’ which dominated the thinking about the relationship between peoples and states from the mid sixteenth until the end of the eighteenth centuries. Custom was now cast, not as the accumulated practices of individual societies but as the collective expression of the consensus of all peoples (consensus omnium gentium). It was, as Francesca Iurlaro explains, interpreted ‘as being both temporally situated – an institution whose foundations resided in Roman law, Christian religion [and] European classical antiquity – and universal at the same time.’ Although there were recognized to exist customs that were restricted to individual communities, and which were, where possible, accepted as valid by the
European colonizing powers, the kind of custom capable of sustaining an inter-national law could only, as Francesca Iurlaro explains, be arrived at through sustained inquiries into a history which was believed to provide secure evidence of universality. ‘Authors of the natural law tradition’, as she puts it, ‘invented customary rules of ius gentium precisely in an open dialogue with the past.’ The customs of the ancient – European – world, ‘constructed and fictionalized as universal’ – came to stand in for those of the orbis terrarum in its entirety. Custom, it was believed was ultimately ‘capable of transitioning the naturalness of reason into the historicity of specific political and cultural context.’
For all that the creators of the Law of Nature and Nations struggled to find in history and literature – rather than in anthropology – a universal customary law, custom remained, of course, stubbornly specific to individual societies, and even if a ‘consensus of all peoples’ were to exist it would, as the 16th-century Saxon jurist Samuel Pufendorf complained, be impossible to find just what it was. Universal consensus could only, that is, ever really be a legal fiction, a counterfactual, a device as Francesca Iurlaro describes it, intended to ‘imagine concepts which are unavailable, or even impossible, in reality.’ What the Law of Nations had in fact become by the time Pufendorf was writing was not so much the assembled wisdom offered by the customary practices of the peoples of the whole world, so much as what Hugo Grotius described as the record of ‘the continual experience and testimony of the Sages of the Law’ – in other words, not so much a consensus of custom as what Francesca Iurlaro calls a ‘mere agreement among arguments’. It also, of course, meant that only those peoples who had recognized ‘sages of the law’ – and thus a recognizable legal culture – could ever plausibly be part of the “Law of Nations”. It was, as many have subsequently complained, but a short step from this to arguing that the Law of Nations was in effect only the law of ‘civilized’ nations, or as the English legal historian Robert Ward declared in 1795, that ‘what is commonly called the Law of Nations . . . is not the Law of all Nations, but only of particular classes of them; and thus there may be a different Law of Nations for different parts of the globe.’ And if that were the case, then the entire universalizing purpose of the project would seem to have collapsed altogether. As many more recent critics, in particular those from the Global South, have protested, what the Law of Nature and Nations in effect did was to divide the world not, as Ward had argued, into many, but only into two: the ‘civilized’ nations of the globe who were bound by the Law of Nature and Nations, and the non-civilized who, like pirates, would remain the ‘perpetual enemies of mankind’ – until they were gathered into the folds of the ‘civilized’.
By the time Ward was writing, however, the direction of the argument, as Francesca Iurlaro explains, had changed entirely. For the Prussian polymath Christian Wolff – known to his contemporaries as ‘our German Newton,’ – and the diplomat Emer de Vattel, the last and the most lastingly influential of the writers in the tradition of the ‘Law of Nature and Nations’, custom could no longer be
constructed, on the basis of supposedly universal history and literary tradition, by ‘the mass of jurists’ who, in Wolff’s view, only ever worked backward from ‘their preconceived opinions’. What Vattel called the ‘customary law of nations’, had, instead, if it were to possess any lasting authority, to be ‘founded on a tacit consent, or, if you please, on a tacit convention of the nations that observe it towards each other’. It had, that is, to be discoverable in some real historical past, and recognized as local positive law.
The Invention of Custom offers an historical account based both on the wider theoretical issues involved in the attempts to construct a persuasively universal ‘Law of Nature and Nations’ as well as of attempts by the very many jurists involved to apply this to specific cases of inter-state relationships from how to deal with cannibalism to such perennial questions as the rights of prisoners of war, and the status of ambassadors. In the end as Francesca Iurlaro writes: ‘Looking at the past is a value-making activity; it relies on a certain, culturally loaded, idea of temporality.’
This book offers what she describes as a ‘history of custom as an episode in the history of historiography’. But although modern international law may claim to have entirely shed its ties to the natural law tradition, and thus to any reliance upon any specific historical past, it is still the case, she argues, that it remains ‘to some extent, a means of ordering the world through histories’. Until the story she has to tell in this book has been fully understood, modern international lawyers run the risk of being condemned, in her own words, to ‘replace old fabrications of the legal imagination with new founding fathers, new fictions, and new myths.’
Anthony Pagden
Acknowledgments
It is incredibly hard to do justice to all the people and institutions that supported the publication of this book. It took way more than the proverbial village. However, I will try, while I take full responsibility for any errors or mistakes it may contain.
