international law

international law

international law, body of rules considered legally binding in the relations between national states, also known as the law of nations. It is sometimes called public international law in contrast to private international law (or conflict of laws), which regulates private legal affairs affected by more than one jurisdiction.

Nature and Scope

International law includes both the customary rules and usages to which states have given express or tacit assent and the provisions of ratified treaties and conventions. International law is directly and strongly influenced, although not made, by the writings of jurists and publicists, by instructions to diplomatic agents, by important conventions even when they are not ratified, and by arbitral awards. The decisions of the International Court of Justice and of certain national courts, such as prize courts, are considered by some theorists to be a part of international law. In many modern states, international law is by custom or statute regarded as part of national (or, as it is usually called, municipal) law. In addition, municipal courts will, if possible, interpret municipal law so as to give effect to international law.

Because there is no sovereign supernational body to enforce international law, some older theorists, including Thomas Hobbes, Samuel Pufendorf, and John Austin have denied that it is true law. Nevertheless, international law is recognized as law in practice, and the sanctions for failing to comply, although often less direct, are similar to those of municipal law; they include the force of public opinion, self-help, intervention by third-party states, the sanctions of international organizations such as the United Nations, and, in the last resort, war.

National states are fundamentally the entities with which international law is concerned, although in certain cases municipal law may impose international duties upon private persons, e.g, the obligation to desist from piracy. New rights and duties have been imposed on individuals within the framework of international law by the decisions in the war crimes trials as well as the treaty establishing the International Criminal Court (see war crimes), by the genocide convention, and by the Declaration of Human Rights (see Economic and Social Council).

See also international relations.

Evolution of International Law


There was little scope for an international law in the period of ancient and medieval empires, and its modern beginnings coincide, therefore, with the rise of national states after the Middle Ages. Rules of maritime intercourse and rules respecting diplomatic agents (see diplomatic service) soon came into existence. At the beginning of the 17th cent., the great multitude of small independent states, which were finding international lawlessness intolerable, prepared the way for the favorable reception given to the De jure belli ac pacis [concerning the law of war and peace] (1625) of Hugo Grotius, the first comprehensive formulation of international law. Though not formally accepted by any nation, his opinions and observations were afterward regularly consulted, and they often served as a basis for reaching agreement in international disputes. The most significant principle he enunciated was the notion of sovereignty and legal equality of all states. Other important writers on international law were Cornelius van Bynkershoek, Georg F. von Martens, Christian von Wolff, and Emerich Vattel.

Development to World War I

The growth of international law came largely through treaties concluded among states accepted as members of the "family of nations," which first included the states of Western Europe, then the states of the New World, and, finally, the states of Asia and other parts of the world. The United States contributed much to the laws of neutrality and aided in securing recognition of the doctrine of freedom of the seas (see seas, freedom of the). The provisions of international law were ignored in the Napoleonic period, but the Congress of Vienna (see Vienna, Congress of) reestablished and added much, particularly in respect to international rivers and the classification and treatment of diplomatic agents. The Declaration of Paris (see Paris, Declaration of) abolished privateering, drew up rules of contraband, and stipulated rules of blockade. The Geneva Convention (1864) provided for more humane treatment of the wounded. The last quarter of the 19th cent. saw many international conventions concerning prisoners of war, communication, collision and salvage at sea, protection of migrating bird and sea life, and suppression of prostitution. Resort to arbitration of disputes became more frequent. The lawmaking conventions of the Hague Conferences represent the chief development of international law before World War I. The Declaration of London (see London, Declaration of) contained a convention of prize law, which, although not ratified, is usually followed. At the Pan-American Congresses, many lawmaking agreements affecting the Western Hemisphere have been signed.

Effect of the World Wars

In World War I, no strong nations remained on the sidelines to give effective backing to international law, and the concept of third party arbitration was again endangered; many of the standing provisions of international law were violated. New modes of warfare presented new problems in the laws of war, but attempts after the war to effect disarmament and to prohibit certain types of weapons (see war, laws of) failed, as the outbreak and course of World War II showed. The end of hostilities in 1945 saw the world again faced with grave international problems, including rectification of boundaries, care of refugees, and administration of the territory of the defeated enemy (see trusteeship, territorial). The inadequacy of the League of Nations and of such idealistic renunciations of war as the Kellogg-Briand Pact led to the formation of the United Nations as a body capable of compelling obedience to international law and maintaining peace. After World War II, a notable advance in international law was the definition and punishment of war crimes. Attempts at a general codification of international law, however, proceeded slowly under the International Law Commission established in 1947 by the United Nations.

