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Part I Preliminary topics, 1 Introduction

James Crawford SC, FBA

From: Brownlie's Principles of Public International Law (9th Edition)

James Crawford

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2021. All Rights Reserved.date: 09 March 2021

History of international law — Theory of international law — International organizations — Law of the sea — Use of force, war, peace and neutrality

(p. 3) Introduction

Then felt I like some watcher in the skies

When a new planet swims into his ken …


1.  Development of the Law of Nations

The law of nations, now known as (public) international law,2 developed out of the tradition of the late medieval jus gentium.3 Through an influential series of writers—Vitoria,4 Gentili,5 Grotius,6 Pufendorf,7 Wolff,8 Vattel,9 and others—it came to be seen (p. 4) as a specialized body of legal thinking about the relations between rulers, reflective of custom and practice in such matters as treaty-making, the status of ambassadors, the use of the oceans, and the modalities of warfare. The thirteenth-century rediscovery of Roman or civil law by figures such as Thomas Aquinas10 reinforced the idea that law could structure or at least moderate the relations between kingdoms, principalities, and republics.11 The Thomist conceptualization of such relations owed much to the notion of the ‘just war’ that was later to preoccupy Grotius and others. At that time, international law—if the term was even applicable—was essentially a moral question (resulting in the elevation of the ‘just war’ to a matter of Christian doctrine); but it was engaged with issues familiar to a modern practitioner or scholar, such as territorial claims, treaties, the right of legation, and maritime transit. A signal development hinting at advances yet to come was that war was seen as the prerogative of the sovereign:

For it is not the business of a private individual to declare war, because he can seek for redress of his rights from the tribunal of his superior. Moreover it is not the business of a private individual to summon together the people, which has to be done in wartime. And as the care of the common weal is committed to those who are in authority, it is their business to watch over the common weal of the city, kingdom or province subject to them.12

The Treaties of Westphalia of 1648–9—ending the Thirty Years War—are often regarded as at the origin of what we now call international law, hence the standard reference to the public order system founded on state sovereignty as ‘Westphalian’. But this is anachronistic: while the Treaties may have consolidated the idea of the nation state they neither created nor constituted the law of nations, nor did they establish (outside Germany) any new political or legal institutions.13

In terms of intellectual history, international law was European in origin, although the Europe in question was large, extending to the whole Mediterranean, to Russia and the Near East; thence international law travelled with the colonizers to the Americas, to Asia, to Africa, and eventually to Oceania.14 At this time, Europe was not chauvinistic in defining membership of the international system.15 For example, the Ottoman Empire was accepted as a valid participant as early as 1649.16

(p. 5) In Asia, a number of states such as Siam/Thailand, China, and Japan survived the colonial onslaught and continued to assert their independence, as demonstrated by Macartney’s embassy to China in 1792 and his acid reception by the Qianlong Emperor.17 By the mid-nineteenth century, China had been largely cowed by the use of gunboat diplomacy, leading to the Treaties of Beijing in 1860.18 Japan, by contrast, engaged in a controlled opening to the west, with British naval advisers and an early translation of Wheaton’s International Law.19 A few Asian nations were able to remain independent, either because it was convenient for the colonial powers (as in the case of Siam/Thailand) or because the state succeeded in internal modernizing (as in the case of Japan, whose navy crushed Russia’s at the battle of Tsushima in 1905). Similarly, Ethiopia was able to maintain its independence at the expense of Italy following the latter’s defeat at the battle of Adowa in 1896. The remainder of the African continent, however, was subjugated: following the Berlin Conference of 1884 and the ‘Scramble for Africa’,20 it was divided between Great Britain, France, Belgium, Germany, Spain, Portugal, and Italy to create a political landscape that would last until after the Second World War.21

By this stage, the ‘modern structure’ of the law of nations was recognizably in place. The system of diplomatic relations, recognition, international organizations, treaties, and customary international law had taken on essentially modern contours. At the same time, colonialism had reshaped the world in a Eurocentric image. By the 1920s, the number of states in the world had been reduced to some 64, of which 16 were former Spanish and Portuguese colonies in South and Central America. Of the non-European nations, only seven—Ethiopia, Liberia, the Ottoman Empire (Turkey), Thailand, China, Japan, and Afghanistan—had managed to retain a measure of independence.

At the same time, sovereignty was assigned unique value in the international sphere. By the 1920s, international law was seen as entirely dependent on the consent—express or implied—of states,22 and as applicable to states alone: ‘Since the Law of Nations is based on the common consent of individual States, and not of individual human beings, States solely and exclusively are the subjects of International Law.’23 But the influence of earlier eras was not entirely expunged. Even at this point in time—the crest of (p. 6) the positivist wave—the Permanent Court of International Justice had indicated that rights under international law could be conferred on individuals.24

At around this time, international legal personality gained an added dimension with the emergence of international organizations. In the nineteenth century, states moved from the bilateral treaty and reliance on diplomatic contact to other forms of cooperation. The Congress of Vienna (1814–15) heralded an era of international conferences and multilateral treaties: later there appeared river commissions such as the European Commission of the Danube (1856) and administrative unions such as the International Telegraph Union (1865). The Hague Peace Conferences of 1899 and 1907 failed to prevent a world war, but initiated a tradition of multilateral regulation of armed conflict and the idea of a permanent court. After 1919 the League of Nations and after 1945 the United Nations instituted more developed attempts at peacekeeping arrangements, and many specialized institutions concerned with technical, economic, and social cooperation were established. Permanent organizations with executive and administrative organs paralleled but did not replace the system of ad hoc diplomacy and conferences.25