This book is a revised version of my PhD dissertation, which I defended in September 2018 at the European University Institute (EUI), under the supervision of professor Nehal Bhuta. Nehal Bhuta deserves a special place in this thankful note. Over the past years, he has always supported and challenged me with his brilliant mind and enthusiasm, and always encouraged me to see the theoretical forest whenever I was getting too lost in my textual trees. I am grateful that I had the chance to meet him, and to have been exposed to his intellectual generosity.
The openness of the EUI academic environment made this journey even more engaging. Thanks are due to all the people I met there, professors, fellow researchers, and friends, who have supported me over these years in various and often unconscious ways. Special thanks are due to the members of my PhD committee, Benedict Kingsbury, Martti Koskenniemi, and Ann Thomson, who offered stimulating feedback, guidance, and support to help me turn this thesis into a book for publication. To achieve this goal, I have benefited from the support of various institutions which provided me with all the time, financial support, and intellectual excitement I needed to finish it. I am grateful to Anne Peters and Armin von Bogdandy for their hospitality at the Max Planck Institute for Comparative Public Law and International Law (MPIL) in Heidelberg back in 2018, where I spent the summer as a visiting scholar; and for welcoming me again in 2020 as an Alexander von Humboldt Postdoctoral Fellow. Thanks are due to the Alexander von Humboldt Stiftung for granting me such fellowship, time, and freedom to think, and financial support to work with ease. I am immensely grateful to Benedict Kingsbury, my supervisor at New York University School of Law, where I spent the academic year 2019–20 as a Global Postdoctoral Fellow, as well as to the Hauser Global Law School Program for sponsoring the fellowship; and to Marco Geuna (Università degli Studi di Milano), with whom I had the privilege to work as a research fellow in the first months of 2019.
Thanks are also due to Daniel Allemann, Stefano Bacin, Alessandro Barchiesi, Erica Benner, Tommaso Braccini, Annabel Brett, Hans Blom, Maria Adele Carrai, Paolo Carta, Gianmario Cattaneo, Bhupinder S Chimni, Janet Coleman, Emanuele Conte, Jean D’Aspremont, Grainne de Burca, Wim Decock, Stefano di Bella, Paul J du Plessis, Vanda Fiorillo, Alberto Frigo, Marco Geuna, Frank Grunert, Pablo Kalmanovitz, Claus Kreß, Matthias Kumm, Randall Lesaffer, Karin Loevy, Ian
Maclean, Loris Marotti, Panos Merkouris, Christoph Möllers, Luigi Nuzzo, Paolo Palchetti, Pasquale Pasquino, Anne Peters, Marie Petersmann, Andrea A Robiglio, Merio Scattola, Florian Schaffenrath, Peter Schröder, Luca Scuccimarra, Luigi Silvano, Gabriella Silvestrini, Koen Stapelbroek, Benjamin Straumann, Laura Viidebaum, Armin von Bogdandy, Christopher Warren, Jan Waszink, Joseph H Weiler, Tleuzhan Zhunussova, and Simone Zurbuchen, who provided valuable comments on single chapters or on the project itself, and have all definitely helped me get this book in a better shape. My conversations with Martti Koskenniemi offered precious intellectual stimulation throughout the process of writing and thinking about history and international law; I am deeply grateful for his generosity and support. Anthony Pagden provided essential feedbacks to an early draft of my chapter on Vitoria, and to the project in general. I am grateful for his encouragement. Thanks are due to Thomas Duve, who kindly agreed to let me workshop the first part of the book at the Max Planck Institute for European Legal History in September 2020. I owe much gratitude to him and the Salamanca Team. Christiane Birr, Andreas Wagner, José Luis Egío García, Matthias Lutz-Bachmann, Manuela Bragagnolo, Stephan Vogenauer, and Alexandra Woods all helped me think through the book, and about its weaknesses and its strengths. I also would like to thank the amazing editors at OUP Law, Jack McNichols and Merel Alstein, for their valuable support during the publication process, and the anonymous reviewers for their precious comments to the book manuscript.
My fellow EUI friends Rían Derrig and Dimitri van den Meerschen, as well as Mark Somos and Edward Jones Corredera, have read various drafts and sections of this book and considerably improved its shape: a big, heartfelt thank you to all of them for their friendship and collegiality, which made me feel less isolated in this strange world named academia. My discussions with Ed were immensely inspiring and helped me look at the main narratives of this book with more clarity and boldness; his intellectual generosity and support have been essential in the last weeks prior to submission, and nurtured many of the reflections I discuss in the introduction and conclusion to this book. I am really grateful that Grotius made us colleagues. A similar huge thank you to Raphael Schäfer, Silvia Steininger, Julia Emtseva, Erin Pobjie, and Tom Sparks, for helping me feel at home in Heidelberg with the kindness of their friendship; and to all the participants of the ‘Tuesday Round’, our weekly meetings at MPIL, for providing essential feedback to the final drafts of the book.
