Sources of International Law


International law does not have any codified form and is derived from various sources. International law deals with dispute between nations or between nationals of various states. Article 38 of Statute of the International Court of Justice, 1946 mentions five major sources of international law. Treaties, customs, general laws, judicial decisions and judicial writings forms such sources. This paper tries to provide a report of such sources in the order of importance.


Sources of International Law.. 1

1     Introduction. 4

2     Types of international law. 4

2.1      Public international law.. 4

2.2      Private international law.. 5

3     Sources of international law. 5

3.1      Treaties 6

3.1.1       Significance. 7

3.1.2       Contribution. 7

3.2      International customs 8

3.2.1       Significance. 8

3.2.2       Contribution. 9

3.3      General principles of law.. 10

3.3.1       Significance. 10

3.4      Judicial decisions and juristic writings. 10

3.4.1       Judicial decisions 11

3.4.2       Juristic writings 11

3.5      WTO and GATT. 12

3.6      Conclusion. 12

References 14

1       Introduction

International law is a sum of several rules and regulations applied in the act of regulation of international community. International law lacks any “Code” or parliament or any body that can be called as legislation. International Court of Justice (ICJ) is in a way considered as the court for settling disputes on international matters. Other than this there are several international courts and tribunals whose jurisdiction in international matters is dependent on parties consent. Hence such specialized tribunals and courts do not have compulsory jurisdiction opposed to national courts. Thus it can be seen that international law is decentralized in form and is to a great extent dependent on the actions of international community and this community is constituted by 192 states. In general we can say that International law is the body of rules and regulations governing relationship between states. This paper tries to outline and explain the main sources of international law and to evaluate them in terms of their significance and importance in promoting the growth and development of international business or trade (Schreuer, nd).

2       Types of international law

International law in its initial stage aimed to preserve peace among nations and at present it deals mainly with issues related to foreign policy, economic relationships and power balance. International law can be generally divided in to two branches private international law and public international law.

2.1.1      Public international law

Public international law is about the relation between states and its nationals. Public international law is codified under various matters of dispute like international trade, immigration, war conduct, criminal extradition, naturalization law, human rights and international aviation and admiralty laws.

2.1.2      Private international law

Private international laws are mostly referred to as conflict of laws because it deals with controversies in jurisdiction basically. At times a single matter will come under more than one jurisdiction and it is at this event that private international law is usually applied. It also deals with enforcement of foreign judgment. Private international law applies to corporations, individuals and other business entities and is also known as transnational law(Degan, 1997).

3       Sources of international law

International law does not have a single source as it is not codified under a single Act or regulation. It can be considered as an outcome of all the processes and materials applied for regulating and developing international community. These laws are influenced by various legal and political theories. Authority of a sovereign was considered to be limited to acts of consent to an agreement during 19th century and this was in accordance with the legal principle of pacta sunt servanda(agreements must be kept). This is the basic principle on which international laws are formed. Thus it is the consent of states that forms the cornerstone of international law. It is this consensual view that was reflected in Statute of the Permanent Court of International Justice formed in 1920. Same maxim can be seen to be preserved in Article 38 (1) of Statute of the International Court of Justice, 1946.

Article 38 (1) describes the laws that International Court of Justice need to apply while deciding cases that comes with in its jurisdiction and this article is considered as the most authoritative listing about international law sources. According to this article, international conventions, international customs, general principles of law, judicial decisions and “teachings of the most highly qualified publicists” are to be applied by International Court of Justice in deciding cases that comes with in its jurisdiction. Thus these five sources are considered as the most important sources of international law (Degan, 1997).

When there is a dispute regarding preference between sources treaties are to be considered over any other source if such an instrument is applicable to issue in question. There is an argument that international customs and treaties are of equal value in international law and this is under the view that a new custom is likely to supersede a treaty that was formed ling before or a new treaty is likely to supersede a custom that was formed earlier. Juristic writings and judicial decisions are considered as auxiliary sources. At the same time there is no clarity as to whether general principles of law that exists in civilized nations are to be considered as auxiliary source or principal source in international law.

There is a view that practice of international organizations like United Nations which is there in Security Council resolutions or resolutions of General Assembly are to be considered as a source of international law. There are situations when modification is likely to occur in a treaty as a result of practices that takes place between parties to treaty. At times a rule is also likely to take precedence over the provisions of treaty when such a rule is given special status as part of jus cogens (compelling law). Such laws are to be followed by nations strictly and will stand above any other laws national or international (Hoof, 1983).

3.1      Treaties

Most credible laws of international law are treaties and conventions and are they are hence considered as “hard law”. International law is based on the legal principle of pacta sunt servanda and treaties almost serve this purpose. They play the role of a contract between two or more countries. Examples of treaties are defense pact or extradition treaty. At times treaties are considered as a legislation that regulates internationals relations particular aspects and at times they act as constitutions of an international organization. All treaties form a kind of contract between countries that are parties to it and hence can be regarded as source of law. Through the word “international conventions” mentioned in Article 38 (1) (a) in the Statute of the International Court of Justice, 1946 aims at treaties. Along with that this provision is also acknowledging the possibility of countries accepting treaties expressly even if they are not parties to it formally. Any treaty to be considered as a source of law need to affect non parties or must have any consequence that is more extensive than the ones imposed specifically by that particular treaty (D’Amato, 1971).

