This article is written by Shivani Panda, from Amity Law School, Delhi. This article explains the different sources of international law along with various case laws in detail.  

Introduction

The term ‘sources’ is very vague. Many scholars and jurists opined differently as to what is the meaning of the word ‘sources’ and what can be termed as actual and valid sources. Lassa Oppenheim, a renowned jurist whose work was mainly focused on analysing international law, observed in his book ‘International Law, a Treatise’, that sources of law is the name for a historical fact out of which rules of conduct came into existence. International law is comparatively a new branch of law. It has two sources: conventional and modern. However, since international law is dynamic and ever-changing, the list is open-ended. Many new sources have emerged with time. In this article, the author will discuss both the kinds of sources of law in detail and draw the connection between them.

Conventional sources

The conventional sources of international law are enumerated under Article 38(1) of the Statute of the International Court of Justice. These sources can be classified as ‘formal’ or ‘material’. Treaties, custom, and general principles are formal sources. They are obligatory in nature and legally binding on the parties who are involved in their constitution. Therefore, they are also known as hard laws. Material sources, on the other hand, are the interpretation of those obligatory rules. They involve judicial decisions and juristic teachings. However, with the evolution of international law, the accuracy of these sources are now in question. The conventional sources are further explained below in detail. 

• International conventions and treaties

Article 38(1)(a) of the Statute provides convention as one of the formal sources of international law. It states that, while deciding any case, the court shall apply general or particular international treaties that are expressly recognized by the contracting party. They are a binding written agreement between two or more parties, creating mutual rights and obligations. Thus, a treaty or convention is contractual in nature.  They are also known as a pact, agreement, covenant, charter, and memorandum of understanding.

• Kinds 

For a treaty to be a source of law and not just a source of obligation, it shall be universal and affect even the non-parties of the contract. Accordingly, treaties are divided into two types, that are as follows:

1. Law-making treaties: These kinds of agreements have a large number of parties. Thus, they are also called multilateral treaties. They can be used directly as a source of international law. Further, these treaties have a general legal standing, rather than being specific to the parties in a contract. They may lay down general rules or enunciate universal rules. Some examples of multilateral treaties are the United Nations Charter , Vienna Convention on the Law of Treaties, 1969 (VCLT), etc.
2. Treaty contracts: Treaty contracts or bilateral treaties are generally contracted between two parties. They are drafted in a way that they only suit the object, and establish the rights and obligations against the parties in the contract. Further, a treaty which is originally between two States can later be converted into a multilateral treaty by adding more parties that will be universally accepted by all. The Simla Agreement of 1972 between India and Pakistan is an example of a bilateral agreement. 

• Validity

The validity of the treaties or conventions is founded upon the maxim, Pacta Sunt Servanda, which means promises once made shall be kept. It is one of the oldest principles of international law. A treaty is not valid if it is not executed in good faith. The signatories of the agreement, in the absence of any provision, shall act in good faith. It is a governing principle of any convention, without which the contract is void. Further, it is enshrined in Article 2(2) of the UN Charter as well. The doctrine is also included in the General Principles of International Law. However, it is not an absolute principle, and there are a few exceptions to this rule. This principle is not binding on the State that emerged from an existing State, that is a part of the treaty. It is an exception to the rule of Rebus Sic Stantibus, which is explained in detail in the subsequent section of the article.

• Formation or conclusion of treaties

Treaties are generally between the head of the States however, a few agreements addressing minor issues can be between government departments. There is no codified procedure regarding the formation or conclusion of an international treaty. Nonetheless, there are a few steps given under VCLT that are to be followed while forming any convention. 

• Accrediting of representatives

Each State appoints a representative with the necessary authority to conduct negotiations and conclude treaties. They are given formal instruments by the head of the State or by the Ministry of Foreign Affairs namely, ‘full powers.’ It provides the person the authority to negotiate and adopt the covenant. Article 7 of the Vienna Convention regulates this procedure.