My family has always been there for me and I cannot thank enough my father Benedetto, my mother Maria, and my sister Alessandra for their unconditional love. A big chunk of this book was revised during our first Covid lockdown together, while cooking, baking nervously, and occasionally yelling at each other. I am grateful I could spend that particularly unsettling time, and explore what it meant existentially, with all of them. Giuliano Graziani, Noemi Macerola, and Antonella Patrizi have provided essential, both personal and professional, support
in the final stages of revision of the manuscript. Grazie davvero. Claire Vergerio would deserve a whole book of thank yous, one that would stretch way beyond the scope of this one. Most of the thoughts I explore in this book were nurtured by our conversations, while skinning bellpeppers on a kitchen counter, eating burrata, dancing in the streets of Brooklyn, or recording endless voice notes for each other. Merci, my dear friend.
I am also extremely grateful to Luca Bombardieri, whose love and amazing support have accompanied me throughout the process of thinking of and writing this book. Finally, I am grateful to Alessio and Leo, two little men with blue eyes and an unquenchable thirst for pasta whom I was lucky enough to meet while I was working on this book. They taught me a thing or two about love and lightheartedness. In the perhaps futile attempt to freeze in time the memories of all the pasta dishes we had together, and to prevent these moments from vanishing completely as time goes by, I dedicate this book to them.
1.
PART I CUSTOM, CONSCIENCE, AND NATURAL LAW
1.5
1.6
2. ‘Like Beginners in Arabic’. Custom and Reason in Francisco de Vitoria’s
2.1
2.2
2.4
2.5 A custom under the law of nations: slavery in Vitoria, de Soto, and Báñez
3. Obligation through Agreement, Agreement on Obligation: Ius gentium as custom in Francisco Suárez
3.1 Conscience and habitus: custom in Suárez
3.2 Is the ‘international’ community perfect? Ius gentium as custom, and its source of obligation
3.3 The naturalism of habitus and the self-legitimizing role of the will
3.4 How to do things with custom: ius gentium and change
PART II RHETORIC AND HUMANISM: HISTORICIZING CUSTOM
4. Custom as Historiography: Alberico Gentili 77
4.1 Custom and the historical exemplarity of humanism 77
4.2 Historiographic pragmatism and ‘the others’: Alberico Gentili on custom 89
4.3 Gentili’s ius gentium: justice, empire, and humanitas 95
4.4 Gentili’s custom
5. A Literary History of Custom: Hugo Grotius
5.1 Consuetudo, mos, consensus: custom as a distinctive feature of the law of nations
5.2 Grotius, Dio Chrysostom, and the ‘invention’ of custom
5.3 The ‘poetic’ of natural custom vs the conjectural assessment of the voluntary customary law of nations: two examples from Grotius’ De iure belli ac pacis 115
PART III THE ‘BIRTH’ OF CUSTOMARY IUS GENTIUM AS AN INDEPENDENT LEGAL REGIME
6. A Turn Inward: the Europeanization of Customary ius gentium 127
6.1 Custom as a social construct: reputation, official historiography, and the birth of state practice
6.2 Custom, love, and perfection: the problem of obligation
6.3 Against stylistic dryness: how custom freed itself from antiquity 136
7. Custom in Concentric Circles: Samuel Pufendorf’s Customary ius gentium Between Glory and State Interests
7.1 Pufendorf’s main conceptual innovations
7.2 Natural law as the science of morality
7.3 Law of nations in times of peace: international agreements and reason of state
7.4 The problem of consensus: Pufendorf’s method 151
7.5 Law of nations in times of war: customary ius gentium and social reputation
8. Christian Wolff and His ius gentium consuetudinarium 162
8.1 Wolff’s philosophization of customary ius gentium
8.2 Wolff’s system: the psychological foundations of natural law 164
8.2.1 Consensus
8.2.2 Perfectio
8.2.3 Concursus
8.3 Laws of nature, natural law, and ius gentium: the perfection of civitas maxima
8.4 The parody of ius gentium consuetudinarium: between philosophy and history 175
9. Vattel’s Doctrine of the Customary Law of Nations
9.1 Vattel’s custom between sovereign interests and the principles of natural law
9.2 Vattel vs Wolff: self-interest as the foundational principle of natural law 183
9.3 Distinguished, yet not treated separately: the natural and positive law of nations 185
9.4 Customary law of nations: between facts and principles 189
9.5 Facts with meaning: customs originating in an overlapping of practice and principles 192
9.6 ‘Non-indifferent’ customs
9.7 Is the violation of custom punishable?
i. Custom after natural law? Revivals, ruptures, and reflections
ii. ‘After’ natural law?
iii. An exercise in (dis)belief: custom and historical methodology
Introduction: the ‘Problematic’ of Custom in the Natural Law and ius gentium Tradition
i. The problematic of custom
The story of the intellectual development of custom as a distinctive source of obligation among nations is as controversial as the many conflicting theories about its origins and ends.1 Custom is an inherently elusive concept. Contemporary international lawyers conceive of customary international law (CIL) as ‘evidence of a general practice accepted as law’, as stated in article 38(1)b of the ICJ Statute.2 More broadly, scholars struggle to understand where custom derives its legal force from; whether from the moral values it enshrines, and that are intentionally defended by members of a community to signal their assent to such values; or from the factual assessment of habits which acquire legal significance by mere repetition over time.