3.2      Significance

Treaties are considered as the most important source of international law. This is due to the fact that in treaty there is a contractual obligation between parties and this is almost like a legal practice that is to be followed. Further certain treaties are formed by codifying customary laws that are in existence, for example jus ad bellum and laws governing global commons. The purpose of formation of such treaty is to make a code that is generally applicable. Some treaties acquire international acceptance due to ratification by large number of states example Geneva Conventions for the Protection of War Victims, 1949. Such treaties are considered as international law in its own right.

3.3      Contribution

One of the major contributions made by treaties in international law is the importance that it granted to human rights. Human rights are considered as the most important right globally and this is the result of treaties formed for protecting human rights. Treaties are always legally binding on parties and are to be carries out in same manner as a contract. Treaties have contributed largely to various areas of international law and even to most recent subjects like usage of nuclear weapons, law relating to space etc. It was after World War II that most treaties came in to existence and focus of majority of them was on human rights. Thus it is through treaties that international law gained humanitarian aspect in all its dealings. Most treaties are meant to reproduce customary law in an international scenario and the best example for this is Vienna Convention on the Law of Treaties, 1969 (Thirlway, 1972). At the same time some treaties are in turn adopted by countries as customary rules (Nicaragua v United States of America [1986] ICJ Reports 14).

3.4      International customs

Though custom is referred to as a main source of international law, for that to be considered as international law there need to have one specific emphasis plus opinio juris sive necessitatis or acceptance of such practice as obligatory. Firstly such a practice must be consistent in states and states need to certain that such practice is necessary as a legal obligation. At times even comity has been considered as international law for example diplomatic immunity. Customary international law is different from this with the presence of opinio juris (United Kingdom v Iceland [1974] ICJ Reports 3). Most customary international laws have been replaced by treaties.

3.5      Significance

Most treaties aim to give international acclaim to customary laws and thus it can be seen that customary laws has contributed largely to international law. For a customary practice is considered as international law according to occasion or when the statement is made (Federal Republic of Germany v Denmark; Federal Republic of Germany v Netherlands [1969] ICJ Reports 4). In some situations such a statement of a state is merely considered as a conduct that is necessary in a specific situation. When such a practice is regular, consistent, common and concordant it is considered as law internationally (Colombia v Peru [1950] ICJ Rep 266). All states that are affected by such a practice need to have participation in sufficient degree (Portugal v India [1960] ICJ Reports 6) and any substantial dissent must not be present (Federal Republic of Germany v Denmark; Federal Republic of Germany v Netherlands) [1969] ICJ Reports 4). International Court of Justice has rejected the existence of customary practices in the absence of consistency of practice. If state accepts the rule as applicable, then also it becomes a law (United Kingdom v Norway [1951] ICJ Reports 116). Concept of instant custom is accepted by International Court of Justice and time constrained is not accepted as a bar (Libyan Arab Jamahiriya v Malta [1985] ICJ Reports 13).

3.5.1      Contribution

International customs have brought the aspect of opinion juris to international law as a necessary condition and it can not be presumed. Even if some acts lacks opinio juris they are considered as customary international law example usage of nuclear weapons, though it was not used after 1945. Another important factor is jus cogens (compelling law) and this is considered as an important factor to override other sources of international law. Importance of this concept is mentioned in Article 53 of Vienna Convention on the Law of Treaties. According to that

“For the purposes of the present Convention, a peremptory norm of general international law is a norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character”.

Customs have helped to bring common practices with legal acceptance to international law and thus made international law simple and acceptable to all.

3.6      General principles of law

Though Article (1) of the Statute of International Court of Justice has not mentioned the scope of this and there is controversy in this regard, it is considered that those principles that are applicable to several countries are to be considered as international law. If there is any limit or gap in any other source of international law Court can make use of general principles of law to fill that gap and thus prevent any non liquet. But not all general principles of law are considered as international law. It is necessary that such law has a relation with international officials or organizations employing them (Amerasinghe, 1994).

3.6.1      Significance

With increased number of treaties and conventions importance of general principles of law have reduced to a great extent. But certain concepts like equity and estoppel (Cambodia v Thailand [1962] ICJ Reports 6) are employed in international dispute adjudication. According to International Court of Justice “[o]ne of the basic principles governing the creation and performance of legal obligations” (Australia v France; New Zealand v France [1974] ICJ Reports 253) is the principle of good faith. Equity is also referred by the court as a necessity frequently (Netherlands v Belgium PCIJ Reports Series A/B No 70 76 at 76). It is said that legal rules cannot be subverted by using equity and this means that equity can not operate as contra legem (Burkina Faso v Republic of Mali [1986] ICJ Reports 554). United Nations Convention on the Law of the Sea, 1982 reinforces the perception of equity as law but it is the discretion of adjudicator basically. General rules of laws are to be considered as a source of inspiration rather than law itself to be applied directly (International Status of South-West Africa, 1950).

