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Max Planck Encyclopedia of Public International Law [MPEPIL]

History of International Law, World War I to World War II

Martti Koskenniemi

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2021. All Rights Reserved.date: 05 August 2021

World War I to World War II

Published under the auspices of the Max Planck Institute for Comparative Public Law and International Law under the direction of Professor Anne Peters (2021–) and Professor Rüdiger Wolfrum (2004–2020). 

A.  The Situation in 1919

For the contemporaries, the horrors of the Great War came as an incomprehensible shock. How could the most ‘civilized’ part of humankind engage in such destructive violence for such a meaningless cause for such a long time? Almost 1.4 million Frenchmen and 1.7 million Germans lay dead on the battlefield with the total numbers of casualties on the Allied side at five and Central Powers at three million. There was a widespread sense that something about pre-war European culture and politics had gone terribly wrong and needed to be remedied in the post-war work of reconstruction. One of the culprits of the catastrophe, it was widely assumed, had been the diplomatic system (Diplomacy). It had been based on a virtually unlimited acceptance of the search for national power and glory while its techniques for conflict-limitation—especially that of the balance of power—had shown themselves useless in checking the spiral of violence once it had begun. Nationalism, militarism, and imperialism were all indicted in the process—with both sides seeing more of these in their adversary than in themselves.

There was no return, politicians and lawyers thought, to the diplomatic system of the pre-war era. But they remained divided about the types and the extent of the needed reforms. They rejected nationalism and its formal corollary, unlimited State sovereignty, as foundations for the new system but they simultaneously declared the right of national self-determination as one of its corner-stones and instituted the operation of the organs of the League of Nations on the principle of unanimity. They rejected war as an instrument of national policy but failed to limit the means of warfare or to develop a reliable system for addressing legitimate grievances through a reliable system of peaceful change (Warfare, Methods and Means). They wanted a standing system of international organization that could prevent aggression and facilitate international co-operation for welfare and progress but also used that organization as an instrument for various national agendas and remained reluctant to provide it with sufficient resources to become an independent international player to be reckoned with.

There has never been more talk about international law and organization than in the years immediately following World War I. Significant developments were made in both thinking about international law and putting it into practice. The field became professionalized and its basic concepts and structures were set in place. It was definitely steered in an institutional direction. But progress was undermined by the contradictory aspirations of the actors and the way in which the various legal rules and institutions seemed constantly to be instrumentalized for contested purposes. Mere technical sophistication of the rules or the theories did not make their application independent of the governmental agendas. To the extent that the law sought autonomy, again, it was insufficiently equipped to become opposable to recalcitrant actors. Whether the rhetoric of legalism was sincere on all sides or not, the unstable politics made the inter-war era merely a transitional ‘twenty years’ crisis’.

Nevertheless, most of today’s basic international legal doctrines and institutions received definite shape in the 1920s and 1930s, an extraordinarily active period of legal innovation. The principles of treaty law (Treaties) and custom (Customary International Law), territorial sovereignty and legal subjects (Subjects of International Law), as well as procedural rules concerning recognition, jurisdiction of States, and the justiciability of international disputes (Judicial Settlement of International Disputes) arose not only as theoretical propositions but as aspects of the practice of international and domestic bodies. It is true that the designers of Cold War diplomacy in the 1950s concluded from the collapse of the inter-war system that legalism needed to be avoided at all costs (Cold War [1947–91]). But the power of the inter-war legal debates was attested to by the enthusiasm with which international lawyers in the 1990s and thereafter embraced such international law institutions as collective security, international criminal law, human rights and more generally, the project for the move to the rule of law in international affairs. Through these moves, post-Cold War lawyers have unearthed agendas that were at the centre of the legal developments in the early 20th century.