The dualism between ‘values’ and ‘facts’ is at the very core of the so called ‘twoelements’ doctrine of CIL. According to such doctrine, CIL consists both of opinio iuris (a psychological sense of legal obligation attached to a given customary norm) and state practice, i.e. evidence of its consistent observance by states. This definition of CIL conceals endless theoretical problems, to the point that some have even suggested abandoning custom as a problematic and ‘obsolete’ source of international
1 Some ‘classical’ texts facing the conceptual ambiguities of custom under international law are: Hans Kelsen, ‘Théorie du Droit international coutumier’, in Ecrits français de droit international (PUF 2001) 61–84; Anthony D’Amato, The Concept of Custom in International Law (Cornell University Press 1971); Mark E Villiger, Customary International Law and Treaties: A Study of their Interactions and Interrelations with Special Consideration of the 1969 Vienna Convention on the Law (Nijhoff 1985); Frederic Kirgis, ‘Custom on a Sliding Scale’ (1987) 81(1) American Journal of International Law 146; Martti Koskenniemi, From Apology to Utopia: the Structure of International Legal Argument (Finnish Lawyers’ Pub. Co. 1989) (hereafter Koskenniemi, From Apology to Utopia); Karol Wolfke, Custom in Present International Law (Nijhoff 1993); Michael Byers, Custom, Power and the Power of Rules (CUP 1999) (hereafter Byers, Custom, Power); Anthea Roberts, ‘Traditional and Modern Approaches to Customary International Law: a Reconciliation’ (2001) 95(4) American Journal of International Law 757.
2 Statute of the International Court of Justice, art 38.1(b). See also the recent reports on customary international law from the International Law Commission: Draft Conclusion on Identification of Customary International Law, with Commentaries (2018) A/73/10.
law.3 What comes first? Is it the psychological dimension of the acceptance of the norm, or is it a state’s effective observance of its terms? As scholars have observed, this doctrine of custom is inherently circular: to evaluate what qualifies as opinio iuris, one has to rely on some normative criterion. It is problematic, moreover, to infer such normative criterion from the mere observation of a selection of facts. And if one abstracts and generalizes conclusions about these facts in the name of a superior normative principle, then custom appears to be merely a contingent moral standard, rather than a legally binding construct.4 In spite of these provocations, contributions from scholars and jurists seeking to disentangle the conceptual difficulties of CIL are abundant in current literature.5
This is not, however, a book about overcoming the conceptual difficulties of contemporary CIL; nor is it a book on the historical genesis of the two-elements doctrine. Rather, its scope is at once more restricted, as the book focuses on the early modern natural law tradition, and more wide-ranging, to the degree that it tries to map the inherent conceptual dynamics of custom along the lines of its intellectual and historical development as an international legal source.
The concept of custom, although formulated in a different way, is already present in early modern European debates on natural law and the law of nations. However, no scholarly monograph has addressed the relationship between custom and the European natural law and ius gentium tradition. This is a book on this neglected story. It seeks to answer the question of when and how the concept of customary international law originated in European debates on natural law and ius gentium I argue that this tradition provides us with a solid conceptual framework to contextualize and understand the ‘problematic of custom’, namely, how to identify its normative content. Natural law doctrines, and the different ways in which they help construct human reason, provided custom with such normative content. By ‘normative content’ I mean a set of fundamental moral values that foundationally help identify the status of custom as either a fundamental feature or an original source of ius gentium. Thus, I ask what cultural values and practices facilitated the
3 James P Kelly, ‘The Twilight of Customary International Law’ (2000) 40(2) Virginia Journal of International Law 449; Daniel H Joyner, ‘Why I Stopped Believing in Customary International Law’ (2019) 9(1) Asian Journal of International Law 31.