• Negotiation and adoption

Negotiation is conducted in a multilateral treaty through, ‘diplomatic conference’, and in a bilateral agreement through ‘discussions’. All the accredited persons shall present their proposals in the conferences, which are either accepted or rejected, and counter proposals are made. The final proposals approved by all the parties is called a draft treaty. According to Article 9 of the Vienna Convention, the draft treaty shall be adopted with the consent of all the participating parties and by the vote of two-thirds of the States present at the conference or by any other rule decided by the parties.

• Expression of consent

The VCLT provides several modes of expressing consent to become a party to a treaty. The agreement might expressly state the method of granting a consent or, it might be silent. When it is silent, either of the modes can be adopted by the parties.

1. Signature: A State can grant consent through the signature of its representative or accreditor. In practice, the signature is not considered as the final phase of demonstrating consent, and ratification of the treaty in the State is mandatory. 
2. Ratification: A ratification is a final form of expression of consent, after which the State is bound by a treaty. Very few Constitutions give the power to directly ratify the convention to the Parliaments. In most cases, approval from Parliament is required before it is ratified and applied to the Constitution. VCLT does not assign any time limit to ratify the treaty however, it shall be executed in a ‘reasonable time.’
3. Accession: In certain circumstances, a State may become a party to the treaty, in which it has neither participated in negotiations nor is a signatory. It has the same legal effect as ratification. 

• Entry into force

A treaty will have a binding effect on a State when it enters into force according to the provision of the contract. A multilateral covenant normally comes into force when a stipulated number of ratifications or accessions is received.

• Registration and publication

According to Article 102 of the UN Charter, every international agreement has to be registered with the Secretary-General of the United Nations. 

• Reservation, declarations, and derogations

1. A State often ratifies an agreement with the condition that it shall not be bound to specific provisions, which it expressly states in the treaty itself, or by an agreement between the contracting parties, or by a reservation made regarding those provisions. Reservation is defined under Article 2(1) of the Vienna Conventions. For example, reservation to the Genocide Convention was made by various countries. The reservations or unilateral declarations are binding, however whether they are a part of treaty, custom, or an independent source of international, is still debatable. 
2. Declaration slightly differs from reservations, as it does not affect any legal obligations mentioned in the treaty. It merely clarifies the State’s position regarding a provision. It is given at the time of signature, which then is annexed to the treaty.
3. Lastly, derogations are applied to the International Human Rights Law, which allows a State to temporarily suspend the exercise of certain treaties or conventions during armed conflict or national emergency.

• Invalidity

Article 42 of the Vienna Convention talks about the invalidity of treaties. It is analogous to that of the invalidity of a contract. The article states that a treaty can only be invalidated according to the grounds enumerated under this convention. Articles 46-53 stipulate various grounds, that are as follows: 

1. Lack of proper authority to represent the State
2. A mistake in the treaty
3. Coercion of the State and/or representative
4. Corruption of the representative
5. Jus Cogens

• Termination

Termination of a treaty means when a treaty ceases to exist or ends. It can still exist after its termination however, it will not be binding on the parties who defected from it. According to Part IV of the Vienna Convention treaties can be terminated by: 

1. Consent
2. A subsequent agreement 
3. Denunciation, that is, when a time-bound treaty comes to an end.
4. Material breach
5. Jus Cogens
6. Rebus Sic Stantibus

• Rebus Sic Stantibus

The principle of Rebus Sic Stantibus provides that when there has been a fundamental change in the circumstances since the enactment of a treaty or convention, a party can withdraw or terminate the agreement. The object of this doctrine is that sometimes due to some significant changes in a State, drastic measures have to be adopted that might be restricted under the treaty. Article 62 of the Vienna Treaty captures the essence of the doctrine. According to the Article, ‘fundamental change of circumstances’ cannot be invoked as a ground for terminating from a treaty in the following cases: 

1. If the treaty establishes a boundary
2. If the fundamental change is due to a breach by the party acting in contravention of the agreement against another party of the same treaty or of any other State.

