Definition and scope
According to Bentham’s classic definition, international law is a collection of rules governing relations between states. It is a mark of how far international law has evolved that this original definition omits individuals and international organizations—two of the most dynamic and vital elements of modern international law. Furthermore, it is no longer accurate to view international law as simply a collection of rules; rather, it is a rapidly developing complex of rules and influential—though not directly binding—principles, practices, and assertions coupled with increasingly sophisticated structures and processes. In its broadest sense, international law provides normative guidelines as well as methods, mechanisms, and a common conceptual language to international actors—i.e., primarily sovereign states but also increasingly international organizations and some individuals. The range of subjects and actors directly concerned with international law has widened considerably, moving beyond the classical questions of war, peace, and diplomacy to include human rights, economic and trade issues, space law, and international organizations. Although international law is a legal order and not an ethical one, it has been influenced significantly by ethical principles and concerns, particularly in the sphere of human rights.
International law is distinct from international comity, which comprises legally nonbinding practices adopted by states for reasons of courtesy (e.g., the saluting of the flags of foreign warships at sea). In addition, the study of international law, or public international law, is distinguished from the field of conflict of laws, or private international law, which is concerned with the rules of municipal law—as international lawyers term the domestic law of states—of different countries where foreign elements are involved.
International law is an independent system of law existing outside the legal orders of particular states. It differs from domestic legal systems in a number of respects. For example, although the United Nations (UN) General Assembly, which consists of representatives of some 190 countries, has the outward appearances of a legislature, it has no power to issue binding laws. Rather, its resolutions serve only as recommendations—except in specific cases and for certain purposes within the UN system, such as determining the UN budget, admitting new members of the UN, and, with the involvement of the Security Council, electing new judges to the International Court of Justice (ICJ). Also, there is no system of courts with comprehensive jurisdiction in international law. The ICJ’s jurisdiction in contentious cases is founded upon the consent of the particular states involved. There is no international police force or comprehensive system of law enforcement, and there also is no supreme executive authority. The UN Security Council may authorize the use of force to compel states to comply with its decisions, but only in specific and limited circumstances; essentially, there must be a prior act of aggression or the threat of such an act. Moreover, any such enforcement action can be vetoed by any of the council’s five permanent members (China, France, Russia, the United Kingdom, and the United States). Because there is no standing UN military, the forces involved must be assembled from member states on an ad hoc basis.
International law is a distinctive part of the general structure of international relations. In contemplating responses to a particular international situation, states usually consider relevant international laws. Although considerable attention is invariably focused on violations of international law, states generally are careful to ensure that their actions conform to the rules and principles of international law, because acting otherwise would be regarded negatively by the international community. The rules of international law are rarely enforced by military means or even by the use of economic sanctions. Instead, the system is sustained by reciprocity or a sense of enlightened self-interest. States that breach international rules suffer a decline in credibility that may prejudice them in future relations with other states. Thus, a violation of a treaty by one state to its advantage may induce other states to breach other treaties and thereby cause harm to the original violator. Furthermore, it is generally realized that consistent rule violations would jeopardize the value that the system brings to the community of states, international organizations, and other actors. This value consists in the certainty, predictability, and sense of common purpose in international affairs that derives from the existence of a set of rules accepted by all international actors. International law also provides a framework and a set of procedures for international interaction, as well as a common set of concepts for understanding it.
Historical development
International law reflects the establishment and subsequent modification of a world system founded almost exclusively on the notion that independent sovereign states are the only relevant actors in the international system. The essential structure of international law was mapped out during the European Renaissance, though its origins lay deep in history and can be traced to cooperative agreements between peoples in the ancient Middle East. Among the earliest of these agreements were a treaty between the rulers of Lagash and Umma (in the area of Mesopotamia) in approximately 2100 bce and an agreement between the Egyptian pharaoh Ramses II and Hattusilis III, the king of the Hittites, concluded in 1258 bce. A number of pacts were subsequently negotiated by various Middle Eastern empires. The long and rich cultural traditions of ancient Israel, the Indian subcontinent, and China were also vital in the development of international law. In addition, basic notions of governance, of political relations, and of the interaction of independent units provided by ancient Greek political philosophy and the relations between the Greek city-states constituted important sources for the evolution of the international legal system.
Many of the concepts that today underpin the international legal order were established during the Roman Empire. The jus gentium (Latin: “law of nations”), for example, was invented by the Romans to govern the status of foreigners and the relations between foreigners and Roman citizens. In accord with the Greek concept of natural law, which they adopted, the Romans conceived of the jus gentium as having universal application. In the Middle Ages, the concept of natural law, infused with religious principles through the writings of the Jewish philosopher Moses Maimonides (1135–1204) and the theologian St. Thomas Aquinas (1224/25–1274), became the intellectual foundation of the new discipline of the law of nations, regarded as that part of natural law that applied to the relations between sovereign states.