B.  Professionalization

Work for the integration of international law into the structures of European and American diplomacy had already commenced by the establishment of the Institut de Droit International and the International Law Association (ILA) in 1873. Nevertheless, private codification of international law never took effective root. The two institutions were soon transformed into debating societies whose members recognized each other as participants in a joint international law project but were compelled to direct their activism into the national level and the various international organizations that emerged from the Versailles Peace Treaty (1919) ((1919) 225 CTS 188). To struggle efficiently against the dangers of nationalist politics, they needed to become political themselves. In this, they were often unsuccessful.

The war had precipitated the organization of the international law profession at the national level. Several Secretaries of State had been high officials of the American Society of International Law that had already been established in 1906. In Britain, the Grotius Society was established during the war with the aim of injecting legal ideas into plans for post-war reorganization. The Deutsche Gesellschaft für Völkerrecht was set up in 1917 in co-operation between liberally minded academic lawyers and the Foreign Ministry. In Paris, an Institut—later écoledes hautes études internationales emerged at the University of Paris in 1919 to provide teaching for internationalists all over the world. Although many of these societies were in contact with each other, sometimes through the ILA, they continued to have a national profile and often supported distinctly national causes. They were instrumental in achieving the increase of international law teaching at universities and in developing a sense that international law was a profession like civil or criminal law and not just an exotic variety of philosophical contemplation. The war had interrupted plans to establish a truly international school for diplomats and international lawyers. In 1922, the Hague Academy of International Law opened its doors to a genuinely international audience.

Most foreign ministries established a special legal advisers’ office to deal with treaty matters, international institutions, and consular law (Legal Advisers). The lawyers were recruited sometimes from the diplomatic service, often from universities or private practice. With the expansion of permanent diplomacy, and the key role international lawyers played in the League of Nations, both in the Secretariat and in the delegations of Member States to League meetings, a truly international legal profession emerged that may have received its training at the national level but that was by ideology and inclination quite homogeneously internationalist.

At universities, international law was being integrated as a regular subject of the law school curriculum. But the system of teaching differed from country to country. In Germany, for example, international law was part of public law in a way that produced a distinctly constitutional perspective on it. In Italy, it was combined with private international law, thus supporting a consistently cosmopolitan outlook on both. In some countries such as France, international law remained closely linked with diplomatic history and natural law philosophy (Natural Law and Justice), while in Britain, it was taught as a mixture of commentary on cases and political situations over which continental émigrés such as Lassa Oppenheim and Hersch Lauterpacht provided a doctrinal structure. Everywhere, the complaint was continuously voiced that there was too little teaching in the discipline, especially in view of the needs of international organization.

C.  Developments in Doctrine: Dealing with Sovereignty

No theme united international lawyers in the 1920s and 1930s more than their critique of pre-war diplomacy and the balance of power that were held responsible for the slide into full-scale war in August 1914. The weakness of the pre-war system crystallized in excessive deference to national sovereignty. Doctrinal efforts in the 1920s and 1930s were underlain by a critique of sovereignty that arose from three directions, emanating from traditions of domestic jurisprudence and political theory.

10  One critique was based on developments in German public law. Hans Kelsen’s pure theory of law made a fundamental distinction between the State as a sociological concentration of power and as a juridical concept. From a legal perspective, the State signified nothing but a legal order that was valid within a certain territory at a certain moment. The position of the State in the world translated legally into the question about the relationship between the domestic and the international legal orders. As it was a postulate of legal reason, indeed reason tout court (in short), that the two could not enjoy independent validity—for that would mean that some act could be both permitted and prohibited—one had to be superior to the other. Either international law was a mere reflection of national legal orders or vice versa. Kelsen regarded this choice as one of pure political value. He made no secret of his preference for the primacy of international law that was supported by pacifism and internationalism and from which sovereignty signified merely the competence that international law delegated to territorial authorities. Kelsen’s formalism was intellectually powerful but rarely adopted as a matter of constitutional practice. Most States continued to regard international law as binding on national authorities only to the extent that it had been incorporated in national law (International Law and Domestic [Municipal] Law). Preference for pacifism and internationalism was by no means self-evident among inter-war European elites.