Recent Developments

The nuclear age and the space age have led to new developments in international law. The basis of space law was developed in the 1960s under United Nations auspices. Treaties have been signed mandating the internationalization of outer space (1967) and other celestial bodies (1979). The 1963 limited test ban treaty (see disarmament, nuclear) prohibited nuclear tests in the atmosphere, in outer space, and underwater. The nuclear nonproliferation treaty (1968) attempted to limit the spread of nuclear weapons. The agreements of the Strategic Arms Limitation Talks, signed by the United States and the USSR in 1972, limited defensive and offensive weapon systems. This was first of many international arms treaties signed between the two nations until the dissolution of the Soviet Union. Other treaties have covered the internationalization of Antarctica (1959), narcotic interdiction (1961), satellite communications (1963), and terrorism (1973). The Law of the Sea (1983) clarified the status of territorial waters and the exploitation of the seabed. Environmental issues have led to a number of international treaties, including agreements covering fisheries (1958), endangered species (1973), global warming and biodiversity (1992). Since the signing of the General Agreement on Tariffs and Trade (GATT) in 1947, there have been numerous international trade agreements. The European Union (prior to 1993, the European Community) has made moves toward the establishment of a regional legal system; in 1988 a Court of First Instance was established to serve as a court of original jurisdiction on certain economic matters. The establishment of the International Criminal Court (2002), with jurisdiction over war crimes, crimes against humanity, and related matters, marked a major step forward in international law despite the United States' repudiation of the treaty under President George W. Bush.


For a collection of texts by early writers, see J. B. Scott, ed., Classics of International Law (12 vol., 1911-27). See also H. Lauterpacht, International Law: The Law of Peace (4 vol., 1970-78); A. D'Amato, International Law (1987); L. Henkin et al., International Law (2d ed. 1987); R. A. Falk, Revitalizing International Law (1989); D. P. Moynihan, The Law of Nations (1990).

Public international law concerns the structure and conduct of states and intergovernmental organizations. To a lesser degree, international law also may affect multinational corporations and individuals, an impact increasingly evolving beyond domestic legal interpretation and enforcement. Public international law has increased in use and importance vastly over the twentieth century, due all to the increase in global trade, armed conflict, environmental deterioration on a worldwide scale, awareness of human rights violations, rapid and vast increases in international transportation and a boom in global communications.

Public international law is sometimes called the "law of nations". It should not be confused with "private international law", which is concerned with the resolution of conflict of laws. In its most general sense, international law "consists of rules and principles of general application dealing with the conduct of states and of intergovernmental organizations and with their relations inter se, as well as with some of their relations with persons, whether natural or juridical.

The scope of public international law

Public international law establishes the framework and the criteria for identifying states as the principal actors in the international legal system. As the existence of a state presupposes control and jurisdiction over territory, international law deals with the acquisition of territory, state immunity and the legal responsibility of states in their conduct with each other. International law is similarly concerned with the treatment of individuals within state boundaries. There is thus a comprehensive regime dealing with group rights, the treatment of aliens, the rights of refugees, international crimes, nationality problems, and human rights generally. It further includes the important functions of the maintenance of international peace and security, arms control, the pacific settlement of disputes and the regulation of the use of force in international relations. Even when the law is not able to stop the outbreak of war, it has developed principles to govern the conduct of hostilities and the treatment of prisoners. International law is also used to govern issues relating to the global environment, the global commons such as international waters and outer space, global communications, and world trade.

Whilst municipal law is hierarchical or vertical in its structure (meaning that a legislature enacts binding legislation), international law is horizontal in nature. This means that all states are sovereign and theoretically equal. As a result of the notion of sovereignty, the value and authority of international law is dependent upon the voluntary participation of states in its formulation, observance, and enforcement. Although there may be exceptions, it is thought by many international academics that most states enter into legal commitments with other states out of enlightened self-interest rather than adherence to a body of law that is higher than their own. As D. W. Greig notes, "international law cannot exist in isolation from the political factors operating in the sphere of international relations".

