Sources of International Law

The sources of international law refer to those methods and elements from which the rules of international law are derived.
According to Stark, by the source of international law we mean the actual material that international jurists use to formulate the rules of international disputes.
According to Edward Collins, by the sources of international law we mean the methods and process by which international law is born.
The sources of international law can be divided into the following categories-

International convention,
International Customs,
General Principles of law recognized by civilized states,
Decisions of Judicial or Arbitral Tribunals
Works of jurists and commentators
Decisions of organs of international organizations

Sources developed in the twentieth century – General principles of law developed by civilized states and decisions of organs of international organizations.

There are no codified rules relating to the sources of international law, so in the absence of codified rules the Covenant under Article 38 of the Statute of the International Court of Justice has an important place in relation to the sources of international law.

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Sources mentioned in Article 38 of the Statute of the International Court of Justice-

International Convention
International Customs
General Principles of law recognized by civilized states
Secondary sources of international law – judicial decisions and works of highly qualified judges and commentators.

International Convention

In modern times, the first and most important source of international law is ‘International Convention’. The term ‘International Convention’ includes all types of international treaties.

According to the definition of treaty given in section (2) of the Vienna Convention 1969, “International treaties are those agreements by which two or more states establish relations among themselves under international law.”
There are two types of international treaties-

law making treaties
Treaty contracts

1 Law-making Treaties –

The provisions of law-making treaties are the direct sources of international law. The main reason for the rapid development of the provisions of law-making treaties is the custom(practice) proving inappropriate to changing circumstances.
Law making treaties can be classified into two parts-

Treaties that create universal international law. The best example of this type of treaty is the United Nations Charter.
Those treaties which create general principles of international law. These treaties are agreements of a large number of states which propound the general principles of international law. Their main examples are-

Treaty of Versailles, 1919
Geneva Convention, 1929
Covenant of the League of Nations, 1919
Charter of the United Nations, 1945
Vienna Convention on the Law of Treaties, 1998
Geneva Conventions on the Law of the Sea, 1960
Hague Convention, 1899, 1900
Treaty of Westfalia, 1948 etc.

In fact, law-making treaties perform the same function in the international arena as legislation does in the field of state law. In the international arena, law-making treaties are the only means by which international law can be adapted to new circumstances. And the rule of law among the states can be strengthened.

According to Prof. Lyonas, “The treaty process is a good and useful means of universalizing international law.” But any treaty can enunciate a universal principle only if it has the support of the necessary states.

2. Treaty – Contracts –

Treaty – Contracts are made between two or more states and their provisions apply only to those states that are parties to them.

There are many reasons for international treaty being the main source: It clearly expresses the agreement of states, hence in modern times it has the unique qualities of giving birth to rules of international law, developing them, amending them etc.
Inspired by these reasons, Friedman has written that “in the fast-paced and international society today, instead of custom, international treaty has taken the place of main source.”

International Customs

The oldest source of international law is international customs. The provisions relating to international custom are set out in Article 38 (1) (b) of the Statute of the International Court of Justice. Customary rules of international law are those which have developed through a long historical process.

According to Starke, “The initial state of custom is usage; where usage ends, custom begins”

When states always behave in the same way in certain circumstances in their international relations, it is expected that they will behave in similar circumstances in the same way in the future too. This situation is called a usage. When there is general acceptance of the states regarding the above mentioned type of behavior, then it is believed that this type of behavior has become the right and responsibility of the states. Then the same practice takes the form of a custom.

According to Wiener, “custom is a practice which has acquired the power of law.”
Custom is the original and oldest source of international law and was at one time the most important of the sources. This was because the greater part of international law was made up of customary rules.
According to Oppenheim, “A custom is a clear and unchangeable disposition to perform certain acts, which has developed under the assumption that such acts are binding under international law.”
Customary rules refer to those rules which have been put into practice by most of the states for centuries as a matter of conduct.
According to Westlake, “customs are patterns of conduct that are agreed upon by society as binding.”
The development of customary international law has occurred due to three types of special circumstances

Diplomatic relations between states
Behavior of organs of international organizations
State laws, decisions of state courts, and military and administrative actions of states.