Over the course of the twentieth century, international law underwent a profound process of expansion. Developments included, inter alia, the creation of international organizations of universal membership with treaty-making powers (see chapter 7); detailed elaboration of the law of the sea (see chapters 1113); the establishment of permanent bodies (or at least permanently available institutions) for the settlement of international disputes, including ‘mixed’ disputes between states and private parties (see chapter 32); the prohibition on the use of force by states (see chapter 33); the emergence of various sub-disciplines or specialist areas of work and study, notably, human rights (see chapter 29), international environmental law (see chapters 14, 15), international economic law,26 international criminal law (see chapter 30), and progress towards the codification of international law, principally through the work of the International Law Commission.27

2.  International Law as Law

At an elementary level, the system of international law is derived from four sources, enumerated in Article 38(1) of the Statute of the International Court of Justice: (1) treaties; (2) customary international law; (3) general principles of law; and (4) ‘judicial decisions and the teachings of the most highly qualified publicists of the various (p. 7) nations, as a subsidiary means for the determination of rules of law’.28 But these, important in their own right, tell us little about the wider intellectual history of the field or its normative underpinnings.

(A)  Natural law origins

The early development of international law saw its gradual separation from natural law, a process spurred on by the Reformation and the wars of religion, notably the Thirty Years War which ended with the Peace of Westphalia (1648). Natural law as a school of thought had emerged from the philosophical traditions of Roman law and the Roman Church, which conceived of a universal jus naturale (natural law properly speaking) of which the jus gentium (the law of peoples) was a subset.29 Natural law, thus conceived, was universal; this was the background from which emerged Vitoria, Grotius, and other early theorists. Their contribution, wittingly or not, was the separation of the jus gentium from the jus naturale and its modulation into a law of nations, which applied specifically to the rulers of states. This was particularly evident in the work of Grotius, who depicted international law as the gradual development of universal principles of justice which could be deciphered through human agency (independent of received religion):

But as the Laws of each State respect the Benefit of that State; so amongst all or most States there might be, and in Fact there are, some Laws agreed on by common Consent, which respect the Advantage not of one Body in particular, but of all in general. And this is what is called the Law of Nations, when used in Distinction to the Law of Nature ….

Let it be granted then, that Laws must be silent in the midst of Arms, provided they are only those Laws that are Civil and Judicial, and proper for Times of Peace; but not those that are of perpetual Obligation, and are equally suited to all Times. For it was very well said … That between Enemies, Written, that is, Civil Laws, are of no Force, but Unwritten are, that is, those which Nature dictates, or the Consent of Nations has instituted …. [T]here are some Things, which it would be unlawful to practise even against an Enemy.30

Thus understood, the law of nations was a system of norms, whether derived from a universally applicable ‘natural’ morality or attested by ‘the Consent of Nations’. But over time thinking on the subject became progressively more concerned with a limited agenda of legal issues external to the state, as can be seen from a side-by-side comparison of Grotius’s De iure belli ac pacis (1625) and Vattel’s Le Droit des gens (1758). The bridge between the two was Wolff, who attempted a description of the jus gentium according to scientific principles.31 Wolff argued that collective society could not be (p. 8) promoted unless states formed a universal political entity, a ‘supreme state’ from which would proceed the law of nations:32

[A]ll the nations scattered throughout the whole world cannot assemble together, as is self-evident, that must be taken to be the will of all nations which they are bound to agree upon, if following the leadership of nature they use right reason. Hence it is plain, because it has to be admitted, that what has been approved by the more civilized nations is the law of nations.33

Wolff was the progenitor of Vattel’s Le Droit des gens, which could claim to be the first international law textbook.34 But Vattel’s text was at odds with many of Wolff’s conclusions, most notably with the concept of the ‘supreme state’, preferring instead to see the (European) state system as a collective capable of acting in the common interest.35 Thus Vattel asserted that the continent formed …

a political system in which the Nations inhabiting this part of the world are bound by their relations and various interests into a single body. It is no longer, as in former times, a confused heap of detached parts, each of which had little concern for the lot of the others, and rarely troubled itself over which did not immediately affect it. The constant attention of sovereigns to all that goes on, the custom of resident ministers, the continual negotiations that take place, make of modern Europe a sort of Republic, whose members—each independent but all bound together by a common interest—unite for the maintenance of order and the preservation of liberty. Hence arose that famous scheme of the political balance, or the equilibrium of power.36

Subsequently, no less a figure than Kant (1724–1809)37 sought to recharacterize the binding character of international law, proposing an international federation of republican states (foedus pacificum)—along substantially similar lines to Wolff’s ‘supreme state’38—backed by coercive rules, as the only method by which a secure and lasting peace could be achieved:

There is only one rational way in which states coexisting with other states can emerge from the lawless condition of pure warfare. Just like individual men, they must renounce their savage and lawless freedom, adapt themselves to public coercive laws, and thus form an international state (civitas gentium), which would necessarily continue to grow until it embraced all the peoples of the earth. But since this is not the will of the (p. 9) nations, according to their present conception of international right … the positive idea of a world republic cannot be realised. If all is not to be lost, this can at best find a negative substitute in the shape of an enduring and gradually expanding federation likely to prevent war. The latter may check the current of man’s inclination to defy the law and antagonise his fellows, although there will always be a risk of it bursting forth anew.39

(B)  From positivism to the present day

The early modern period also saw the emergence of ‘sovereign’ states from the claims of Empire, secular or religious. States emerged as material, independent entities and international law was one of the ways they developed of managing their relations. The apparent paradox of how law can operate between sovereigns is resolved by the priority given to consent in the formation of legal obligation and by the imperative need for cooperation in interstate affairs—combined with the insight that sovereignty includes the capacity to make permanent commitments, treaties and not merely truces.40 Indeed, the law itself begins to say what it takes to become a state and what, as a matter of law, it means to be a state.

The law of nations developed within a system wholly lacking in other institutions, and international law remains highly state-centric, a position reinforced from the early nineteenth century by the development and subsequent dominance of positivism as an account of law and legal obligation. Positivism was distinguished by the notion that only positive law—that is, law which had in some form been made by authority—could be considered true law. International law, which could only with difficulty be seen to be made—and then in a diffuse way—was caught up in this.

Positivism sees law as an emanation of power, the command of a sovereign enforced by a sanction. International law—not law above the state but law between states, enforceable, short of war, by way of moral opprobrium or by denial of benefits—is difficult to account for on such a basis. Indeed, according to some positivists, notably John Austin (1790–1859), international law was only ‘law improperly so called’.41 In this sense, Austin conjectured:

[T]he law obtaining between nations is not positive law: for every positive law is set by a given sovereign to a person or persons in a state of subjugation to its author … [T]he law obtaining between nations is law (improperly so called) set by general opinion. The duties which it imposes are enforced by moral sanctions: by fear on the part of nations, or by fear on the part of sovereigns, of provoking general hostility, and incurring its probable evils, in case they shall violate maxims generally received and objected.42

(p. 10) According to Austin, international law did not comply with the positivist axiom: in the international system there was by definition no single sovereign, thus no command, and sanctions were decentralized and sporadic. His was an extreme position, not inherent in positivism as such but in the dogma of a single sovereign as the fount of all law. Austin’s friend and intellectual predecessor—Jeremy Bentham (1748–1832)—had no such issue with international law, principally because he thought that national sovereigns, just as they could proclaim laws for the benefit of their own communities, could together promulgate international law: they were not disabled from collective action.43 Bentham, unlike Austin, also believed that a real law could be enforced by a religious or moral sanction:

When a foreign state stands engaged by an express covenant to take such a part in the enforcement of such a law as that in question, this is one of the cases in which a foreign state is said to stand with reference to such law in the capacity of a guarantee. Of a covenant of this sort many examples are to be met with in the history of international jurisprudence.44

A more refined version of positivist legal theory was elaborated by HLA Hart (1907–92). Drawing on Kelsen, Hart distinguished three categories of rules: (1) primary rules, concerning human action and interaction; (2) secondary rules (rules of adjudication, enforcement, and change) which underpin and operate in relation to the primary rules; and (3) the master ‘rule of recognition’, which enables the observer to identify the components of the system and to treat them as legal. It was the internal attitude, mainly of the officials, those responsible for the application of the secondary rules, which marked the system as legal and not merely a set of social rules. What mattered was not their acceptance of primary rules but their acceptance of the system by which those rules were generated and applied: the combination of primary and secondary rules was perceived as the essence of law.45

Measured by this more complex standard, Hart saw international law as a marginal form, possessing some but not all the characteristics of a developed legal system and then only imperfectly.46 It had only rudimentary institutions of adjudication, enforcement, and change—no courts of compulsory jurisdiction, no legislature, a frail internal attitude on the part of officials: ‘no other social rules are so close to municipal law as international law’,47 but social rules they remained.

This position was the subject of critical scrutiny by Brownlie, who argued that whatever the theoretical overlay of law/not law imposed by Hart (and positivists in general), the reality of international law told a different story:

The lack of compulsory jurisdiction and a legislature is regarded by Hart not as the special feature of a system which operates in conditions of a certain kind, but as the marks of (p. 11) an outcast, of a butterfly which is not wanted for a pre-determined collection. Yet … the stability of international relations compares quite well with internal law, given the grand total of municipal systems ruptured by civil strife since 1945. And whilst it may be said that international law lacks secondary rules, this matters less if one accepts the view that secondary rules do not play such a decisive role in maintaining the more basic forms of legality in municipal systems.48

(C)  The basis of obligation

In fact, there are many examples of public order systems which lack an identifiable sovereign but manage to function—ranging from the customary laws of indigenous societies to the law of the European Union. The classification of a system as legal does not predetermine its effectiveness: witness various national law systems in greater or lesser disarray. The question is whether the rules, traditions, and institutions of a given system enjoy at least some salience within the relevant society, meet its social needs, and are applied through techniques and methods recognizably legal—as distinct from mere manifestations of unregulated force. There is no reason to deny to such systems the classification of being legal—recognizing, however, that this leaves many questions open.