Breaches of international law raise difficult questions for lawyers. Since international law has no established compulsory judicial system for the settlement of disputes or a coercive penal system, it is not as straightforward as managing breaches within a domestic legal system. However, there are means by which breaches are brought to the attention of the international community and some means for resolution. For example, there are judicial or quasi-judicial tribunals in international law in certain areas such as trade and human rights. The formation of the United Nations, for example, created a means for the world community to enforce international law upon members that violate its charter through the Security Council.

Traditionally, states and the Holy See were the sole subjects of international law. With the proliferation of international organizations over the last century, they have in some cases been recognized as relevant parties as well. Recent interpretations of international human rights law, international humanitarian law, and international trade law (e.g., North American Free Trade Agreement (NAFTA) Chapter 11 actions) have been inclusive of corporations, and even of certain individuals.

History of public international law

The earliest known treatise on international law was the Introduction to the Law of Nations written at the end of the 8th century by Muhammad al-Shaybani (d. 804), a jurist of the Hanafi school of Islamic law and jurisprudence, and other Islamic jurists soon followed with a number of treatises written on international law (Siyar in Arabic). These early Islamic legal treatises covered the application of Islamic ethics, Islamic economic jurisprudence and Islamic military jurisprudence to international law, and were concerned with a number of international law topics, including the law of treaties; the treatment of diplomats, hostages, refugees and prisoners of war; the right of asylum; conduct on the battlefield; protection of women, children and non-combatant civilians; contracts across the lines of battle; the use of poisonous weapons; and devastation of enemy territory. The first European treatise on international law was later written by Hugo Grotius in the early 17th century. He and other European legal scholars may have been influenced by early Islamic international law.

Beginning with the Peace of Westphalia in 1648, the 17th, 18th and 19th centuries saw the growth of the concept of the sovereign "nation-state", which consisted of a nation controlled by a centralized system of government. The concept of nationalism became increasingly important as people began to see themselves as citizens of a particular nation with a distinct national identity. Until the mid-19th century, relations between nation-states were dictated by treaty, agreements to behave in a certain way towards another state, unenforceable except by force, and not binding except as matters of honor and faithfulness. But treaties alone became increasingly toothless and wars became increasingly destructive, most markedly towards civilians, and civilized peoples decried their horrors, leading to calls for regulation of the acts of states, especially in times of war.

Perhaps the first instrument of modern public international law was the Lieber Code, passed in 1863 by the Congress of the United States, to govern the conduct of US forces during the United States Civil War and considered to be the first written recitation of the rules and articles of war, adhered to by all civilized nations, the precursor of public international law. Part of the Code follows:

"Military necessity, as understood by modern civilized nations, consists in the necessity of those measures which are indispensable for securing the ends of the war, and which are lawful according to the modern law and usages of war. Military necessity admits of all direct destruction of life or limb of armed enemies, and of other persons whose destruction is incidentally unavoidable in the armed contests of the war; it allows of the capturing of every armed enemy, and every enemy of importance to the hostile government, or of peculiar danger to the captor; it allows of all destruction of property, and obstruction of the ways and channels of traffic, travel, or communication, and of all withholding of sustenance or means of life from the enemy; of the appropriation of whatever an enemy's country affords necessary for the subsistence and safety of the Army, and of such deception as does not involve the breaking of good faith either positively pledged, regarding agreements entered into during the war, or supposed by the modern law of war to exist. (...But...) Men who take up arms against one another in public war do not cease on this account to be moral beings, responsible to one another and to God. Military necessity does not admit of cruelty—that is, the infliction of suffering for the sake of suffering or for revenge, nor of maiming or wounding except in fight, nor of torture to extort confessions. It does not admit of the use of poison in any way, nor of the wanton devastation of a district. It admits of deception, but disclaims acts of perfidy; and, in general, military necessity does not include any act of hostility which makes the return to peace unnecessarily difficult."

This first statement of the previously uncodified rules and articles of war led to the first prosecution for war crimes—in the case of United States prisoners of war held in cruel and depraved conditions at Andersonville, Georgia, in which the Confederate commandant of that camp was tried and hanged, the only Confederate soldier to be punished by death in the aftermath of the entire Civil War.