11  Another attack linked sovereignty with legal positivism and came from a resurgent natural law in the 1920s. If the war had been caused by moral collapse, then it seemed natural to try to resuscitate moral principles—especially principles of Judeo-Christian ethics—into a foundation of European diplomacy. While some such as Alfred Verdross in Austria dressed this in a historical narrative about the emergence of an international community with an implicit moral ‘constitution’, others such as Louis Le Fur in France associated it with the need to return to the official doctrines of Catholicism. The problem with the many strands of natural law writing in this period was the old one: as long as the principles were stated in the abstract, they seemed unobjectionable, but as soon as they were cited in favour of this or that rule or institution, they immediately appeared to support some contested policy, or some nation, against another. The turn to natural law consolidated the profession’s self-image as part of a historical continuum that began with the Spanish Scholastics in the 16th and 17th centuries—Vitoria, Suarez—continuing from Grotius and Protestant natural law in the 17th and 18th centuries through the liberal humanitarianism of the 19th century. This narrative supported the profession’s sense of a historical ‘mission’ but failed to translate into concrete or widely accepted institutional blueprints.

12  A third attack on sovereignty joined French liberal solidarism with the sociological jurisprudence that developed in Germany in the 1920s. This was supported by an argument about the taming of nation States by the unifying laws of modernity and an increasingly interdependent economy (Interdependence). The most important academic international lawyer in France, Georges Scelle, argued that treaties and customs were binding only to the extent that they declared objective principles of social solidarity. National governments were local administrators of an intrinsically global system. International law was not an instrument of State policy but an expression of the general interest of humankind, always already united by the force of social necessity (Sociological Theories of International Law). The same message was delivered by Alejandro Alvarez from Chile who expressed it in terms of a fundamental transformation from an ‘old’ law of European-centred sovereign voluntarism to a ‘new’ law aiming to provide for the welfare of all the world’s peoples. The Swiss internationalist Max Huber articulated this view in a historical sociology about economic interdependence slowly doing away with nationalism as functional needs pushed into increasingly internationalized forms of government.

13  The critiques of sovereignty and support for international organizations were leading themes in the international law profession in the 1920s and 1930s (International Organizations or Institutions, General Aspects; International Organizations or Institutions, History of). But neither the critiques nor the constructive proposals emerged from unanimity about concrete policies in the League of Nations or elsewhere. Paradoxically, they could even be instrumentalized in support of domestic agendas and attacks on political adversaries. Hence they failed to bring about the kind of overall transformation their vocabularies suggested. Outside the university, most lawyers continued to participate in practical work in foreign ministries but increasingly also in international and domestic organizations, drafting manifestos, declarations, and sometimes treaties, even participating in arbitration or pleading before the Permanent Court of International Justice (PCIJ). A pragmatic sensibility about the tasks of the profession developed that was ambivalently related to the critical vocabularies proliferating in academic literature.

14  The radical nature of the critiques of sovereignty, and the critics’ own commitment to the institutions of the League of Nations turned against those kinds of work as the inter-war system collapsed. Influential analysts of the collapse—Raymond Aron in France, EH Carr in Britain, and Hans Morgenthau in Germany and the United States—all pointed to the apparently fantastic constructions of a ‘legalism’ or ‘idealism’ that had been oblivious to the ‘realities’ of power in the international world. After World War II, international legal imagination was heavily constrained by the wide acceptance of the ‘realist’ explanation of the failure of the inter-war system. Within the United Nations and during the long years of the Cold War, international law developed as a pragmatic sensibility, hoping to assist in the political and functional work undertaken in foreign ministries and international institutions (History of International Law, since World War II). An activist spirit re-emerged only with the new human rights and welfare regimes in the 1960s and thereafter, and in the debates on intervention in a new world order in the 1990s (Intervention, Prohibition of).