During the twentieth century, this understanding of international law has been further articulated through sociological theories,49 as well as, latterly, by the resurgence of a more rigorous and pragmatic natural law approach.50 In particular, John Finnis has defended the idea of an international law—particularly customary international law—able to emerge without being made by anyone with authority to make it, and without the benefit of Hart’s secondary rules for the authorized generation and alteration of rules:

[A]lthough there are direct ‘moral’ arguments of justice for recognizing customs as authoritative … the general authoritativeness of custom depends upon the fact that custom-formation has been adopted by the international community as an appropriate method of rule creation. For, given this fact, recognition of the authoritativeness of particular customs affords all states an opportunity of furthering the common good of the international community by solving interaction and co-ordination problems otherwise insoluble. And this opportunity is the root of all legal authority, whether it be the authority of rulers or (as here) of rules.51

(p. 12) 3.  The Reality and Trajectory of International Law

(A)  The state and sovereignty

States are ‘political entities equal in law, similar in form … the direct subjects of international law’.52 Despite the manifest historical contingencies involved, once statehood is generally recognized, a new situation arises: the new state is ‘sovereign’, has ‘sovereignty’;53 and this is true no matter how fragile its condition or diminutive its resources. In this respect, sovereignty has not evolved much from the position described by Vattel in the eighteenth century:

Since men are naturally equal, and a perfect equality prevails in their rights and obligations … nations composed of men and considered as so many free persons living together in a state of nature, are naturally equal, and inherit from nature the same obligations and rights. Power or weakness does not in this respect produce any difference. A dwarf is as much a man as a giant; a small republic is no less a sovereign state than the most powerful kingdom.54

The state monopoly of sovereignty—and the capacity to act on the international plane that it entails—has been the subject of much criticism, to the point that it is suggested that the word be avoided entirely.55 A stronger challenge is the opposition to sovereignty as the key organizing concept of the international community. With the emergence of privatization and globalization as influential forces within the world economy, it is argued, sovereignty bears less resemblance to the way things are, a perception heightened when viewed against a background of anti-formalism and rule scepticism: from that perspective, sovereign equality, a formal idea if ever there was one, is an obvious target.

These criticisms call for a response. For example, Kingsbury emphasizes the disadvantages of any normative transformation:

State sovereignty as a normative concept is increasingly challenged, especially by a functional view in which the state loses its normative priority and competes with supranational, private and local actors in the optimal allocation of regulatory authority. But discarding sovereignty in favour of a functional approach will intensify inequality, weakening restraints on coercive intervention, diminishing critical roles of the state as a locus of identity and an autonomous zone of politics, and redividing the world into zones.56

But it is also important to stress the flexibility of the concept of sovereignty and its capacity to provide a common denominator for the world’s varied cultures and (p. 13) traditions such that an international society is possible. As a concept, sovereignty carries limited substantive consequences and is consistent with a range of internal forms of government.57

(B)  The institutional structure

One of the major developments in the past century has been the emergence of international organizations with universal membership that seek to regulate the use of force between states.58 Two such organizations may be identified, each the product of a World War. The first, the League of Nations, largely conceived by US President Woodrow Wilson,59 was established as part of the Peace of Versailles in 1919;60 but the US did not join and it disintegrated over the course of the 1930s. The second, the United Nations, was established by the Charter of the United Nations in 1945.61 Despite many tribulations, it still occupies the field as the general-purpose forum of the international plane.

Although the two organizations are superficially similar, different strategies were adopted to regulate the interaction of states. The Covenant of the League of Nations did not outlaw war, as distinct from limiting the circumstances of resort to war (Arts XII, XIII, XV). Indeed, it sought to use the institution of war as a response to the violation of its provisions (Art XVI).

  1. 1.  Should any Member of the League resort to war in disregard of its covenants under Articles XII, XIII or XV, it shall ipso facto be deemed to have committed an act of war against all other Members of the League, which hereby undertake immediately to subject it to the severance of all trade and financial relations, the prohibition of all intercourse between their nationals and the nationals of the covenant-breaking State, and the prevention of all financial, commercial and personal intercourse between the nationals of the covenant-breaking State and the nationals of any other State, whether a Member of the League or not.

Article XVI sought to guarantee the key commitments or covenants which positioned the League as a system for collective security and guarantor of the performance of obligations under international law. A central procedural requirement was that of unanimity or qualified unanimity within the League Council, with guarantees for representation of any Member ‘during the consideration of matters specifically affecting the interests of that Member’ (Arts IV, V). In practice, the idea of ‘automaticity’ of (p. 14) sanctions was watered down—but automaticity was one of the factors which kept an isolationist US outside the League.62

The UN is a very different construct. It was created independently of any peace treaty, avoiding the unfortunate association with a punitive peace that had dogged the League. The close connection between commitment and sanction that characterized the Covenant was ruptured and replaced by a broad discretionary power vested in the Security Council. Where the Covenant overtly attempted to guarantee international law, backed by a system of collective security, the Charter outlawed the unilateral use of force outright save in defined and limited circumstances (Arts 2(4), 51). Chapter VII of the Charter gives the Security Council power to respond or not respond, limited by the deliberately vague term ‘threat to or breach of the peace or act of aggression’ (see chapter 33). Where the League required consultation and unanimity in the decision-making process, the Charter withdrew the veto from all except the five Permanent Members (Art 27(3))—the US, the UK, France, the People’s Republic of China (formerly the Republic of China), and Russia (formerly the USSR). The veto ceased to be a concomitant of sovereignty and became a guarantee that the five major powers could not be outvoted on key issues.63

In Reparation for Injuries, the International Court accorded to the UN claim-bringing capacity analogous to that of a state: the founding Members of the UN representing ‘the vast majority of the members of the international community’ had such capacity.64 Especially through the Security Council, the UN is influential in matters of security.65 There are other influential institutions, universal and regional, and bilateral diplomacy continues and may be decisive on particular issues.