In the years that followed, other states subscribed to limitations of their conduct, and numerous other treaties and bodies were created to regulate the conduct of states towards one another in terms of these treaties, including, but not limited to, the Permanent Court of Arbitration in 1899; the Hague and Geneva Conventions, the first of which was passed in 1907; the International Court of Justice in 1921; the Genocide Convention; and the International Criminal Court, in the late 1990s. Because international law is a relatively new area of law its development and propriety in applicable areas are often subject to dispute.

Conflicts between public international law and national sovereignty

The conflict between international law and national sovereignty is subject to vigorous debate and dispute in academia, diplomacy, and politics. Certainly, there is a growing trend toward judging a state's domestic actions in the light of international law and standards. Numerous people now view the nation-state as the primary unit of international affairs, and believe that only states may choose to voluntarily enter into commitments under international law, and that they have the right to follow their own counsel when it comes to interpretation of their commitments. Certain scholars and political leaders feel that these modern developments endanger nation states by taking power away from state governments and ceding it to international bodies such as the U.N. and the World Bank, argue that international law has evolved to a point where it exists separately from the mere consent of states, and discern a legislative and judicial process to international law that parallels such processes within domestic law. This especially occurs when states violate or deviate from the expected standards of conduct adhered to by all civilized nations.

A number of states support very narrow interpretations of international law, including the People's Republic of China, the military junta currently holding power in Burma, and the Russian Federation. These states maintain that sovereignty—and thus what some view as the basis of sovereignty, the ultima ratio regum, or last argument of kings (force and coercion, by military or other means)—is the only true international law; thus seeing states as having free rein over their own affairs and their affairs in the larger world. Other states oppose this view. One group of opponents of this point of view, including many European nations, maintain that all civilized nations have certain norms of conduct expected of them, including the prohibition of genocide, slavery and the slave trade, wars of aggression, torture, and piracy, and that violation of these universal norms represents a crime, not only against the individual victims, but against humanity as a whole. States and individuals who subscribe to this view opine that, in the case of the individual responsible for violation of international law, he "is become, like the pirate and the slave trader before him, hostis humani generis, an enemy of all mankind, and thus subject to prosecution in a fair trial before any fundamentally just tribunal, through the exercise of universal jurisdiction. Another group believes that states only commit to international law with express consent, whether through treaty or customary law, and have the right to make their own interpretations of its meaning; and that international courts only function with the consent of states.

Though the European democracies tend to support broad, universalistic interpretations of international law, many other democracies have differing views on international law. Several democracies, including Israel, India, the United States, take a flexible, eclectic approach, recognizing aspects of public international law as universal, regarding other aspects as arising from treaty or custom, and viewing certain aspects as not being subjects of public international law at all. Democracies in the developing world, due to their past colonial histories, often insist on non-interference in their internal affairs, particularly regarding human rights standards or their peculiar institutions, but often strongly support international law at the bilateral and multilateral levels, such as in the United Nations, and especially regarding the use of force, disarmament obligations, and the terms of the UN Charter. Although considerable differences exist amongst democracies as to their policies and practices regarding international law, most dictatorships have very low regard for any kind of international law, either in principle, or in practice, except when it comes to the international laws that protect their own thrones and sovereignties; indeed, most grave breaches of public international law are committed by dictatorships.


Public international law has three primary sources: international treaties, custom, and general principles of law. International treaty law comprises obligations states expressly and voluntarily accept between themselves in treaties. Customary international law is derived from the consistent practice of States accompanied by opinio juris, i.e. the conviction of States that the consistent practice is required by a legal obligation. Judgments of international tribunals as well as scholarly works have traditionally been looked to as persuasive sources for custom in addition to direct evidence of state behavior (and they are also explicitly mentioned as such in Art. 38 of the Statute of the International Court of Justice, as subsidiary means for the determination of rules of law). Attempts to codify customary international law picked up momentum after the Second World War with the formation of the International Law Commission (ILC), under the aegis of the United Nations. Codified customary law is made the binding interpretation of the underlying custom by agreement through treaty. For states not party to such treaties, the work of the ILC may still be accepted as custom applying to those states. General principles of law are those commonly recognized by the major legal systems of the world. Certain norms of international law achieve the binding force of peremptory norms (jus cogens) as to include all states with no permissible derogations.