After the collapse of the western Roman Empire in the 5th century ce, Europe suffered from frequent warring for nearly 500 years. Eventually, a group of nation-states emerged, and a number of supranational sets of rules were developed to govern interstate relations, including canon law, the law merchant (which governed trade), and various codes of maritime law—e.g., the 12th-century Rolls of Oléron, named for an island off the west coast of France, and the Laws of Wisby (Visby), the seat of the Hanseatic League until 1361. In the 15th century the arrival of Greek scholars in Europe from the collapsing Byzantine Empire and the introduction of the printing press spurred the development of scientific, humanistic, and individualist thought, while the expansion of ocean navigation by European explorers spread European norms throughout the world and broadened the intellectual and geographic horizons of western Europe. The subsequent consolidation of European states with increasing wealth and ambitions, coupled with the growth in trade, necessitated the establishment of a set of rules to regulate their relations. In the 16th century the concept of sovereignty provided a basis for the entrenchment of power in the person of the king and was later transformed into a principle of collective sovereignty as the divine right of kings gave way constitutionally to parliamentary or representative forms of government. Sovereignty also acquired an external meaning, referring to independence within a system of competing nation-states.
Early writers who dealt with questions of governance and relations between nations included the Italian lawyers Bartolo da Sassoferrato (1313/14–1357), regarded as the founder of the modern study of private international law, and Baldo degli Ubaldi (1327–1400), a famed teacher, papal adviser, and authority on Roman and feudal law. The essence of the new approach, however, can be more directly traced to the philosophers of the Spanish Golden Age of the 16th and 17th centuries. Both Francisco de Vitoria (1486–1546), who was particularly concerned with the treatment of the indigenous peoples of South America by the conquering Spanish forces, and Francisco Suárez (1548–1617) emphasized that international law was founded upon the law of nature. In 1598 Italian jurist Alberico Gentili (1552–1608), considered the originator of the secular school of thought in international law, published De jure belli libri tres (1598; Three Books on the Law of War), which contained a comprehensive discussion of the laws of war and treaties. Gentili’s work initiated a transformation of the law of nature from a theological concept to a concept of secular philosophy founded on reason. The Dutch jurist Hugo Grotius (1583–1645) has influenced the development of the field to an extent unequaled by any other theorist, though his reputation as the father of international law has perhaps been exaggerated. Grotius excised theology from international law and organized it into a comprehensive system, especially in De Jure Belli ac Pacis (1625; On the Law of War and Peace). Grotius emphasized the freedom of the high seas, a notion that rapidly gained acceptance among the northern European powers that were embarking upon extensive missions of exploration and colonization around the world.
The scholars who followed Grotius can be grouped into two schools, the naturalists and the positivists. The former camp included the German jurist Samuel von Pufendorf (1632–94), who stressed the supremacy of the law of nature. In contrast, positivist writers, such as Richard Zouche (1590–1661) in England and Cornelis van Bynkershoek (1673–1743) in the Netherlands, emphasized the actual practice of contemporary states over concepts derived from biblical sources, Greek thought, or Roman law. These new writings also focused greater attention on the law of peace and the conduct of interstate relations than on the law of war, as the focus of international law shifted away from the conditions necessary to justify the resort to force in order to deal with increasingly sophisticated interstate relations in areas such as the law of the sea and commercial treaties. The positivist school made use of the new scientific method and was in that respect consistent with the empiricist and inductive approach to philosophy that was then gaining acceptance in Europe. Elements of both positivism and natural law appear in the works of the German philosopher Christian Wolff (1679–1754) and the Swiss jurist Emerich de Vattel (1714–67), both of whom attempted to develop an approach that avoided the extremes of each school. During the 18th century, the naturalist school was gradually eclipsed by the positivist tradition, though, at the same time, the concept of natural rights—which played a prominent role in the American and French revolutions—was becoming a vital element in international politics. In international law, however, the concept of natural rights had only marginal significance until the 20th century.