(C)  A system of international laws

International law is a system of laws (albeit one that cannot be uncritically analogized to domestic legal systems).66 Moreover, it is a system which, day in and day out, is generally effective: millions of people are transported daily by air, land, and sea across state boundaries; those boundaries are determined and extended; the resources so allocated are extracted and sold; states are represented and committed. In Henkin’s words, ‘almost all nations observe almost all principles of international law and almost all of their obligations almost all of the time’.67 International law provides—in (p. 15) significant part—not merely the vocabulary of interstate relations but its underlying grammar.

[T]he reality of international law, that is to say, the actual use of rules described as rules of international law by governments, is not to be questioned. All normal governments employ experts to provide routine and other advice on matters of international law and constantly define their relations with other States in terms of international law. Governments and their officials routinely use rules which they have for a very long time called ‘the law of nations’ or ‘international law’ … The law delimits the competence of States … The law also provides tools for constructing institutions. Typically, what is, in effect, the loi cadre of the EEC is a multilateral treaty.68

In the absence of any formal hierarchy, the basis of obligation in international law is found in the practice of states, which regard certain processes, not limited to treaty-making, as generating legal rights and obligations and which normally conduct themselves with international legal rules in mind. In short, international law has the characteristics of a system, not just a random collection of rules. The basic constructs of personality, sources (including treaties), interpretation, and responsibility provide a framework within which rules may be generated, applied, and, increasingly, adjudicated upon. The system is, though, institutionally deficient. The absence of a legislature with universal authority and the consensual basis for judicial jurisdiction reinforce the voluntarist and cooperative character of most international law most of the time.

(D)  The trajectory of international law

At a fundamental level, the power structures within the international system are such that sovereignty and statehood remain the basic units of currency. Thus, states may use their power to modify the law to make rules about statehood itself—and they have done so, notably about colonial self-determination (chapter 5). They may qualify aspects of their sovereignty on an institutional basis by becoming members of international organizations (chapter 7) or accepting the jurisdiction of international tribunals (chapter 32). These developments (and others not supported by any institutional apparatus) have greatly expanded the content of international law and have diminished the sphere of domestic jurisdiction. The demands of international cooperation to give effect to the widening range of international obligations has both enhanced the rights of states and given them more obligations to fulfil. But they have not altered the character of the state nor the basis for the obligation to comply with international law.

True, the standard international legal relation is still bilateral (and this may be so even when the formal basis of the relation is found in a multilateral treaty). However, this protean version of international law is beginning to change. In part, this is because of the use of international law to create obligations in the general interest (at least of those states which accept the obligations), such as for the protection of human rights or of the environment. But there is no legal manifestation of the ‘international (p. 16) community’. Where there is an international organization, it may have rights as against state members to implement (or even to enforce) accepted standards. Where there is not, the burden falls upon states parties to take action to secure the implementation in the general interest of another state’s commitments, without themselves being direct victims of any breach of the law. It is not too much of an exaggeration to detect the development of a limited system of rules of public law in modern international law (see further, chapter 27) and, for international organizations and tribunals, a similar development of administrative law.69 There is no international criminal law which applies to states as accused, but there is an increasing body of rules, administered in part by international tribunals, which subjects the conduct of individuals (potentially including state officials) to international criminal law (see further, chapter 30).

These developments, particularly in the field of human rights, have added another category of personality (albeit heavily qualified) to those within the international legal system, namely individuals and sometimes corporations created by national law. It is no longer possible to deny that individuals may have rights and duties in international law; but what these rights and duties entail depends upon the operation of particular rules of international law and not on any inherent international personality such as that attributed to states (for human rights see further, chapter 28).

(E)  Scepticism, idealism, and reaction against international law

The fact remains that wealth and power are extremely unequally divided within and between states, and the inequalities may be growing. The absence of anything approaching an international constitution based on democratic principles allows tyrants to safely graze, sometimes for decades.70 Open breaches fester. But critics of international law have tended to approach it in extreme ways—by dismissing the project entirely,71 or by attributing to the agencies of reform almost magical powers.72 Indeed, Koskenniemi has seen the progress of international law as the function of an irresolvable duality between apology and utopia.73

More recently, a climate of scepticism and nativism can be discerned, and not only in the US. On occasions, international law is invoked, but in what seems an increasingly antagonistic way, amounting often to a dialogue of the deaf. At other times, it (p. 17) is apparently or even transparently ignored. This touches many of the arrangements governments spent the preceding period seeking to establish. Controversies over Syria, Iran, North Korea, Iraq, Libya, and Ukraine, and more generally the apparent backlash against globalization in its various forms (as seen, for example, in British withdrawal from the EU), create doubts and difficulties.74