The main reason for the development of custom in international law is the lack of a powerful legislative institution.

In the North sea continental shelf cases – the Court not only acknowledged the relationship between treaty and custom but also made it clear that ratifying two or more international treaties is an important step in the development of custom.

Also revealed that at present, customs can also be created by treaties. For example, the first three articles of the Continental Geneva Convention 1958 are of the nature of creating rules.

In this case, the existence of similar rules in international treaty law and customary law was clearly recognized by the court.

West Randcentral Gold Mining Company Limited V.R. – The criterion regarding general acceptance or recognition of the practice is found in this case.

Right to Passage over Indian Territory cases of Purtgal v. India – In this case the International Court of Justice in India decided that if a particular behavior or habit between two states is considered equal to the law by both states, then it will be considered a binding custom between the two states.

The case of Paguete Habana is an example of the judicial application of custom. In this case, it has been decided that if there is no treaty on any subject, nor any law of the executive or legislature, nor any judicial decision, then the court, to know the international law, will look at the customs and behavior of civilized states and as evidence of these, will look at the writings of jurists and commentators who have familiarized themselves with those subjects through years of labour, research and experience.

In the Asylum case – the International Court of Justice said about diplomatic relations that “the parties who rely on custom must prove that the rule they are presenting as evidence is a rule followed in uniform and consistently by the States.”

In the Fisheries Case- The International Court of Justice refused to accept the existence of the 10-mile rule for the Gulf.

Customary rules of international law can be either universal or specific.
Universal customary rules are rules that are universally binding on all states in the same way as the fundamental rules of diplomatic relations or treaty law of the sea.
Specific customary rules or local customary rules are rules that are binding on states.
The principle of specific customary rules is based on the wording of Article 38 (1) (b) of the Statute of the International Court of Justice,

In Morocco case – The International Court of Justice first used the term “local custom” in a case involving United States citizens.

In Case of Right of Passage over Indian territory Specific or local customs were recognized in 1960.

Elements of custom

Like state law, in international law too, a custom is considered binding only when the following characteristics or elements are present in it :

The custom must have been prevalent for a long time.
The custom must be reasonable.
There should be a custom that is followed consistently.
There should be uniformity.
It is mandatory to follow this
States commonly practice this

An essential element of a custom is that it should be certain. If there is any uncertainty, ambiguity about it then the custom will lose its significance.
The observance of the custom must be mandatory. If its observance is voluntary then the custom has no binding effect.
As a result of the increasing pace of change in the international community, custom is considered an inappropriate instrument for bringing about change in international law and developing new rules.
According to Professor Lyonas, “The development of custom happens very slowly and instead of that, changes can be made quickly by treaty and the law can be made suitable to the time and circumstances.” The decision of SS Lotus case is no longer valid in the present time.

Continental Shelf Cases are an example of a rapidly evolving practice in the present times.

General principles of law recognised by civilized states

The general principles of law recognised by civilized states have been placed third in Article 38. General principles of law recognised by civilized states mean those rules which have been recognized by almost all civilized states.

The International Court of Justice will apply the general principles of law recognized by civilized nations when there is no treaty relevant to the dispute or when there is no customary international law which can be applied to the particular case.

The general principles of law recognized by civilized states mean those principles which are used by most or all the states of the world community in the regulation of national law and due to their development, they can also be used in international law.

Recognized general principles are included in the sources of international law because they have been found to be generally recognised by civilized legal systems and can be used to maintain justice in any system. Recognition by civilized states General principles of accepted law do not automatically become principles of international law, rather these rules must be approved by the World Court.

According to Lord McNair, Article 38(1)(c) of the Statute of the International Court of Justice provides an inexhaustible source of legal principles from which the Court may draw help and can develop public international Law.