Where there are disputes about the exact meaning and application of national laws, it is the responsibility of the courts to decide what the law means. In international law as a whole, there are no courts which have the authority to do this. It is generally the responsibility of states to interpret the law for themselves. Unsurprisingly, this means that there is rarely agreement in cases of dispute. Insofar as treaties are concerned, the Vienna Convention on the Law of Treaties writes on the topic of interpretation that:
"A treaty shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose." (article 31(1))
This is actually a compromise between three different theories of interpretation:

  • The textual approach, a restrictive interpretation, which bases itself on the "ordinary meaning" of the text; that approach assigns considerable weight to the actual text.
  • The subjective approach, which takes into consideration i. the idea behind the treaty, ii. treaties "in their context", and iii. what the writers intended when they wrote the text.
  • A third approach, which bases itself on interpretation "in the light of its object and purpose", i.e. the interpretation that best suits the goal of the treaty, also called "effective interpretation".

These are general rules of interpretation; specific rules might exist in specific areas of international law.


Since international law exists in a legal environment without an overarching "sovereign" (i.e., an external power able and willing to compel compliance with international norms), "enforcement" of international law is very different than in the domestic context. In many cases, enforcement takes on Coasian characteristics, where the norm is self-enforcing. In other cases, defection from the norm can pose a real risk, particularly if the international environment is changing. When this happens, and if enough states (or enough powerful states) continually ignore a particular aspect of international law, the norm may actually change according to concepts of customary international law. For example, prior to World War I, unrestricted submarine warfare was considered a violation of international law and ostensibly the casus belli for the United States' declaration of war against Germany. By World War II, however, the practice was so widespread that during the Nuremberg trials, the charges against German Admiral Karl Dönitz for ordering unrestricted submarine warfare were dropped, notwithstanding that the activity constituted a clear violation of the Second London Naval Treaty of 1936.

Enforcement by states

Apart from a state's natural inclination to uphold certain norms, the force of international law has always come from the pressure that states put upon one another to behave consistently and to honor their obligations. As with any system of law, many violations of international law obligations are overlooked. If addressed, it is almost always purely through diplomacy and the consequences upon an offending state's reputation. Though violations may be common in fact, states try to avoid the appearance of having disregarded international obligations. States may also unilaterally adopt sanctions against one another such as the severance of economic or diplomatic ties, or through reciprocal action. In some cases, domestic courts may render judgment against a foreign state (the realm of private international law) for an injury, though this is a complicated area of law where international law intersects with domestic law.

It is implicit in the Westphalian system of nation-states, and explicitly recognized under Article 51 of the Charter of the United Nations, that all states have the inherent right to individual and collective self-defense if an armed attack occurs against them. Article 51 of the UN Charter guarantees the right of states to defend themselves until (and unless) the Security Council takes measures to keep the peace.

Enforcement by international bodies

Violations of the UN Charter by members of the United Nations may be raised by the aggrieved state in the General Assembly for debate. The General Assembly cannot make binding resolutions, only 'recommendations', but through its adoption of the "Uniting for Peace" resolution (A/RES/377 A), of 3 November1950, the Assembly declared that it has the power to authorize the use of force, under the terms of the UN Charter, in cases of breaches of the peace or acts of aggression, provided that the Security Council, owing to the negative vote of a permanent member, fails to act to address the situation. The Assembly also declared, by its adoption of resolution 377 A, that it could call for other collective measures—such as economic and diplomatic sanctions—in situations constituting the milder "threat to the Peace".

The Uniting for Peace resolution was initiated by the United States in 1950, shortly after the outbreak of the Korean War, as a means of circumventing possible future Soviet vetoes in the Security Council. The legal significance of the resolution is unclear, given that the General Assembly cannot issue binding resolutions. However, it was never argued by the "Joint Seven-Powers" that put forward the draft resolution, during the corresponding discussions, that it in any way afforded the Assembly new powers. Instead, they argued that the resolution simply declared what the Assembly's powers already were, according to the UN Charter, in the case of a dead-locked Security Council. The Soviet Union was the only permanent member of the Security Council to vote against the Charter interpretations that were made law by the Assembly's adoption of resolution 377 A.