4 Koskenniemi, From Apology to Utopia (n 1) 461–2.
5 Amanda Perreau-Saussine and James B Murphy (eds), The Nature of Customary Law: Legal Historical and Philosophical Perspectives (CUP 2007) (hereafter Perreau-Saussine and Murphy, The Nature of Customary Law); David J Bederman, Custom as a Source of Law (CUP 2010) (hereafter Bederman, Custom as a Source); Brian Lepard, Customary International Law: a New Theory with Practical Applications (CUP 2010); Michael Scharf, ‘Customary International Law in Fundamental Times of Change: Recognizing Grotian Moments’ (2014) 25(2) King’s Law Journal 313; Hugh WA Thirlway, The Sources of International Law (OUP 2014); James B Murphy, The Philosophy of Customary Law (OUP 2014). More recent contributions include Curtis A Bradley (ed), Custom’s Future: International Law in a Changing World (CUP 2016); Brian D Lepard (ed), Reexamining Customary International Law (CUP 2017); Monica Hakimi, ‘Making Sense of Customary International Law’ (2020) 118(8) Michigan Law Review 1487; Peter G Staubach, The Rule of Unwritten International Law: Customary Law, General Principles and World Order (Routledge 2020).
emergence of custom and rendered it into a source of the law of nations, and how they did so. In this context, as I will explain later in greater detail, mine is a story of ‘state beliefs’ rather than of ‘state practice’.6
Two crucial issues will be at the core of my analysis: first, I will qualify the nature of the interrelation between natural law and ius gentium, and explain why it matters in relation to our understanding of the idea of custom; second, I will claim that the process of its formation as a source of law calls into question the role of the authority of history. The interpretation of the past through this approach can, thus, be described as one of ‘invention’.
ii. Custom and natural law
Why natural law? What makes it so important to understand the dynamics originating what I referred to as the ‘problematic of custom’? As ever-growing literature on the history of international law suggests, the expression ius naturae et gentium refers to a non-homogeneous corpus of doctrines deriving from different intellectual lineages (juridical, theological, philosophical, literary, etc), and used to make specific transnational legal arguments. What all these doctrines have in common, however, is that they identify human reason as the ultimate source from which this ‘global’ law derives its normative power and ultimate structure – how they all differ, however, is precisely around how they conceive of human rationality. Against this background, debates on the origins of ius gentium are particularly vivid in the early modern age: does ius gentium derive from natural reason, or from free will? Does it have natural or positive origins? In commenting and reinterpreting the relevant passages of Corpus iuris civilis and Thomas Aquinas’s work, in which ius gentium is discussed, authors have developed a variety of answers to the question.7 As a result, conceptualizations of ius gentium vary extensively and often depend on the religious affiliations of their authors.8 According to an ‘essentialist’ reading, ius gentium is considered to be the same as natural law, because human nature itself exhibits an intrinsically immutable moral core, from which certain absolute legal principles can be infallibly deduced, or inferred, by observing their manifestations throughout human history. Other authors draw on a more dualistic account of ius gentium, as constituted by both positive and natural elements: natural principles
6 Koskenniemi, From Apology to Utopia (n 1) 388.
7 See Peter Haggenmacher, Grotius et la doctrine de la guerre juste (PUF 1984) (hereafter Haggenmacher, Grotius); Merio Scattola, Naturrecht vor dem Naturrecht. Zur Geschichte des Ius Naturae im 16. Jahrhundert (De Gruyter 1999) (hereafter Scattola, Naturrecht); Annabel S Brett, Changes of State: Nature and the Limits of the City in Early Modern Natural Law (Princeton University Press 2011) 37–61 (hereafter Brett, Changes of State).
8 However, Brett points out that the works of these scholars cannot be reduced to their confessional affiliation, see Brett, Changes of State (n 7) 66.
and voluntary acts play an equally crucial role in human life, but the latter are essential to the creation of agreements among sovereigns.9
According to Annabel Brett, this vast number of responses to the question of divisio iuris were attempts to grapple with, and counter, the narrative of ius gentium as ‘part of a temporal story about mankind’.10 Ius gentium was either a human institution, closely related to civil law and thus contingently dependent on sovereign wills, or a ‘detemporalized’ universal law of reason that shared a resemblance with natural law, a position commonly defended by Protestant humanists and jurists. It is useful to place the historical emergence of debates on custom in the context of ius gentium’s inherent contradiction between its atemporal universality and its temporal situatedness. In the aftermath of the European colonization of the Americas, theologians and jurists asked whether the latter could change over time – and, if so, how could it change while still being consistent with its moral content? As a matter of fact, the discussion on the customary nature of ius gentium tied in with a vivid debate concerning its derogability and its independence from natural law principles. Answering these questions was crucial to solving the problem of ‘otherness’ with which Europe was confronted in the New World. As European authors argued that American indigenous people seemed to display a lack of rationality, capacity of self-government, and, most importantly, an invincible ignorance of Christ, it was urgent to understand what kind of rules could be applied in encountering and conquering them. From this perspective, the language of natural law ideally responded, on the one hand, to the normative necessity of creating a new law which was universally applicable to the global community (orbis), regardless of the specific cultural and historical contexts of local political communities. At the same time, the discussion of what was deemed to be quintessential of human nature revealed irreconcilable cultural differences that were rather the product of history, and, ultimately, of centuries of Christian thought and practice. How was one to make sense of these differences within the linear narrative of civilization and conquest?