D.  The League of Nations and the Idea of the International Community

15  Consistent with their critique of sovereignty, international lawyers supported the creation of permanent international institutions for the purposes of maintaining peace, co-ordinating pacific settlement and organizing international co-operation for common objectives. Nevertheless, most European States viewed President Wilson’s proposal for a permanent League of Nations (‘League’) with some suspicion and it was only through Wilson’s personal insistence that the covenant was finally adopted in 1919 (Fourteen Points of Wilson [1918]). The League was received by international lawyers with divided attitudes. On the one hand, lawyers such as Scelle and Verdross interpreted it as a ground-breaking move towards an organized international legal community, a tangible step towards the federation of free republics that Kant had sketched in his 1795 essay Zum ewigen Frieden (Community Interest). On the other hand, the covenant was technically a part of the peace treaty dictated to the vanquished powers in a way that undermined its universal status and perpetuated war-time divisions. The original members of the League were 22 allied and associated powers plus 13 neutrals, while Germany joined in 1926 and the Soviet Union in 1934. German internationalists such as Hans Wehberg and Walther Schücking, as well as the German Foreign Ministry, supported constructive contribution by Germany in League organs so as to develop it in a more favourable direction. The majority of German lawyers, however, shared Carl Schmitt’s analysis of the League as an instrument of Anglo-American hegemony.

16  In practice, the League was severely hampered by its lack of universality, in part reflecting the principal European powers’ desire to ‘internationalize’ the colonial relationship within the League. Its Eurocentrism was highlighted by President Wilson’s failure to secure the US’ participation and by the weak role that non-Europeans enjoyed in League bodies. Japan never forgot the veto on its proposal to include a provision on racial equality in the covenant (Racial and Religious Discrimination). As troubles began in the 1930s, Japan, Italy, and Germany all withdrew from the organization, while the Soviet Union was expelled after its attack on Finland in 1939. League organs often failed to develop independence from the policies of the most powerful—Western—members in a way that had a significant effect on the League’s failure to attain the status of a true world organization.

17  Structurally speaking, the covenant left much to be desired. The unanimity rule covered most substantive decision-making in the two main political bodies, the Assembly and the Council. In the Manchurian crisis (1931–32), for example, Japan was able to prevent the Council from taking action for over a year, enabling it to consolidate the puppet government of Manchukuo. The main task of the Council was to deal with international disputes and it dealt with them largely as a standing conference of ambassadors. The League’s third main organ, the Secretariat, showed a high ethos of civil service but was rarely given room to manoeuvre with independence from Member States.

18  The main objective of the League was to keep international disputes from threatening peace and security by channelling them into avenues of pacific settlement. The technically complex provisions of the Covenant reflected the wide representation of lawyers in the delegations at Versailles. The covenant’s peace system was composed of five sets of provisions. The heart of these was Art. 10 Covenant of the League of Nations (‘League Covenant’) in which League members promised to guarantee each others’ territorial integrity and political independence. Understandably, the importance of this provision was stressed by small members while larger States such as Britain that were expected to make a reality of the guarantee remained sceptical. There was a widespread sense that the war had been caused by an uncontrolled arms race. Therefore, League members promised to reduce their armaments to ‘the lowest point consistent with national safety’ (Art. 8 League Covenant) with the expectation that the plans for this purpose would be adopted in due course by the Council (Disarmament). Third, there was a very developed system for the peaceful settlement of disputes. A distinction was made between ‘legal’ disputes to be submitted to the PCIJ and ‘political’ disputes directed to the Council. Members were expected to abide by the decisions while the opportunity to go to war against a State that did not do so was reserved as a guarantee of the system. A fourth element was sanctions (Art. 16 League Covenant)—the obligation on members to sever their trade relations immediately with a party that had gone to ‘war’ in violation of the covenant. Finally, Art. 19 League Covenant contained the famous provision on peaceful change that aimed to soften the strong emphasis on the maintenance of the status quo under the territorial guarantee.