It is easy to be sceptical of the claims of international law, given the discrepancies between the power of states, the complexity of modern military systems, and, more generally, the scope of the enterprise of international relations. It is also facile. The fact remains that there are things which manifestly need to be done which can be done only by collective action. There is no point in one state ceasing to produce chlorofluorocarbons if other states continue to do so. The gradual solution to the global problem precipitated by the hole in the ozone layer was achieved by coordinated action;75 the same may be true of climate change.76 The moratorium on the hunting of the great whales has saved some species from extinction and led to the substantial recovery of others.77 In sum, international law provides a set of techniques for addressing the collective-action problems presented by the coexistence of nearly 200 sovereign states. There is no large stock of available replacements. Despite its critics, international law provides a normative structure for a rules-based international society. At present it is being tested, possibly to destruction. But if it is destroyed we will be the worse for it.


1  ‘On First Looking into Chapman’s Homer’ (1816) reproduced in Strachan, Routledge Literary Sourcebook on the Poems of John Keats (2003) 79–82.

2  The term ‘international law’ was invented by Jeremy Bentham in 1789 and established itself in the nineteenth century in preference to the older ‘law of nations’, itself a translation of the jus gentium of Grotius and the droit des gens of Vattel: Janis (1984) 78 AJIL 405. For the history of international law: Grewe, The Epochs of International Law (1984, tr Byers 2000); Koskenniemi, The Gentle Civilizer of Nations (2002); Simpson in Crawford & Koskenniemi (eds), Cambridge Companion to International Law (2012) 25; Koskenniemi, ibid, 47; Jouannet, The Liberal–Welfarist Law of Nations (2012); Fassbender & Peters (eds), Oxford Handbook of the History of International Law (2012); Neff, Justice Among Nations (2014); Dupuy & Chetail (eds), The Roots of International Law (2014).

3  The term jus gentium originally came from Roman law, although antecedents may be identified, e.g. in the rules-based system of diplomacy of New Kingdom Egypt (1550–1069 bce) and the Bronze Age world system of the Near East: Altman, Tracing the Earliest Recorded Concepts of International Law: The Ancient Near East (2500–330 bce) (2012) ch 4. Generally: Bederman, International Law in Antiquity (2001); Bederman in Armstrong (ed), Routledge Handbook of International Law (2009) 115–25.

4  ca 1492–1546. Vitoria’s lectures at the University of Salamanca were transcribed by his students: e.g. De Indis (1532); De Iure belli Hispanorum in barbaros (1532). Further: Pagden & Lawrance (eds), Vitoria (1991); Brett in Fassbender & Peters (2012) 1086–9; Barthélemy et al, Les Fondateurs du Droit International (1904, repr 2014) 39–60.

5  1550–1608. De Legationibus Libri Tres (1585); Hispanicae advocationis libri duo (1613). Further: Kingsbury (1998) 92 AJIL 713; (2008) 79 BY 1; Scattola in Fassbender & Peters (2012) 1092–7; Vadi (2014) 40 NCJILCR 135; Barthélemy et al (2014) 61–95.

6  1563–1645. Mare Liberum (1609); De iure belli ac pacis (1625). Generally: Tuck, The Rights of War and Peace (1999) ch 3; Haggenmacher in Fassbender & Peters (2012) 1098–100; Barthélemy et al (2014) 119–203; May & McGill (eds), Grotius and Law (2014); van Ittersum in Orford & Hoffmann (eds), The Oxford Handbook of the Theory of International Law (2016) 82–100.

7  1632–1694. De iure naturae et gentium (1672). Further: Tuck (1999) ch 5; Haakonssen in Fassbender & Peters (2012) 1102–5; Barthélemy et al (2014) 245–79.

8  1679–1754. Ius naturae methodo scientifica pertractatum (1740–1748); Ius gentium methodo scientifica pertractatum (1750). Further: Haakonssen in Fassbender & Peters (2012) 1106; Barthélemy et al (2014) 317–36.

9  1714–1767. Le Droit des gens (1758). Further: Tuck (1999) ch 6; Chetail & Haggenmacher (eds), Vattel’s International Law in a XXIst Century Perspective (2011); Jouannet in Fassbender & Peters (2012) 1118; Barthélemy et al (2014) 337–408; Tourme-Jouannet in Orford & Hoffmann (2016) 101.

10  1225–1274. Principally: Summa Theologia (1274) and the Summa contra Gentiles (c1264–1274). Further: Budziszewski, Commentary on Thomas Aquinas’s Treatise on Law (2014).

11  Further: Kingsbury & Straumann in Besson & Tasioulas (eds), The Philosophy of International Law (2010) 33; Lesaffer in Orford & Hoffmann (2016) 38.

12  Aquinas, Summa Theologia (1274, tr English Dominican Province 1974) Question 4, Art 1.

13  Peace of Münster, 30 January 1648, 1 CTS 1; Treaty of Osnabruck, 14 (24) October 1648, 1 CTS 119; Treaty of Münster, 12 (24) October 1648, 1 CTS 271. On the Peace of Westphalia, see Osiander, The States System of Europe, 1640–1990 (1994) 16–89; Lesaffer (ed), Peace Treaties and International Law in European History (2004).