Positivism’s influence peaked during the expansionist and industrial 19th century, when the notion of state sovereignty was buttressed by the ideas of exclusive domestic jurisdiction and nonintervention in the affairs of other states—ideas that had been spread throughout the world by the European imperial powers. In the 20th century, however, positivism’s dominance in international law was undermined by the impact of two world wars, the resulting growth of international organizations—e.g., the League of Nations, founded in 1919, and the UN, founded in 1945—and the increasing importance of human rights. Having become geographically international through the colonial expansion of the European powers, international law became truly international in the first decades after World War II, when decolonization resulted in the establishment of scores of newly independent states. The varying political and economic interests and needs of these states, along with their diverse cultural backgrounds, infused the hitherto European-dominated principles and practices of international law with new influences.
The development of international law—both its rules and its institutions—is inevitably shaped by international political events. From the end of World War II until the 1990s, most events that threatened international peace and security were connected to the Cold War between the Soviet Union and its allies and the U.S.-led Western alliance. The UN Security Council was unable to function as intended, because resolutions proposed by one side were likely to be vetoed by the other. The bipolar system of alliances prompted the development of regional organizations—e.g., the Warsaw Pact organized by the Soviet Union and the North Atlantic Treaty Organization (NATO) established by the United States—and encouraged the proliferation of conflicts on the peripheries of the two blocs, including in Korea, Vietnam, and Berlin. Furthermore, the development of norms for protecting human rights proceeded unevenly, slowed by sharp ideological divisions.
The Cold War also gave rise to the coalescence of a group of nonaligned and often newly decolonized states, the so-called “Third World,” whose support was eagerly sought by both the United States and the Soviet Union. The developing world’s increased prominence focused attention upon the interests of those states, particularly as they related to decolonization, racial discrimination, and economic aid. It also fostered greater universalism in international politics and international law. The ICJ’s statute, for example, declared that the organization of the court must reflect the main forms of civilization and the principal legal systems of the world. Similarly, an informal agreement among members of the UN requires that nonpermanent seats on the Security Council be apportioned to ensure equitable regional representation; 5 of the 10 seats have regularly gone to Africa or Asia, two to Latin America, and the remainder to Europe or other states. Other UN organs are structured in a similar fashion.
The collapse of the Soviet Union and the end of the Cold War in the early 1990s increased political cooperation between the United States and Russia and their allies across the Northern Hemisphere, but tensions also increased between states of the north and those of the south, especially on issues such as trade, human rights, and the law of the sea. Technology and globalization—the rapidly escalating growth in the international movement in goods, services, currency, information, and persons—also became significant forces, spurring international cooperation and somewhat reducing the ideological barriers that divided the world, though globalization also led to increasing trade tensions between allies such as the United States and the European Union (EU).
Since the 1980s, globalization has increased the number and sphere of influence of international and regional organizations and required the expansion of international law to cover the rights and obligations of these actors. Because of its complexity and the sheer number of actors it affects, new international law is now frequently created through processes that require near-universal consensus. In the area of the environment, for example, bilateral negotiations have been supplemented—and in some cases replaced—by multilateral ones, transmuting the process of individual state consent into community acceptance. Various environmental agreements and the Law of the Sea treaty (1982) have been negotiated through this consensus-building process. International law as a system is complex. Although in principle it is “horizontal,” in the sense of being founded upon the concept of the equality of states—one of the basic principles of international law—in reality some states continue to be more important than others in creating and maintaining international law.
International law and municipal law
In principle, international law operates only at the international level and not within domestic legal systems—a perspective consistent with positivism, which recognizes international law and municipal law as distinct and independent systems. Conversely, advocates of natural law maintain that municipal and international law form a single legal system, an approach sometimes referred to as monism. Such a system, according to monists, may arise either out of a unified ethical approach emphasizing universal human rights or out of a formalistic, hierarchical approach positing the existence of one fundamental norm underpinning both international law and municipal law.
A principle recognized both in international case law (e.g., the Alabama claims case between the United States and the United Kingdom following the American Civil War) and in treaties (e.g., Article 27 of the 1969 Vienna Convention on the Law of Treaties) is that no municipal rule may be relied upon as a justification for violating international law. The position of international law within municipal law is more complex and depends upon a country’s domestic legislation. In particular, treaties must be distinguished from customary international law. Treaties are written agreements that are signed and ratified by the parties and binding on them. Customary international law consists of those rules that have arisen as a consequence of practices engaged in by states.