Custom provided the perfect conceptual tool to navigate these asymmetries: it was both closely related with natural law and its principles, and a cultural-historical product of the West. Against this background, my narrative argues that one of the first attempts to qualify ius gentium as customary emerged out of a discussion on whether it was legal to enslave prisoners of war. In Politics, Aristotle provided a justification for natural slavery based on the natural inferiority of barbarous populations – a justification that was famously used by Juan Ginés de Sepúlveda in the Valladolid debate.11 At the same time, Aristotle admitted the existence of a ‘legal’
9 Haggenmacher, Grotius (n 7) 311–59.
10 Changes of State (n 7) 77, 196, 212.
11 Juan Ginés de Sepúlveda, Demócrates Segundo (Consejo Superior de Investigaciones Científicas 1951).
type of slavery, namely that originating from the right of the winner to enslave the prisoners in a war. Relying on this basis, teologos-juristas of the School of Salamanca started qualifying the settled practice of enslaving prisoners of war as a custom under the law of nations. The legal rationale behind this custom relied on its historical (rather than natural) origin: slavery is a human institution introduced after the Fall to dispose of prisoners of war without having to kill them. This example became, thus, a topical one bearing witness to the difference between natural law and ius gentium, and of the latter’s capability of emancipating itself, within limits, from natural law. It was also a foundational one, as it provided one of the first attempts at grasping the customary nature of ius gentium, as well as its ambiguous nature as a civilizational project: as I will show, only non-Christians could be turned into slaves, while a further ‘Christian custom of freedom’ prevented Christians from enslaving prisoners of their same faith. In other words, while being in accordance with the natural principle of not killing fellow Christians, this custom was a human invention, insofar as it aimed at curbing the horrors of war, and ultimately made the institution of enslavement a profitable one. Custom’s close kinship with natural law made it natural enough to be normatively cogent; at the same time, history turned custom into a construct that could be mobilized to face the challenges of conquest, civilization, empire, and global trade.
For this reason, I argue that Brett’s ‘detemporalized’ narrative of early modern doctrines of ius gentium does not do full justice to the problematic of custom. Custom was understood as being both temporally situated – an institution whose foundations resided in Roman law, Christian religion and, as I will argue, European classical antiquity – and universal at the same time. Crucially, its temporal and spatial validity was carefully constructed and fictionalized as universal. As I will show, custom was a normative and creative project of historical invention of new rules in the mould of natural law. The bulletproof normative validity of natural law was rhetorically exploited to convey the immutability, inevitability, and moral urgency of custom.
Custom emerged as a fundamental legal category capable of transitioning the naturalness of reason into the historicity of specific political and cultural context. The emphasis on the normative aspects of custom will allow me to problematize two narratives: first, positivism, and, second, the idea of ‘state practice’, which is traditionally associated with custom. While contemporary lawyers think of positivism as opposed to natural law, I shall challenge this overly abrupt distinction and depict natural law and positive law as symbiotic forces in the creation of the language of custom. Early modern arguments on the voluntary nature of custom, far from showcasing the alleged ‘modernity’ of early modern ius gentium as an historiographic category, were rather comprised within a process that has been rightly described as one of construction of human agency.12 The study of the meaning of
12 Brett, Changes of State (n 7) 37–61.
the word ‘consensus’, and the foundational role it plays for custom, serves to illustrate this point. Far from identifying a shared agreement of political wills on a given custom (with the notable exception of Suárez), before the 17th century consensus was understood as an abstract consensus of religious and moral views. Alternatively, the concept of ‘consensus’ referred to a fictional agreement of experts and authors from the past who validated, with the authoritativeness of their testimony, the legitimacy of a given custom. Proof of customary law of nations emerged, thus, not from facts, but from arguments in favour of or against the alleged applicability of a given custom.13 As I will clarify in the next section, the place from which these arguments were drawn is history and, in particular, the European classical tradition.14
Secondly, along these lines, I will suggest that very notion of ‘state practice’ (i.e. the idea of inferring the existence of binding customary rules from generalized patterns of behaviour) was relatively undertheorized until the late 17th century. This does not imply that customary rules were not a reality of international relations from the Middle Ages onward.15 Nor do I mean to suggest that custom emerged from the void: as I will show with the custom of prisoners of war, it grew as a response to the all too real problems raised by – Mediterranean, and eventually transatlantic – trade. My argument, however, is that early modern jurists and theologians rarely turned to their contemporary practice to find sources of legitimacy of custom. On the contrary, they sought to construct its normative core by binding it tightly to natural law principles, and portraying these connections as inevitable, often challenging or condemning the legal standards of their age. Natural law, therefore, provided them with an epistemic and moral authority upon which to ground customary rules of ius gentium
Thus, this book seeks to retrace a narrative of custom as a process of historicization of natural law. To do so, I have chosen a selection of authors that have navigated the dichotomy between natural law and history, starting from debates on the legal status of the newly discovered populations in the Americas. I have then moved to how European authors of the ius gentium tradition ‘invented’ the customary law of
13 Gerald J Postema, ‘Custom, Normative Practice, and the Law’ (2012) 62 Duke Law Journal 707–38, 717, 738. Similarly, famous postcolonial international lawyer Bhupinder S. Chimni has recently vindicated the importance of deliberative reasoning (what Postema referred to as ‘custom as an argumentative practice’) for a postmodern doctrine of customary international law, which is inclusive of the perspectives of Third World States (Bhupinder S Chimni, ‘Customary International Law: a Third World Perspective’ (2018) 112(1) American Journal of International Law 1.