According to Facett, “The rules or standards of the general principle of law are those which are repeatedly repeated in the practice of developed systems of law either because they have a common origin, such as Roman law, or because they are common to the basic needs of human community.”

According to Justice Chagla, In Case of Right of Passage over Indian Territory Case- “A principle of international law can be adopted from state law if it is universally accepted and is not inconsistent with any rule of international law.”

The general rules of law accepted by civilized states also include the principles of procedure and evidence, provided they are recognized by the nations by giving them general acceptance.

The general principles of law recognised by civilized states have attacked positivism.

Examples of the general principles of law reognised by civilized states –

Pacta Sunt Servanda
Reparation for Injuries
Right of self defense
No person can be a judge in his own case.
The person making the decision must listen to both sides.
Rules of equity, estoppel or obstruction
Harmony, Responsibility and Perpetual Rights
The right of each court to determine its own jurisdiction.
No question which has been validly and finally decided can be raised again between the same parties.

Major issues relating to general principles of law accepted by civilized nations.
In the case of Reg v. Keyn – It is expressed that international law is based on the logic of justice, equity, convenience and related matters which have been learned over a long period of time.
According to U.S.V. Schootner, ‘International law should be based on the rights of individuals and general principles of justice.

The general principle of estoppel was applied in the Diversion of Water from Meuse case by (PICJ) and ) in the Barcelona Traction case and the Temple of Preah Bihar case by (ICJ).
The Permanent Court of International Justice (PICJ) applied the principle of “prejudice” in the Diversion of Water from Meuse case and the Korzo Factory case. Similarly, the International Court of Justice (ICJ) applied the principle of prejudice in the Karfa Channel case.
International Court applies general principle of subrogation in Mavromotis Palestine waiver case

Decisions of Judicials or Arbitral Tribunals

Court decisions can be divided into two categories-

International judicial decisions,
Judicial Decisions of states

International judicial decisions,

In the modern era, the main international court of justice is – International Court of Justice (ICJ). The decision of the International Court of Justice is binding on the parties only in the case concerned. A previous decision of the International Court is not binding on the Court. The advisory opinion of the Court does not have binding effect. The decision of the International Court of Justice expresses the appropriate international law on a particular case. Judicial decisions are only a secondary source for determining the rules of Law .

Awards of international tribunals are not judicial but are merely quasi-judicial agreements and hence are not considered sources of international law.

In the case of German Interests in Police Upper Silesia, the PICJ clarified Article 59, saying that the purpose of Article 59 is generally not to make the legal principles accepted by the Court in specific cases binding on other parties or in other disputes.

Judicial Decisions of States (Decisions of the municipal court)

Decisions of the courts of states can take the form of rules of international law in two ways.

Decisions of the courts of states are considered as weighty and important precedents. According to Chief Justice Marshall, “The decisions of the courts of each country show how international law is understood and applied in that country in those circumstances”.
Decisions of the courts of states can become rules of international custom under the same rules and circumstances in which the custom develops. The decisions of the courts are a secondary source of determining the law.

Openhiem did not consider the national court’s decision as a source of international law.

Works of jurists and commentators

The works of jurists and commentators are not considered independent sources of international law. Sometimes they are helpful in the development of international law. On their basis, international law is developed. The works of jurists and commentators are secondary sources of law.

In Case of Paquette habana– Judge Grey held , If there is no treaty or any executive or legislative decision on a matter, the court can resort to the customs of civilized states and the writings of jurists and commentators to determine what the law actually is on a matter.

The documents of competent jurists have been cited by the Court in many of its decisions – for example, the documents of jurists like Grotius, Vattel and Bynker Shoyak etc. have been cited by the International Court of Justice and International Tribunal. Many rules of international law have been created on the basis of the documents of jurists. Examples of such rules in international law are the Calvo Clause and the Drago Doctrine.
The writings of competent jurists are regarded as the last resort among the sources of international statute, so the Court will resort to them only when all other sources have failed to settle the dispute.