• Customary international law

Custom is known as one of the oldest sources of international law. Before the emergence of treaties, customs were the sole source of international law. In fact, various conventions are the product of customs that have evolved with the changing needs of society. International custom is encapsulated under Article 38(1)(b) of the Statute of the International Court of Justice. It is regarded as the general practice accepted by law. However, it is difficult to establish the existence of an international custom in the court of law. That is the reason why the importance of custom has declined over time, and treaties and UN charters have replaced them.

• Meaning of custom

Custom is a habitual or accustomed course of conduct. In a primitive society, when the laws were not codified, rules of approved behaviour were laid down. They were assumed to be accepted by every person in the community by birth. As the society became complex, it became pertinent to lay down a few rules that were recognized as the right rule of conduct. The practices that got legal backing in the international plane are now known as the international custom laws. The ICJ in the Asylum Case described custom as, “a constant and uniform usage accepted as law.”

• Difference between custom and usage

Usage can be understood as behaviour that may be executed as a courtesy. Unlike custom, a person does not have any legal obligation to comply with the usages. According to J.G. Starke, an expert on international law remarked in his famous book, ‘Introduction to International Law’, that usage is the prior stage of custom. Custom begins when usage ends. It is the kind of rule that does not have any legal backing as of yet. Moreover, many usages do not require any legal attestation as its non-compliance does not lead to any dire consequences. They are done merely as social consciousness.

• Tests of an international custom

The existence of customary rules can be gathered from the practice and behaviour of the States. However, it is difficult to distinguish whether the rule adopted by the State was a custom or usage. Thus, Starke laid down two tests that should be conducted before giving any State rule legal attestation in the international platform.

• Material test 

The material test refers to the practice of the State. It is the objective element of the custom that is key to the establishment of a customary rule. It should be uniformly accepted by the citizens of the state. The duration and frequency of the practice should also be taken into account before announcing it as customary international law.

• Psychological test

This test comes into being when the material test is unambiguous. The subjective element of the custom or the opinio juris helps in distinguishing custom from an action followed as a matter of choice or for other reasons. It must be inferred from all the circumstances and not merely from the details that constitute the material element of the customary rule. 

• How does a practice or custom become customary international law

The International Court of Justice in the North-Sea Continental Shelf Case laid down four pre-requisites that must be satisfied for a practice or custom to become law under Article 38(1)(b):

• Uniformity and consistency of practice

In the Asylum Case the ICJ recognised the need for custom to be uniform and consistent. This is interpreted from Article 38(1)(b) which refers to international custom ‘as evidence of a general practice accepted as law.’

• Generality of practice

For a rule to be recognised as an international custom it is not necessary for it to be uniform however, it should be generally observed by numerous States. There has to be a sufficient degree of participation by the States whose interest depends upon the enactment of the customary law. Following are the State Practices that are generally accepted as evidence of custom: 

1. Treaties between States
2. Judicial decisions of the municipal and international court
3. Juristic opinions
4. Similar provisions in the national laws
5. Practice of international organs
6. Diplomatic relations between states

• Long duration with wide acceptance

Duration plays a significant role in determining the standing of a custom in municipal law. However, immemorial antiquity is not given much emphasis in international law, provided generality and opinio juris of the practice are proved. Customs regarding space law and continental shelf was given legal backing on the global platform somewhat quickly.

• Opinio juris et necessitatis

The State practice, even when it is consistent and widely accepted, is not a customary law, unless it is accompanied with the ‘psychological element’, that is opinio juris et necessitatis, meaning, an opinion of law or necessity. It is the thin line that connects usage to custom. The International Court of Justice in the Nicaragua case held that if the opinio juris or legal obligation of usage can be proved, it will turn into an international custom. Further, a custom can only bind a few States, as they are ‘regional legal traditions.’ In the case of Right of Passage over Indian Territory, the claim of Portugal over the right of passage between the Portuguese enclaves in India was upheld by the court, as there existed a general and uniform practice that allowed free passage. Moreover, the practice was accepted as law by both the parties, until it was challenged by India. This custom only applies between India and Portugal, and no other State can benefit from this rule.