14 Here I take the concept of historical testimonies from the classical past in Straumann’s sense, as ‘an umbrella term . ., which would include not only accounts of historical events, but also works in the history of philosophy and law, as well as works of classical and, for Grotius, primarily Roman philosophers, lawyers, orators, and poets’. See Benjamin Straumann, Roman Law in the State of Nature: The Classical Foundations of Hugo Grotius’ Natural Law (CUP 2015) 72 (hereafter Straumann, Roman Law).
15 See Chapter 1 of this book; see Wilhelm Grewe, The Epochs of International Law (De Gruyter 2000) 89; for a more contemporary account, see Michael Jucker, Martin Kintzinger, and Rainer Christoph Schwinge (eds), Rechtsformen internationaler Politik: Theorie, Norm und Praxis vom 12. bis 18. Jahrhundert (Duncker & Humblot 2011).
nations through the language of history and myth-making, internalized its cultural values, and, eventually, abandoned such values.
iii. Custom and history
To explain the process of the invention16 of custom, I approach two dimensions that are at the intersection between history and natural law. First, to conceive of customary ius gentium as a historical artefact poses the question of what kind of universalist claim it entails, and urges us to reflect on what teleology of history it relies upon. Second, it implies a discussion of the specific politics of the histories that were used to construct legal norms for the present.17
As far as the first ‘teleological’ aspect is concerned, the question arises as to whether and to what extent we should deem custom to be an imperial project: if customary ius gentium is a product of a certain kind of history, and the specific context it applies to is Christianity, then how we approach the fabrication of such a history becomes crucial. As a matter of fact, historical pluralism and the coexistence in time of different cultural, political, and religious systems (Christian Europe on the one hand, and the indios on the other) was loaded with a teleological version of history – one where the Spanish conquistadors sought to save the indios from barbarism and, most importantly, from their ignorance of Christ. Imagining a customary ius gentium therefore required a certain degree of historical and legal abstraction. It had to be imagined from scratch beyond the practicalities of colonial governance, and often directly challenging native narratives, in order to create a Christian community of Christian values. Only then could local indigenous populations be persuaded and reoriented through religious conversion.
To conceive of ius gentium as customary calls into question the authority of history and the politics behind interpretations of the past. The interplay between the origin of custom in natural law, and the different historiographical practices that informed it, will constitute the fundamental narrative thread of this book. Building on this approach, I will argue that custom was constructed, mostly by humanist jurists, by fabricating European cultural identity through the language of classical
16 Anne Orford, ‘The Past as Law or History? The Relevance of Imperialism for Modern International Law’ (2012) 2 History and Theory of International Law Series <https://iilj.org/wp-content/uploads/ 2016/08/Orford-The-Past-as-Law-or-History-2012-1.pdf> accessed 26 July 2020 (hereafter Orford, ‘The Past as Law or History?’). D’Aspremont defines customary international law as ‘the invention of an imaginary genealogy’: see Jean D’Aspremont, International Law as Belief System (CUP 2017) 87. On the relationship between invention, tradition, and custom, see Eric Hobsbawm, ‘Introduction: Inventing Traditions’, in Eric Hobsbawm and Terence Ranger (eds), The Invention of Tradition (CUP 1983). I thank Edward Jones Corredera for directing me towards this text.
17 On natural law and historicism, see Leo Strauss, Natural Right and History: Walgreen Foundation Lectures (University of Chicago Press 1999), especially 17 on how historicism, despite its alleged lack of transcendental assumptions, implies reliance on an unspoken universal truth: that we all agree to subjugate to the authority of history.
antiquity. The story of custom was a fictional attempt to frame this identity as universal and immutable. Such fiction was then perpetuated by means of literary invention and canonization.18
Crucially, the story of ius gentium cannot be separated from the material aspects of its cultural transmission. A parallel history unfolds between the lines of the marginal notes that support the jurists’ arguments in their texts. Such a story was crafted on the shoulders of the impressive amount of scholarship that humanists were producing throughout Europe by exploring a variety of literary forms – bilingual editions of Latin and Greek classics, translations into vernacular languages, original manuscripts, commentaries, and so on.19 This scholarship created systems of authority that were used by jurists as canons of order to provide legitimation to custom; additionally, it helped them construct an ample casuistry of customary rules of ius gentium based on the values and exempla of the classical past.
iv. Ius gentium as customary vs. custom as a source of the law of nations
A note is needed on terminology. Throughout the book, I use two different operative conceptualizations of custom. Neither of them is expressly used by the authors I take under consideration, but they help us separate a two-stage process in the historical development of the concept. With the expression ‘ius gentium as customary’, I refer to the idea that ius gentium has some distinctively customary features. This means that certain customary rules of ius gentium exist, but that they do not form an independent legal regime altogether, separated from ius gentium (Parts I and II).20 Rather, whenever I conceive of custom as an autonomous legal regime that
18 However, Brett later admits her detemporalized narrative of ius gentium is paradoxical: Brett, Changes of State (n 7) 196.