Alleged violations of the Charter can also be raised by states in the Security Council. The Security Council could subsequently pass resolutions under Chapter VI of the UN Charter to recommend the "Pacific Resolution of Disputes." Such resolutions are not binding under international law, though they usually are expressive of the Council's convictions. In rare cases, the Security Council can adopt resolutions under Chapter VII of the UN Charter, related to "threats to Peace, Breaches of the Peace and Acts of Aggression," which are legally binding under international law, and can be followed up with economic sanctions, military action, and similar uses of force through the auspices of the United Nations.

It has been argued that resolutions passed outside of Chapter VII can also be binding; the legal basis for that is the Council's broad powers under Article 24(2), which states that "in discharging these duties (exercise of primary responsibility in international peace and security), it shall act in accordance with the Purposes and Principles of the United Nations". The mandatory nature of such resolutions was upheld by the International Court of Justice (ICJ) in its advisory opinion on Namibia. The binding nature of such resolutions can be deduced from an interpretation of their language and intent.

States can also, upon mutual consent, submit disputes for arbitration by the International Court of Justice, located in The Hague, Netherlands. The judgments given by the Court in these cases are binding, although it possesses no means to enforce its rulings. The Court may give an advisory opinion on any legal question at the request of whatever body may be authorized by or in accordance with the Charter of the United Nations to make such a request. Some of the advisory cases brought before the court have been controversial with respect to the court's competence and jurisdiction.

Often enormously complicated matters, ICJ cases (of which there have been less than 150 since the court was created from the Permanent Court of International Justice in 1945) can stretch on for years and generally involve thousands of pages of pleadings, evidence, and the world's leading specialist public international lawyers. As of 2005, there are twelve cases pending at the ICJ. Decisions made through other means of arbitration may be binding or non-binding depending on the nature of the arbitration agreement, whereas decisions resulting from contentious cases argued before the ICJ are always binding on the involved states.

Though states (or increasingly, international organizations) are usually the only ones with standing to address a violation of international law, some treaties, such as the International Covenant on Civil and Political Rights have an optional protocol that allows individuals who have had their rights violated by member states to petition the international Human Rights Committee.


Through the ages a code developed for the relations and conduct between nations. Even when nations were at war, envoys were often considered immune to violence. The first formal attempts in this direction, which over time have developed into the current international law, stem from the era of the Renaissance in Europe. In the Middle Ages, it had been considered the obligation of the Church to mediate in international disputes. During the Council of Constance (1414) Pawel Wlodkowic, rector of Jagiellonian University (Kraków, Poland), theologian, lawyer and diplomat, presented the theory that all, including pagan, nations have right to self-govern and to live in peace and possess their land.

At the beginning of the 17th century, several generalizations could be made about the political situation:

  1. Self-governing, autonomous states existed.
  2. Almost all of them were governed by monarchs.
    1. The Peace of Westphalia is often cited as being the birth of the modern nation-states, establishing states as sovereigns answering to no-one within their own borders.
  3. Land, wealth, and trading rights were often the topics of wars between states.

Some people assert that international law developed to deal with the new states arising, others claim that the lack of influence of the Pope and the Roman Catholic Church gave rise to the need for new generally-accepted codes in Europe.

The French monk Emeric Cruce (1590–1648) came up with the idea of having representatives of all countries meeting in one place to discuss their conflicts so as to avoid war and create more peace. He suggested this in his The New Cyneas (1623), choosing Venice to be the selected city for all of the representatives to meet, and suggested that the Pope should preside over the meeting. Of course, during the Thirty Years' War (1618–1648), this was not acceptable to the Protestant nations. He also said that armies should be abolished and called for a world court. Though his call to abolish armies was not taken seriously, Emeric Cruce does deserve his place in history through his foresight that international organizations are crucial to solve international disputes.

The statesmen of the time believed no nation could escape war, so they prepared for it. King Henry IV's Chief Minister, the Duke of Sully, proposed the founding of an alliance of the European nations that was to meet to arbitrate issues and wage war not between themselves but collectively on the Ottoman Turks, and he called it the Grand Design, but was never established.

After World War I, the nations of the world decided to form an international body. U.S. President Woodrow Wilson came up with the idea of a "League of Nations". However, because of political wrangling in the United States Congress, the United States did not join the League of Nations, which was one of the causes of its demise.