• General principles of international law

The general principles of international law is the third source of international law recognised under Article 38(1)(c). This provision comes into picture when other traditional sources, such as the treaties or customary law does not provide a rule of decision. However, the term ‘general principles of international law as applied to the civil nations’ is vague, and many scholars have tried to interpret it. It has been debated for long whether or not they constitute a valid source of international law. Professor Schlesinger refers to general principles as “a core of legal ideas which are common to all civilized legal systems.” In the North Sea Continental Shelf Cases, the ICJ opined that the term ‘civilized nations’ should not be added as a legal element to evidence General Principles. Such a phrase would be discriminatory and against the United Nations Charter that promotes the equality of all members and non-members. However, there are a few principles that have been employed by the courts while pronouncing judgements. They can be considered as the general principles of international law. 

• Reparation and remedies

Reparation means the damages paid to the injured party caused by an unlawful act of the other party. The purpose of reparation is to re-establish the situation that existed before such harm occurred. International courts in various judicial decisions have recognised reparation as a part of general principles. In the case of AMCO Asia Corporation & Ors. v. The Republic of Indonesia, the Permanent Court of Arbitration while awarding damnum emergens or reparations to the injured party, held that it is a common principle of municipal law and, hence it is also considered as a source of international law through general principles.

• Prescription

Prescription refers to the acquisition of territory by an adverse holding, peacefully without protest continuously for a long time. It is recognised both in domestic and international law cases. The principle has been used in multiple cases by the international courts. In the Island of Palmas case, the  Arbitration Court applied this principle while pronouncing the judgment. The United State in 1928 argued that the Island of Palmas was rightfully theirs since at the end of the Spanish-American war in 1898, Spain ceded the territory to the USA. However, the territory was undisputed for a long time, and thus the contention of the USA was rejected by the court, and Netherland was awarded the Island.

• Res Judicata

The principle of Res Judicata is encompassed in municipal as well as international law. It is a Latin maxim which means, ‘a matter decided’, or ‘the thing has been judged’. In legal terms, once a case is finally adjudged by the court, it will be deemed conclusive and the established fact of the case shall not be disputed by either of the parties again in the higher courts. The doctrine was applied by the ICJ in the Chorzow Factory case, wherein an appeal by Poland to reopen the issue of fact of the case was rejected by the court on the ground of rule of res judicata.  

• Estoppel

Estoppel is a rule of national as well as international law that bars a party from leading evidence that is inconsistent with his prior conduct and facts against the opposite party. A person should not benefit from his own inconsistency and prejudice of another party. However, the principle is not applicable in those cases where the person seeking it benefits from such discrepancy. In the Tinoco Concessions Arbitration Case, Costa Rica benefited from the inconsistency of statements by Great Britain, and thus the Arbitration Court rejected the plea of estoppel by Costa Rica.

• Judicial decisions and juristic writings

These are the subsidiary or secondary sources of international law that are regarded as the interpretations of the primary sources. They are recognised under Article 38(1)(d) of the Statute of the International Court of Justice. However, according to Article 59, the decisions of the ICJ are not binding, except on the parties involved and in respect of that particular case only. Thus, the doctrine of precedent that is applicable in the national courts, is not applicable in the international courts. Moreover, every juristic writing is not accepted as a source of law. The teachings of most highly qualified publicists are regarded as the subsidiary source of international law. They are generally accepted as evidence of the law, rather than the source of law.

Ex Aequo Et Bono

The maxim Ex Aequo Et Bono encapsulated in Article 38(2) implies that a case can be decided on merit, or based on equity and good conscience of the court, rather than the law specified under Article 38(1). It allows the court to go outside the realm of the codified edict. This maxim is applied only with the mutual agreement of all the parties and not otherwise.