19  In addition, the League Covenant also dealt with humanitarian matters. Alongside the administration of the colonies of the defeated countries as mandates, it was engaged in the supervision of the functioning of a certain number of treaties on minority protection, especially in Central and Northern Europe (Minority Protection System between World War I and World War II). Its activities extended likewise to co-operation in the fields of welfare, technology, labour, and the improvement of conditions of life. The League was also expected to become the umbrella under which the various international functional organizations would henceforth carry out their activities. These developments were understood by international lawyers in different ways. While some saw there little else than pragmatic inter-State co-ordination, others theorized about the emergence of an international administration of territories.

20  International lawyers were closely involved in League activities and participated in its experts groups and national delegations. For example, the French delegation was headed by former foreign minister, an international lawyer from the ‘solidarist’ camp, Léon Bourgeois, who also became the first president of the Council. Although lawyers disagreed about the exact nature of the League, by the end of the 1920s, the position had solidified that it was not simply a co-ordinating point for national diplomacy. Analogies from national law were often employed in legal analysis such as Hersch Lauterpacht’s argument from 1936 of the Covenant as ‘higher law’, that is to say, a kind of an international constitution.

21  The use of a legal—even constitutional—vocabulary in the analysis of the League did not automatically translate into the kind of ‘idealism’ that became the caricature pinned on inter-war law by successive generations. Behind that vocabulary was a political project to develop the League into a centralized administration of international affairs to give effect to modernity’s internationalizing trends. The lawyers were not unaware of the political difficulties and frequently enlisted their interpretations as parts of national agendas. It may be true as a historical matter that the League ‘existed only to help states do together what they could not so easily do alone. It never sought to do more. The watch-word was voluntarism through and through’ (Northedge 52). But for the lawyers, the League constituted a centre of the professional universe. There they could meet and seek to turn their shared ésprit d’internationalité into concrete projects of international governance and dispute settlement. The League’s decisions and other materials were formulated in legal terms that lent themselves to professional interpretation and systematization like acts of domestic authorities. Even as every text on the League began with the dictum that it was no super-State, that affirmation perhaps revealed a veiled hope that it would one day become something like such.

E.  The Rise and Fall of Collective Security

22  Few inter-war lawyers were pacifists. But most of them agreed with Kelsen and Lauterpacht that peace was an eminently legal postulate. Hence they sought to preserve peace by replacing the diplomatic system of balance of power by collective security under the League. This was an essentially legal system in that it depended on two rules, both conceived in a rather absolute manner: the prohibition of war and the duty to adopt sanctions against the covenant-breaker (International Organizations or Institutions, Supervision and Sanctions). The theory was that if the potential aggressor knew that it would be faced with the collective power of League members, it would be deterred from committing aggression. Every aspect of this depended on the automatic operation of the rules. Any discretion would immediately open the door for political speculation, bargaining and special arrangements.

23  None of this worked in practice. When Japan invaded Manchuria, members engaged in protracted debate about whether its actions qualified as war or mere police operation as it maintained. When Italy invaded Abyssinia in 1935–36, there was no doubt that the League Covenant obligated members to take immediate measures against it. Mussolini, however, declared that any embargo on oil—which was crucial for its war effort—would be considered as an act of war. The predominant concern of members in the spring of 1936 was to prevent the formation of the Mussolini-Hitler axis and disrupting their trade with Italy would have immediately led to that consequence. After the half-hearted measures were finally withdrawn in the summer of 1936, even those members that had until then sought to attain their security from the League turned to negotiate regional arrangements and bilateral non-aggression pacts instead.

24  Efforts to strengthen the Covenant’s peace system led nowhere. Neither the plan for a Mutual Assistance Pact to organize collective reaction nor the Geneva Protocol of 1925 providing for compulsory judicial settlement and action against a non-complying party were acceptable, owing in particular to the way in which they would have enlisted the British navy as world police—and the British were reluctant to provide an open-ended guarantee for this purpose. In the Kellogg Briand Pact (1928) parties renounced war as an instrument of national policy but duly reserved their ‘inherent right’ of self-defence. The Locarno Treaties (1925) in which Britain and Italy guaranteed the boundary between France, Germany, and Belgium was widely celebrated but in fact demonstrated that tangible security still depended on special political relationships—and opened embarrassing questions regarding the status of Germany’s eastern frontiers.