Decisions of organs of international organizations

According to Stark, the organs of international organizations develop international law in the following ways:

In their constitutional cases such decisions are secondary or final steps in the development of rules of custom.
The resolutions of the organs of these institutions and the rules or principles propounded for their work have a binding effect on the members of these institutions.
The organs of international organizations themselves decide what their capacity or capability will be.
Sometimes the organs of these institutions interpret different provisions of their constitutional documents.
And their nature is also binding. Thus their decisions are considered a part of the law of international organizations.
Organs of some international organizations have the right to give general semi-legislative or semi-judicial decisions.
In some special cases and circumstances, the organs of international organizations hand over such cases to jurists to know the law on the concerned matter. The opinions of these jurists are considered very important and it is very important in the development of the customary rules of international law. are
The decisions of the organs of international organizations are not mentioned in Article 38, the most appropriate reason for this is that this source has not been adequately developed by that time.

The decisions of organs of international organizations influence the sources of international law in the following ways:

International organizations are now considered international persons themselves. Therefore, they can develop practices or behaviors that take on the form of law or contribute to its development.
International organizations can develop legal rules to regulate the internal affairs of their organization.
States have begun to develop certain techniques and procedures to enable these organizations to adopt instruments that are legally binding on all or some of the members.
- The Treaty established by the European Economic Community (1957) is the best example of this, in which the rules made are directly binding on all member states.
International institutions provide a common forum for collective action by states, which is similar to permanent international conventions.
International organizations help in the development of international law by making multilateral treaties. These treaties are adopted in universal conferences and they contribute to the codification and gradual development of international law.

Other Sources

Ex aequo et bono

There is a provision of Ex aequo et bone in Article 38(2) of the Statute of the Court. According to this article, if the State Party gives its consent, then the Court can give a decision on the basis of Ex aequo et bone in addition to the appropriate sources. According to this provision It is not necessary for the court to decide the case according to law.

Subsidiary Sources

1.International Courtesy
Courtesy is based on the mutual behavior of nations. Courtesy means that when one nation behaves courteously with another nation, the other nation also has to treat it in the same way. According to Oppenheim, international courtesy has also formed the basis of international law.

2. Letters of States: In the early-modern era, almost all civilized nations have diplomatic relations with each other. States also correspond with each other on international topics, which states often adopt in their mutual relations.
According to Lawrence, often serious and complex questions of law are solved by the study of these state papers.

3. Instructions sent by the State to its officers
Legal advisors of governments advise the government to solve difficult problems on such questions which help in resolving difficult and controversial international cases, thus they also become sources of international law.

4. Logic
When there are no universally accepted rules in the matter of international law, then in that case such cases are settled by logic only. As a source of international law, logic means judicial logic. According to Pollock, “International law is based on the logic of justice, equity, convenience and object.”

5. Equity and justice

In the BarcelonaTraction case, Justice Fitz-Maris expressed the view that there is a need for rules and principles of equity and justice in the field of international law. These rules and principles can be given more attention at the present time.
In the North Sea Continental Case, the Court has mentioned 3 areas of equity and applicability – as follows-

Practice of states in international relations
International customary law
Administration of justice

The views expressed by Justice Angelotti and Justice Hudson in their dissenting opinions in the case of Diversion of Water from the Meuse were – “The principle of equity is so just, equitable and universally recognized that it should be applied in international relations.
The equitable principle was accepted by the Court in the Gulf of Maine Woundry case, the Continental Shelf case, Frontier Dispute Workina case.

At present, the principles of equity and justice are cited in the context of the new international economy and the creation of a new maritime law.

The order of use of sources of international law is given in Article 38 of the Court –
These are the following-
1. International Conventions
2. International Customs
3. General principles of law accepted by all nations
4. Court decisions and Works of jurists and commentators

References – Book

Dr. S.K. Kapoor, Human Rights & International Law, Central Law Agency.

International Law