19 In conceding primacy to the textual elements of transmission of ius gentium doctrines, I share the approach adopted by Straumann, Roman law (n 14); and by Christopher Warren in his Literature and the Law of Nations (OUP 2015); see also Christopher Warren, ‘History, Literature, and Authority in International Law’, in Simon Stern and others (eds), The Oxford Handbook of Law and Humanities (OUP 2020) 565. On the material aspects of transmission, see Craig Kallendorf, The Protean Virgil: Material Form and the Reception of the Classics (OUP 2015); Anthony Grafton, The Footnote: A Curious History (Harvard University Press 1997); Anthony Grafton and Lisa Jardine, From Humanism to the Humanities. Education and the Liberal Arts in Fifteenth and Sixteenth-Century Europe (Duckworth 1986); Cesare Vasoli, La dialettica e la retorica dell’umanesimo: ‘invenzione’ e ‘metodo’ nella cultura del XV e XVI secolo (Feltrinelli 1968). I refer to these texts for further bibliographical references.
20 See Chapter 1 on Arthur Schiller’s distinction between custom and customary law in Roman law. The difference between custom as a body of customary rules and customary law as an independent legal system, enforced by a specific territorial entity, relies on late 19th to early 20th century German debates on consuetudo. See Siegfried Brie, Die Lehre vom Gewohnheitsrecht. Eiene historischdogmatische Untersuchung (Minerva Verlag 1899); Rudolf Köstler, ‘Consuetudo legitime praescripta Ein Beitrag zur Lehre vom Gewohnheitsrecht und Privileg’ (1918) 39(8) Zeitschrift der Savigny-Stiftung für Rechtsgeschichte: Kanonistiche Abteilung 154; Ennio Cortese, La norma giuridica. Spunti teorici del diritto comune classico (Giuffrè 1964).
is distinguished from other sources of the law of nations (such as natural law principles, treaties, etc), I refer to ‘custom as a source of the law of nations’ (Part III). Building on this distinction, I will now briefly sketch an outline of the chapters.
Part I begins by contributing an overview of the concept of custom in the Roman and canon law tradition (Chapter 1). This will introduce the vocabulary, and some problematic aspects, of custom, that is, its inherently moral value and the controversial imperial dynamics embedded in it. While this section is far from exhaustive (an accurate analysis of the Roman and Medieval account of custom would inevitably fall out of the scope of this book), it sets the stage for the early modern reprisal of the concept. In Chapter 2, I then move on to the analysis of the different strategies that were used by theologians of the Second Scholastic (Francisco de Vitoria, Domingo de Soto, and Domingo Báñez). These influential theologians thought of ius gentium as partly made of natural law principles, partly of customs, and that it was possible to identify these through compliance with European religious beliefs. While vindicating the interdependence of custom and Christian values, they questioned to what extent ius gentium could depart from natural law without contradicting its moral tenets, and still give leeway for new practices to be established and new political necessities to be voiced.
These authors did not theorize the idea of custom as a fully independent source of the law of nations. Yet, their account was foundational because they acknowledged custom as an essential element of ius gentium, and vindicated the historical origins of specific customs. They identified the aforementioned custom concerning the enslavement of prisoners of war as a topical example of the customary origin of ius gentium. Custom responded, on the one hand, to the civilizing need to ‘habituate’ the indigenous populations to Christian morality and natural law, and to the genuine belief that everyone could change or be convinced to convert, if provided with apt means to do so. On the other hand, custom served as a jurisdictional basis for the exercise of fraternal correction through confession. This would allow indigenous people to ‘correct’ their habits, clearly perceived of as deficient and uncivilized as opposed to European standards, and to eventually join the Christian community. These peoples would then benefit from the instruments of legal protection that were granted to them by virtue of their membership.
These theologians acknowledged the historical origins of custom, but they did not substantiate it with anything more than genealogical references, while leaving open a question of political agency. The question remained: who introduced custom? Chapter 3 focuses on Francisco Suárez’s attempt at securing the moral and religious foundation of custom through his notion of ‘perfect community’, imagined as the political society of Christian sovereigns. In the fragmented space of early modern European politics, however, religious schisms within Christianity alienated European sovereigns and their interests, instead of uniting them under a common ground. Aware of the disruptive potential of religious divisions, jurists such as Alberico Gentili and Hugo Grotius took a different path to conceptualize