25  The question of neutrality under the League Covenant and especially the Kellogg-Briand Pact preoccupied lawyers extensively (Neutrality, Concept and General Rules). The League Assembly declared in 1920 that neutrality was in principle incompatible with the obligations of League members to take action against an aggressor. For lawyers such as Lauterpacht and Scelle, for example, members were no longer entitled to accord equivalent treatment to both belligerent powers. One would have to be understood as a law-breaker. However, it was unclear what followed from this principle, and many States adopted policies of neutrality during the period though their interpretation of the content of that neutrality—or ‘non-belligerency’—varied (Belligerency). The matter came to a head when the US adopted the lend-lease policy after the outbreak of World War II under which it could provide material assistance to countries that were victims of German aggression.

26  The move from the 19th century balance system to collective security under the League Covenant was an effort to move away from political manoeuvring to the application of legal rules. In practice, however, the rules could not be applied independently of political considerations: was some act war or aggression or was it police operation or self-defence? Ought sanctions really to be applied—or might their application only worsen the situation? The League system made every conflict a global conflict in a way that made little diplomatic or political sense. The lesson drawn by the drafters of the United Nations Charter was not that the League had failed although its peace system had been based on relatively clear rules. It had failed because those rules were so absolute and did not allow taking account of political considerations. This is why the prohibition of the use of force in Art. 2 (4) UN Charter is left open-ended (Use of Force, Prohibition of ) and discretion to decide when and how to react is delegated to the UN Security Council (United Nations, Security Council). Where the League Covenant sought to move from balance of power to collective security, the UN Charter re-established the search for balance between the five Great Powers inside the UN Security Council.

F.  International Co-operation

27  The inter-war years saw the development of theories of functional interdependence according to which the intensification of international co-operation in the most varied fields would strengthen the conditions of international peace and security. This provided justification for inclusion of work on the improvement of conditions of human welfare in the League Covenant (Art. 23 League Covenant) and for the integration of the various international bureaus and organizations that had been set up from mid-19th century onwards ‘under the direction of the League’ (Art. 24 League Covenant). That Part XIII of the Versailles Treaty established the International Labour Organization (ILO) as an independent organization reflected the common view that peace could be safeguarded only under conditions of social justice. ILO organs met on an annual basis and were composed of a tripartite representation of workers, employers, and government representatives. The ILO also adopted draft conventions on a number of topics related to conditions of work that were then submitted to Member States for ratification.

28  The work of organizing international co-operation through the instrumentality of the multilateral treaty continued both inside and outside the League (Co-operation, International Law of). As far as the League was concerned, this was sometimes justified by reference to Art. 19 League Covenant that authorized the revision of unjust treaties—though most lawyers saw the importance of this provision in the way it opened the door for adjusting the peace treaties (Treaties, Unequal). The work for the adoption of treaties in the field of trade, technological and scientific co-operation, communications, intellectual property rights, and so on continued in the 1920s and 1930s though many of the conventions received only a small number of parties and often failed to enter into force. Notable achievements were attained in the field of communications—eg the 1919 Paris Convention relating to the Regulation of Aerial Navigation; the 1921 Barcelona Convention and Statute on the Regime of Navigable Waterways of International Concern; the 1927 and 1932 Washington and Madrid Conventions on Radiotelegraphic and Telecommunication Cooperation; and the 1923 Geneva Conventions and Statutes on the International Regime of Maritime Ports and the International Regime for Railways (International Watercourses; Telecommunications, International Regulation). In general, results of the development of international humanitarian law during the inter-war era were less than impressive. A convention on chemical weapons was adopted in 1925 and so were the 1929 Red Cross Conventions relative to the Treatment of Prisoners of War and for the Amelioration of the Condition of the Wounded and Sick in Armies in the Field (Chemical Weapons and Warfare; Prisoners of War; Wounded, Sick and Shipwrecked).