3.7       Judicial decisions and juristic writings

Article 38(1) (d) of the Statute of International Court of Justice states that

“Judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law”.

It is not easy to describe the influence these materials posses for international law’s development. But it is to be notes that most pleadings before International Court of Justice are stuffed with legal literature and case laws.

3.7.1      Judicial decisions

Decisions of municipal and international courts and academic papers are not to be considered as law as such or its source, but they are to be used as means for recognizing various laws that are established in various other sources. Though International Court of Justice invokes its previous rulings and judgments it does not refer to decisions made by domestic courts. This is because in international law there is no stare devises rule. A decision made by International Court of Justice is binding only on parties and it is only with respect to that particular case that such a decision is binding (Statute of the International Court of Justice, 1946). But court often refers to its past decision to support and explain its present case. Resolutions of General Assembly are often considered by International Court of Justice as an analytic of customary international law.

3.7.2      Juristic writings

According to Article 38(1) (d) of the Statute of International Court of Justice

“Teachings of the most highly qualified publicists of the various nations are subsidiary means for the determination of the rules of law”.

Though scholarly papers of prominent jurists are not considered as international law sources theya re necessary for developing rules of treaties, general principles of law and customs. This is why such works are also mentioned as source of international law. Such papers are often used for interpreting international law and same method was made use of by Supreme Court of United States in the case of Paquete Habana [175 US (1900) 677 at 700-1].

3.8        WTO and GATT

WTO and GATT have very significant roles to play in international laws. It was with the formation and development of World Trace Organization in 1995 that fair trading practices became important in trade between countries. WTO does not have specific rules governing trade among nations, but such rules are found in treaties that are annexed to Marrakesh Agreement. Thus WTO provides specific framework for administration and implementation of trade agreements. It also creates a form for negotiation, facilitates review mechanism for trade policies and at the same promote among members greater coherence in economic policies. WHO envisages the principles of non discrimination, market access, balancing of trade liberalization along with other social interests and national regulations harmonization through agreements like TBT, SPS and TRIPS? GATT at the same time deals with issues of subsidies and dumping rules of unfair trade practices. Thus WTO along with GATT have made trade between nations a fair activity and thus contributed to international law (van den Bossche, 2008).

4       Conclusion

International law is not a law drafted and adopted by international community. It is derived from various sources like treaties customary laws, general principles of law, judicial decisions and writings WTO and GATT. Several matters ranging from human rights to fair trade and nuclear weapons are considered in this and every new treaty signed by countries make new contribution to international law. It is through these sources that such vast area of dealings is covered in international law. It is not possible to draft laws in all areas that are likely to affect international community and hence the only possible and successful method is to adopt laws from these sources. As relation between countries is mostly set through treaties, they are considered as most important source. At the same time most treaties are extension of customary laws and thus customary laws also plays significant role in development and growth of international law. As trade is the most important issue dealt by international law any new treaty or rule adopted by GATT or WTO will also form a source for international law with regard to practices of trade.


Amerasinghe, C (1994) The Law of the International Civil Service. Oxford: Clarendon Press

Australia v France; New Zealand v France [1974] ICJ Reports 253

Burkina Faso v Republic of Mali [1986] ICJ Reports 554

Cambodia v Thailand [1962] ICJ Reports 6

Colombia v Peru [1950] ICJ Rep 266

D’Amato, A (1971) The Concept of Custom in International Law. New York: Cornell University Press

Degan, V, D (1997) Sources of International Law. Netherlands: Kluwer Law International.

Federal Republic of Germany v Denmark; Federal Republic of Germany v Netherlands) [1969] ICJ Reports 4

Hoof, G, J, H (1983) Rethinking Sources International Law. Hingham: Kluwer Academic publishers

International Status of South-West Africa (Advisory Opinion) [1950] ICJ Reports 128

Libyan Arab Jamahiriya v Malta [1985] ICJ Reports 13

Netherlands v Belgium PCIJ Reports Series A/B No 70 76 at 76

Nicaragua v United States of America [1986] ICJ Reports 14

Portugal v India [1960] ICJ Reports 6

Schreuer, C (nd) Sources of International Law: Scope and Application. [Online] Available at: Accessed on February 22nd 2013.

Statute of the International Court of Justice, 1946

Thirlway, H (1972) International Customary Law and its Codification. Leiden: A. W. Sijthoff

United Kingdom v Iceland [1974] ICJ Reports 3

United Kingdom v Norway [1951] ICJ Reports 116

Van den Bossche, P (2008). The Law and Policy of the World Trade Organization – Text, Cases and Materials. Maastricht University: Cambridge University Press.