When World War II broke out, the League of Nations was finished. Yet at the same time, the United Nations was being formed. On January 1, 1942, U.S. President Franklin D. Roosevelt issued the "Declaration by United Nations" on behalf of 26 nations who had pledged to fight against the Axis powers. Even before the end of the war, representatives of 50 nations met in San Francisco to draw up the charter for an international body to replace the League of Nations. On October 24, 1945, the United Nations officially came into existence, setting a basis for much international law to follow.

Modern international law is often affirmed as the product of modern European civilization.

The seafaring principalities of India established legal rules for ocean navigation and regional commerce.

The Greek system of independent city-states bore a close resemblance to contemporary nation-state system. The Aetolian and Achaean leagues of the 3rd century BC represented early organisational efforts at international cooperation and facilitated the development of arbitration as a dispute settlement technique.

International legal theory

Natural law

The intellectual seeds of modern international law germinated in the 16th and 17th centuries, when the influence of the Roman Catholic Church in international affairs gradually weakened. Many early international legal theorists were concerned with axiomatic truths thought to be reposed in natural law. Among the early natural law writers, Francisco de Vitoria, Dominican professor of theology at the University of Salamanca, examined the question of just war and Spanish authority in the Americas. He did so while Spain was at the height of its power, after the violent Spanish conquest of Peru in 1536.

See also: Discrimination

Eclectic school

Central in the development of modern international law was Hugo Grotius a Dutch theologian, humanist and jurist. In his principal work De jure Belli ac Pacis Libri Tres ("Three Books on the Law of War and Peace"; 1625), Grotius claimed that nations as well as persons ought to be governed by universal principle based on morality and divine justice. Much of Grotius's content drew from the Bible and from classical history (just war theory of Augustine of Hippo). Drawing also from domestic contract law, he also noted that relations between polities were governed by jus gentium, the law of peoples, which had been established by the consent of the community of nations. (See pacta sunt servanda).

The fundamental facets of the Grotian or eclectic school, especially the doctrines of legal equality, territorial sovereignty, and independence of states, became definitive to international law in Europe. These principals were recognised in the Peace of Westphalia and became the foundation for the treaties of Osnabrück and Münster.

Another eclectic thinker, German philosopher Christian von Wolff, contended that the foundation for international community should come as a world superstate (civitas maxima), having authority over the component member states. This view was rejected by the Swiss diplomat Emmerich de Vattel, who favoured a rationale of equality of states as articulated by 18th century natural law. Vattel suggested in his major work Le droit des gens that the law of nations was composed of custom and law on the one hand, and natural law on the other.

Legal positivism

The early positive school emphasized the importance of custom and treaties as sources of international law. Among the early positivists was Alberico Gentilis, a professor of civil law at Oxford who used historical examples to posit that positive law (jus voluntarium) was determined by general consent. Another professor at Oxford, Richard Zouche, published the first manual of international law in 1650.

In the 18th century legal positivism became popular and found its way into international legal philosophy. The principal figure among 18th century positivists was Cornelius van Bynkershoek, a celebrated Dutch jurist who asserted that the bases of international law were customs and treaties commonly consented to by various states. A second positivist, John Jacob Moser was a prolific German scholar who emphasized the importance of state practice in international law. A contemporary German scholar, Georg Friedrich von Martens, published the first systematic manual on positive international law, Precis du droit des gens moderne de l'Europe.

The growth of nationalism and Hegelian philosophy in the 19th century pushed natural law farther from the legal realm. Commercial law became nationalized into private international law, distinct from public international law. Positivism narrowed the range of international practice that might qualify as law, favouring rationality to morality and ethics. The Congress of Vienna in 1815 marked formal recognition of the political and international legal system based on the conditions of Europe.

Branches of public international law



  • Brownlie, Ian (2003) Principles of Public International Law, Oxford University Press, 6th Ed., ISBN 0199260710
  • Lawson, Edward, and Mary Lou Bertucci, Encyclopedia of human rights , 2nd ed., Taylor & Francis, 1996
  • Osmanczyk, Edmund, The encyclopedia of the United Nations and international relations , Taylor & Francis, 1990
  • Shaw, Malcom N., International Law, 5th ed., Cambridge University Press, 2003

See also

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