29  In the commercial and monetary fields, League organs propagated principles of free trade against increasing protectionist tendencies, especially after the onset of the economic crisis in 1929 (Free Trade Areas). Commercial treaties continued to operate rather as they had done in the 19th century though problems in the functioning of the most-favoured-nation clause became a continuous conference topic and the crisis in the application of the gold standard from 1931 onwards led to various efforts to safeguard the conditions of payment, all more or less of a temporary duration.

30  The principle of self-determination propagated by President Wilson was in European practice translated into a network of minority treaties whose operation was in principle surveyed by League organs. However, the operation of the treaties in Central and Southern Europe created constant problems and prolonged a sense of injustice between the populations. But the sense that territorial power needed to be grounded on something like affective and legitimate authority—consolidated in the Palmas Island Arbitration—could no longer be dispensed with. It provided a legal translation for the sentiment of nationalism that could carry many kinds of political demands that worked against the federal project to which most international lawyers were committed.

31  In 1930 a conference on the codification of key aspects of international law took place under League auspices in The Hague. The conference had before it drafts on the law of State responsibility, territorial waters (Territorial Sea), and the reduction of statelessness (Stateless Persons) but failed to attain results on any of these matters. For many international lawyers who had participated in the preparatory work for the conference, this was a grave disappointment and signified the end of efforts to advance a universal international law through the ‘sadly overworked’ (McNair [1961] 739) instrumentality of the multilateral treaty.

G.  Europe, United States, and the Wider World

32  The Great War turned the interest of European populations to reconstruction at home and away from imperial pursuits abroad. The colonial acquisitions that had been consolidated at the end of the 19th century in the formal protectorates and various types of informal suzerainty remained, but without a sense of their representing a joint civilizing project (Colonialism). Anglo-American predominance never translated into formal empire but was exercised as informal influence through trade, diplomacy, and intergovernmental organization, including through the League. Although five British dominions (Australia, Canada, India, New Zealand, South Africa) entered the League still as parts of the British Empire, at least the white settlement colonies decided their policies themselves and with the Statute of Westminster (1931) received also formal independence. India, however, remained a British dependency until 1947.

33  One interesting innovation in the covenant was the mandates system inaugurated under Art. 22 League Covenant that divested Germany and Turkey of their dependent territories in Africa, the Middle East, and the Pacific. These had a joint population of over 20 million and they were allocated to certain of the victorious powers to be administered under League supervision. The territories were divided into three classes according to their level of cultural and political development—the so-called A, B, and C mandates—of which those in the first group were to be prepared for independence while those in the latter—mainly African and Pacific territories—were to be protected against abuses. It was through this system that Iraq received its independence in 1932. Supervision was organized through reports submitted by the Mandatory to a Permanent Mandates Commission in Geneva. The system was a compromise between direct annexation and full international administration. The Mandates were to be treated as a ‘sacred trust of civilization’—that is to say, as an enlightened form of colonial administration—but in practice Mandatory States often behaved much as they did in their own colonial possessions.

34  Despite the League’s Europe-centredness, among the original members were 11 Latin American States plus China, Japan, Liberia, and Siam. Later it was joined by more non-European States although their influence remained small. In the Western hemisphere, a movement towards regionalism had been formalized in 1890 by the establishment of the International Union of American Republics with a centre in Washington (Regional Co-operation). Though in some part an offshoot of the hegemonic arrangement based on the Monroe doctrine—which was officially approved in the League Covenant—it also provided a forum for legal initiatives to further the Co-operation between Latin American States. From 1928 onwards the International Union of American Republic produced a number of multilateral treaties among which was the Anti-War Pact on Non-Aggression and Conciliation of 1933 (Saavedra Lamas Treaty [1933]) that was supposed to supplement the Kellogg-Briand Pact. Treaties were also concluded on various aspects of commercial and legal co-operation as well as on the rights and duties of States in the region. South American international lawyers such as Alvarez participated actively and visibly in the work of the League and in other forms of legal Co-operation propagating the special contribution that American States had to offer for the modernization of international law and organization. Nevertheless, the effects of this type of regionalism remained limited.