Hierarchy of norms

Whether there is a hierarchy of norms in international law is arguable, as there is no such hierarchy according to Article 38 of the Statute of ICJ. However, certain principles in international law are of utmost importance and should be observed by all States. These rules gain the status of jus cogens, which is peremptory norms from which no derogation is allowed. Article 53 of the Vienna Convention recognizes the principle of jus cogens. It states that a treaty which departs from the doctrine of peremptory norms of international law shall be void. Three principles that must observe the rule of jus cogens are as follows: 

1. Those exist in the common interest of the whole international community. 
2. Those created for humanitarian purposes. 
3. Those introduced by the UN Charter against the threat of use of force in international relations.

Modern/ unconventional sources

International law is dynamic and fast-changing with time. The list of sources of international law codified in the statute of ICJ is not exhaustive. It takes into account the changes in the international law community and recognizes the emerging modern sources. These sources act as evidence of the existence of traditional sources. The modern sources include decisions of the United Nations and its organs, and other international organisations. 

• United Nations

The United Nations is an international organization formed in 1945 that comprises 193 members. The organization aims to maintain international peace and security and develop friendly relationships among the nations. It has six organs, namely, the General Assembly (UNGA), the Security Council (UNSC), the Trusteeship Council, the Economic and Social Council, the International Court of Justice, and the Secretariat. The decisions and resolutions of the UNGA, UNSC, and ICJ are the key sources of law. While ICJ is considered as a traditional source, UNGA and UNSC are categorized under unconventional sources.

• Resolutions of UNGA

The General Assembly is the principal organ of the UN that comprises all the State members, each having one vote. The resolutions passed by the UNGA are not considered to have an authentic legislative character, meaning it does not have any binding force on the State members or the ICJ. However, the resolutions and decisions may have normative value. They sometimes provide significant evidence to establish the existence of a rule or an opinio juris, without which international custom is not recognized.

• Resolutions of UNSC

The Security Council is responsible to preserve global peace and safety. There are 15 members in the Council, including five permanent members. The meeting of the Council takes place only when the members feel that world peace is at risk. According to Article 25 of the UN Charter, the resolutions of the UNSC that enforces the measures in Chapter VII of the Charter, are legally binding upon the State members. However, there are controversies regarding the binding force of other resolutions. The advisory opinion of ICJ regarding the issue of Namibia states that Article 25 applies to all the resolutions adopted in consonance with the Charter and not just to the measures in Chapter VII otherwise, the object of the Article goes unfulfilled. Since it was an advisory issued by the Court, it was opposed by some States. Thus, the applicability of Article 25 is still in question, nevertheless, the underlying binding principle of the provision is unanimously upheld by all the State members and the international courts.

Conclusion

The sources of international law cannot be isolated into separate water-tight containers. They interact closely and influence each other. A treaty, which is a set of codified rules now is a product of long evolution that might involve custom, discussion and deliberations by the international organizations. Many times customary international laws are turned into treaties through codification. The covenants are then interpreted and implemented by the world court and municipal courts, which becomes another source of international law. Various new sources have also emerged from the interactions between the existing sources of law. Thus, the key to understanding one source is to study it in relation to other sources.

References

• https://treaties.un.org/Pages/Overview.aspx?path=overview/glossary/page1_en.xml#:~:text=Unlike%20reservations%2C%20declarations%20merely%20clarify,at%20the%20time%20of%20signature.
• https://www.diakonia.se/en/IHL/The-Law/International-Law1/Sources-of-IL/#:~:text=The%20main%20sources%20of%20international,law%20recognised%20by%20civilised%20nations.&text=Treaties%20and%20Conventions%20are%20written,such%20are%20obliged%20to%20follow.
• https://repository.law.umich.edu/cgi/viewcontent.cgi?article=1664&context=mjil
• https://www.law.kuleuven.be/iir/nl/onderzoek/opinies/ecbiUDsfinal.pdf
• https://legal.un.org/avl/pdf/ls/greenwood_outline.pdf
• http://www.humanrights.is/en/human-rights-education-project/human-rights-concepts-ideas-and-fora/part-i-the-concept-of-human-rights/sources-of-international-law
• https://www.univie.ac.at/intlaw/sources.pdf
• https://www.slimstuderen.nl/uploads/inkijkexemplaar/Inkijkexemplaar%20law.pdf

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