The Constitution of the United States stipulates (Article VI, Section 2) that treaties “shall be the supreme Law of the Land.” Treaties are negotiated by the president but can be ratified only with the approval of two-thirds of the Senate (Article II)—except in the case of executive agreements, which are made by the president on his own authority. Further, a treaty may be either self-executing or non-self-executing, depending upon whether domestic legislation must be enacted in order for the treaty to enter into force. In the United States, self-executing treaties apply directly as part of the supreme law of the land without the need for further action. Whether a treaty is deemed to be self-executing depends upon the intention of the signatories and the interpretation of the courts. In Sei Fujii v. State of California (1952), for example, the California Supreme Court held that the UN Charter was not self-executing because its relevant principles concerning human rights lacked the mandatory quality and certainty required to create justiciable rights for private persons upon its ratification; since then the ruling has been consistently applied by other courts in the United States. In contrast, customary international law was interpreted as part of federal law in the Paquette Habana case (1900), in which the U.S. Supreme Court ruled that international law forbade the U.S. Navy from selling, as prizes of war, Cuban fishing vessels it had seized. Domestic legislation is supreme in the United States even if it breaches international law, though the government may be held liable for such a breach at the international level. In order to mitigate such a possibility, there is a presumption that the U.S. Congress will not legislate contrary to the country’s international obligations.
The United Kingdom takes an incorporationist view, holding that customary international law forms part of the common law. British law, however, views treaties as purely executive, rather than legislative, acts. Thus, a treaty becomes part of domestic law only if relevant legislation is adopted. The same principle applies in other countries where the English common law has been accepted (e.g., the majority of Commonwealth states and Israel). Although the incorporationist view regards customary law as part of the law of the land and presumes that municipal laws should not be inconsistent with international law, municipal laws take precedence over international law in cases of conflict. Those common-law countries that have adopted a written constitution generally have taken slightly different positions on the incorporation of international law into municipal law. Ireland’s constitution, for example, states that the country will not be bound by any treaty involving public funds without the consent of the national legislature, and in Cyprus treaties concluded in accordance with its constitution have a status superior to municipal law on the condition of reciprocity.
In most civil-law countries, the adoption of a treaty is a legislative act. The relationship between municipal and international law varies, and the status of an international treaty within domestic law is determined by the country’s constitutional provisions. In federal systems, the application of international law is complex, and the rules of international law are generally deemed to be part of the federal law. Although a treaty generally becomes operative only when it has been ratified by a national legislature, EU countries have agreed that regulations and decisions emanating from EU institutions are directly applicable and enforceable without the need for enabling legislation—except for legislation permitting this form of lawmaking, which is adopted upon the country’s entry into the union (e.g., Britain’s adoption of the European Communities Act in 1972).
Sources of international law
Article 38 (1) of the ICJ’s statute identifies three sources of international law: treaties, custom, and general principles. Because the system of international law is horizontal and decentralized, the creation of international laws is inevitably more complicated than the creation of laws in domestic systems.
Treaties
Treaties are known by a variety of terms—conventions, agreements, pacts, general acts, charters, and covenants—all of which signify written instruments in which the participants (usually but not always states) agree to be bound by the negotiated terms. Some agreements are governed by municipal law (e.g., commercial accords between states and international enterprises), in which case international law is inapplicable. Informal, nonbinding political statements or declarations are excluded from the category of treaties.
Treaties may be bilateral or multilateral. Treaties with a number of parties are more likely to have international significance, though many of the most important treaties (e.g., those emanating from Strategic Arms Limitation Talks) have been bilateral. A number of contemporary treaties, such as the Geneva Conventions (1949) and the Law of the Sea treaty (1982; formally the United Nations Convention on the Law of the Sea), have more than 150 parties to them, reflecting both their importance and the evolution of the treaty as a method of general legislation in international law. Other significant treaties include the Convention on the Prevention and Punishment of the Crime of Genocide (1948), the Vienna Convention on Diplomatic Relations (1961), the Antarctic Treaty (1959), and the Rome Statute establishing the International Criminal Court (1998). Whereas some treaties create international organizations and provide their constitutions (e.g., the UN Charter of 1945), others deal with more mundane issues (e.g., visa regulations, travel arrangements, and bilateral economic assistance).
Countries that do not sign and ratify a treaty are not bound by its provisions. Nevertheless, treaty provisions may form the basis of an international custom in certain circumstances, provided that the provision in question is capable of such generalization or is “of a fundamentally norm-creating character,” as the ICJ termed the process in the North Sea Continental Shelf cases (1969). A treaty is based on the consent of the parties to it, is binding, and must be executed in good faith. The concept known by the Latin formula pacta sunt servanda (“agreements must be kept”) is arguably the oldest principle of international law. Without such a rule, no international agreement would be binding or enforceable. Pacta sunt servanda is directly referred to in many international agreements governing treaties, including the Vienna Convention on the Law of Treaties (1969), which concerns treaties between states, and the Vienna Convention on the Law of Treaties Between States and International Organizations or Between International Organizations (1986).