35  The Soviet Union was initially left outside the League but joined in 1934 as a result of the manoeuvring of its active foreign minister Maxim Litvinov. The Soviet State initially repudiated all agreements by the Czarist regime and opposed international law as part of an international system in which the revolutionary State could take no part. Nevertheless, in doctrine and practice, the Soviet position changed in function of the needs of Soviet foreign policy and the socialist State began to enter commercial and technical agreements with other States while simultaneously carrying out revolutionary activities through the Comintern.

36  Hitler’s seizure of power in Germany in 1933 sharpened the conflict between Germany’s insistence on being treated equally with other League members and the French obsession with security. In the autumn of 1933 Germany declared its withdrawal from the League. In 1936 the Rhineland was remilitarized by Germany against its obligations under the Versailles Treaty while the Anschluss of 1938 violated what the PCIJ had earlier said about Austria’s duty not to ‘alienate’ its independence (Customs Regime between Germany and Austria [Advisory Opinion]).

H.  International Jurisdiction

37  The PCIJ was established in 1922. It was called upon to apply treaties, customary international law, and the general principles of law recognized by civilized nations—a reference that meant that if no treaty covered a matter and it was it impossible to find a settled custom, the Court should still not pronounce non liquet and instead seek to find the basis for its judgments from domestic analogies and natural law (General Principles of Law). During 1922–39 the Court decided altogether 29 contentious cases and gave 27 advisory opinions. The Court was the first permanent international tribunal with a statute that had been adopted by a multilateral treaty, and with fixed procedures and sessions (International Courts and Tribunals). Its establishment carried great symbolic meaning and its jurisprudence became the object of an expansive academic commentary, thus contributing to the concretization of international legal rules and principles. Many of the cases clarified key doctrines and legal institutions in what has turned out to be a permanent way although some—such as the 1931 Austro-German Customs Union Case—were eminently political and thus settled less successfully. Efforts to develop compulsory jurisdiction and to expand the Court’s jurisdiction were made both nationally and within the League—especially through the abortive Geneva Protocol of 1924 and the General Act of 1928. Towards the end of the 1930s, however, these efforts were gradually given up.

I.  Conclusion

38  The image of international law in the inter-war period is heavily coloured by the political realist interpretation, produced in the 1940s and 1950s, according to which however brilliant the legal constructions, there was something in them that almost by necessity made them fail. There is a germ of truth in that view, of course, but it ought to be met by two rejoinders. First, post-war ‘realism’ always downplayed the extent to which its success could be credited to an ethos of prudence that played upon ideas about human nature and the structure of the international world that were no less abstract and ‘ideological’ than those of the inter-war lawyers, only different. As a post-war sensibility realism was understandable as a fall-back from the earlier activism and optimism, but as the time for constructive projects re-emerged, realism was frustrating in its conservative bias, and downright unhelpful for resolving conflicts framed in terms of normative preferences.

39  Second, the standpoint of the immediate post-war moment may not be adequate to capture the meaning of the efforts under way in many fields before the war to think of international social life beyond the sovereign State. The seeds of World War II were sown by the peace of 1919, and the efforts of the lawyers were not adequate for grappling with contingencies as they arose. But those are hardly the terms in which they should be understood. Those efforts were a logical continuation of aspects of 19th century liberal internationalism, even the ethos of the European Enlightenment that looked towards a universal federation of free republics. As an institutional project, it is possible to dismiss this as a wholly utopian idea. But as a horizon of political action, and a standard of criticism of any existing structure of institutional power, it remains indispensable as part of any defensible politics of universal law.

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