14  Generally: Anghie, Imperialism, Sovereignty and the Making of International Law (2005); Gathii (2007) 54 BLR 1013; Onuma, International Law in a Trans-civilizational World (2017).

15  Brownlie in Bull & Watson (eds), The Expansion of International Society (1984) 357.

16  E.g. Instrument for the Prolongation of the Peace between the Emperor of the Holy Roman Empire and the Sultan of Turkey, 1 July 1649, 1 CTS 457. The idea that the Ottoman Empire was only accepted into international society with the Treaty of Paris, 30 March 1856, 114 CTS 409 is a solecism.

17  Generally: Peyrefitte, The Collision of Two Civilizations (1993); Ruskola in Orford & Hoffmann (2016) 138. The Qianlong Emperor wrote to King George III explaining in greater detail the reasoning behind his rejection of the English request for a permanent embassy. He threatened that any attempt by English merchants to exceed the minimal freedoms already granted would be met with instant expulsion and ended by commanding the king to ‘[t]remblingly obey and show no negligence’.

18  24 October 1860, 123 CTS 71 (China–Great Britain); 25 October 1860, 123 CTS 79 (China–France); 14 November 1860, 123 CTS 125 (China–Russia).

19  Generally: Akashi in Fassbender & Peters (2012) 724.

20  Chamberlain, The Scramble for Africa (3rd edn, 2013). The conference was capped by the General Act concerning the Congo, 26 February 1885, 165 CTS 485, which in effect formalized the terms of the Scramble. Also: chapter 9.

21  Liberia, a free settlement of former slaves, was never colonized. Morocco was divided into Spanish and French zones but maintained a certain identity: Nationality Decrees Issued in Tunis and Morocco (1923) PCIJ Ser B No 4; Rights of Nationals of the United States of America in Morocco (France v US), ICJ Reports 1952 p 176.

22  SS Lotus (1927) PCIJ Ser A No 10, 18.

23  1 Oppenheim (1st edn, 1904) 18. Further: chapter 4.

24  Polish Postal Service in Danzig (1925) PCIJ Ser B No 11, 32–41. Also: Steiner and Gross v Polish State (1928) 4 ILR 291; Parlett, The Individual in the International Legal System (2011) ch 2.

25  On the history of international organizations: Reinalda, Routledge History of International Organizations (2009); Klabbers, Introduction to International Institutional Law (3rd edn, 2015) ch 2.

26  For public regulation of monetary, trade, and economic issues: Ruiz-Fabri in Crawford & Koskenniemi (2012) 352; Kurtz, The WTO and International Investment Law (2016). For protection of foreign investment: chapter 28.

27  For the ILC’s work: Watts, Pronto, & Wood, The International Law Commission, 1949–1998 and 1999–2009 (4 vols, 1999, 2010). Further: Bordin (2014) 63 ICLQ 535.

28  Further: Pellet in Zimmermann, Tomuschat, & Oellers-Frahm (eds), The Statute of the International Court of Justice (2nd edn, 2012) 731. On the sources of international law: chapter 2.

29  Further: Gierke, Political Theories of the Middle Age (1900, tr Maitland 1938) 73, 167, 172. Also: Lesaffer in Orford & Hoffmann (2016) 38, 44–5.

30  Grotius, De iure belli ac pacis (1625, ed Tuck 2005) I. Prelim, §§XVIII, XXVII.

31  During the 1740s, Wolff published a vast work attempting to describe natural law according to science. The last volume applied these principles to the law of nations: Wolff, Ius Gentium Methodo Scientifica Pertractatum (1749, tr Drake & Hemelt 1934).

32  Tuck (1999) 187–8.

33  Wolff (1749, tr Drake & Hemelt 1934) §20.

34  The influence of Vattel was perhaps strongest in the newly formed United States of America. Generally: Janis, The American Tradition of International Law (2004); Oosterveld, The Law of Nations in Early American Foreign Policy (2016) 26–7.

35  Tuck (1999) 191–2; Gordley, The Jurists (2013) 191–2. Also: Allott, The Health of Nations (2002) 412–16, lamenting Vattel’s victory over Wolff.

36  Vattel, Le Droit des gens (1758) III.iii.§47.

37  On Kant and international law: Tuck (1999) ch 7; Perreau-Saussine in Besson & Tasioulas (2010) 53; Werner & Gordon in Orford & Hoffmann (2016) 505–25. For Kant’s own work, see the polemic ‘Perpetual Peace: A Philosophical Sketch’ (1795) reproduced in Reiss (ed), Kant: Political Writings (2nd edn, 1992) 93.

38  Perreau-Saussine in Besson & Tasioulas (2010) 53, 59 n33; Neff, Justice Among Nations (2014) 188–9; cf Tuck (1999) 219–20.

39  Kant (1795) 105.

40  SS Wimbledon (1923) PCIJ Ser A No 1, 25.

41  Austin, The Province of Jurisprudence Determined (1832, 1995 edn) 123.

42  Ibid, 171.

43  For an analysis of Bentham in this respect: Janis (1984) 78 AJIL 405, 410–15.

44  Bentham, An Introduction to the Principles of Morals and Legislation (1789, 1970 edn) 68–70.

45  Hart, The Concept of Law (2nd edn, 1994) ch 5.

46  Ibid, ch 10.

47  Ibid, 237.

48  Brownlie (1981) 52 BY 1, 8.

49  Notably through the work of Myers McDougal and the ‘Yale’ or ‘New Haven’ school of international legal thinking: e.g. McDougal (ed), Studies in World Public Order (1987); McDougal & Feliciano, The International Law of War (1994). Further: Reisman (1992) 86 PAS 118; Reisman, L’École de New Haven de Droit International (2010).

50  Orakhelashvili, ‘Natural Law and Justice’ (2007) MPEPIL; Gordon in Orford & Hoffmann (2016) 279.

51  Finnis, Natural Law and Natural Rights (2nd edn, 2011) 244 (emphasis added); the whole passage (ibid, 238–45) should be read.

52  Reparation for Injuries suffered in the Service of the United Nations, ICJ Reports 1949 p 174, 177–8.

53  Generally: Crawford in Crawford & Koskenniemi (2012) 117; Chinkin & Baetens (eds), Sovereignty, Statehood and State Responsibility (2015).

54  Vattel, Le Droit des gens (1758) I, Prelim, §18.

55  ‘[T]he sovereignty of states in international relations is essentially a mistake, an illegitimate offspring’: Henkin (1999) 68 Fordham LR 1, 2.

56  Kingsbury (1998) 9 EJIL 599, 599.

57  Skinner in Kalmo & Skinner (eds), Sovereignty in Fragments (2010) 26, 46.

58  Further: Sheeran in Weller (ed), The Oxford Handbook of the Use of Force in International Law (2015) 347. On the history of international organizations: Claude, Swords into Plowshares (4th edn, 1971); Reinalda (2009); Klabbers (3rd edn, 2015) ch 2.

59  Schwietzke, ‘Fourteen Points of Wilson (1918)’ (2007) MPEPIL.

60  Covenant of the League of Nations, 28 June 1919, 225 CTS 195. See Fleury in Boemeke, Feldman, & Glaser (eds), The Treaty of Versailles (1998) 507; Graebner & Bennett (eds), The Versailles Treaty and its Legacy (2011).

61  26 June 1945, 892 UNTS 119.

62  E.g. Walters, 1 History of the League of Nations (1952) 66–74.

63  On proposals for the reform of the Security Council: Bourantonis, The History and Politics of UN Security Council Reform (2005); Szewczyk (2012) 53 Harv ILJ 449; Schwartzberg in Finizio & Gallo (eds), Democracy at the United Nations (2013) 231.

64  ICJ Reports 1949 p 174, 185.

65  Further: Lavalle (2004) 41 NILR 411; Talmon (2005) 99 AJIL 175; Bianchi (2006) 17 EJIL 881; Joyner (2007) 20 LJIL 489; Orakhelashvili, Collective Security (2011) 220–2; Popovski & Fraser (eds), The Security Council as Global Legislator (2014); Deplano, The Strategic Use of International Law by the United Nations Security Council (2015).

66  The value of municipal law analogies was proclaimed (to the point of overstatement) by Hersch Lauterpacht (1897–1960): Lauterpacht, Private Law Sources and Analogies of International Law (1927); Lauterpacht, Function of Law (1933, repr 2011) ch 6.

67  Henkin, How Nations Behave (2nd edn, 1979) 47; cf Koh (1997) 106 Yale LJ 2599.

68  Brownlie (1981) 52 BY 1, 1–2.

69  On the emergence of a ‘global administrative law’: Elias, The Development and Effectiveness of International Administrative Law (2012); Cassese, Research Handbook on Global Administrative Law (2016).

70  Brownlie (1981) 52 BY 1, 2 (admitting that at any one time ‘international society contains a certain number of dangerous eccentrics’).

71  Notably within the US academy: e.g. Goldsmith & Posner, The Limits of International Law (2005). Also: Bradley, International Law in the US Legal System (2nd edn, 2015); Roberts, Is International Law International? (2017).

72  E.g. Pogge in Crawford & Koskenniemi (2012) 373. For a more hesitant ‘utopian’ view: Allott, The Health of Nations (2002).

73  Koskenniemi, From Apology to Utopia (2nd edn, 2005) 17; and see Werner & de Hoon (eds), The Law of International Lawyers (2017).

74  See e.g. Haas, A World in Disarray: American Foreign Policy and the Crisis of the Old Order (2017); Crawford (2018) 81 MLR 1.

75  Vienna Convention for the Protection of the Ozone Layer, 22 March 1985, 1513 UNTS 324; Montreal Protocol on Substances that Deplete the Ozone Layer, 16 September 1987, 1522 UNTS 28.

76  Carlarne, Gray, & Tarasofsky (eds), The Oxford Handbook of International Climate Change Law (2016); Bodansky & Brunnée, International Climate Change Law (2016). For international environmental law generally: chapter 15.

77  International Convention for the Regulation of Whaling, 2 December 1946, 161 UNTS 72, Art VIII and Sch I, para 10(d)–(e); Whaling in the Antarctic (Australia v Japan: New Zealand intervening), ICJ Reports 2014 p 226.