Chapter 2: Sources of International Law

Introduction

Rules and norms of any legal system derive authority from their respective sources. The ‘source’ articulates what the law is and where it can be found. In a developed legal system, sources may be readily identifiable in the form of legislation and judicial decisions. However, this is not the case for international law. The term ‘sources of international law’ is riddled with many difficulties. Jurists of international law do not agree on the very concept “sources.” This term is often colored by the doctrinal philosophy regarding the basis of international legal obligation, i.e., law of nature or positivism. According to Oppenheim, the sources of the rule of law are necessarily related to the basis of the legal system as a whole (1992). A distinction has also been drawn between formal sources and material sources of international law. According to Salmond: “A formal source is that from which a rule of law derives its force and validity. The material sources, on the other hand, are those from which is derived the matter, not the validity of the law. The material source supplies the substance of the rule to which the formal source gives the force and nature of law” (Salmond, cited in Harris and Sivakumaran, 2015: 16).

The Concept of ‘Source’ in International Law

Sources of international law are not as explicit and accessible as those of municipal law, nor is the machinery for their identification comparable to municipal law. However, the internationally accepted classification of sources of international law is formulated in Article 38 of the Statute of the International Court of Justice. These sources are:

• International conventions, whether general or particular, establishing rules expressly recognized by the contesting States;
• International custom, as evidence of a general practice accepted as law;
• The general principles of law recognized by civilized nations;
• Subject to the provisions of Article 59, 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.

Hierarchy of the Sources of International Law

Treaties, custom, and general principles of law are the main sources of international law, judicial decisions and juristic work on international law fall into the category of subsidiary sources. Accordingly, the sources of international law are:

1. Custom
2. Treaties
3. General principles of law
4. Subsidiary sources
5. Other sources

International Custom

Custom is a habitual course of conduct or general practice accepted as law. Custom evolves after a long historical process culminating in its recognition by the community. Custom may be treated as a source of law if it manifests the attributes of antiquity, certainty, continuity, consistency, and uniformity.

There are two requirements for a custom to be accepted as law: (i) there should be sufficiently uniform general practice accepted as law, and (ii) the belief that such a practice is obligatory. Consequently, for a practice or usage to become a customary rule of international law, the following two factors are essential:

• A material fact: in similar circumstances States act similarly, in other words, usage has been constantly and uniformly practiced by States.
• A psychological element: (opinio juris sive necessitatis) (an opinion of law or necessity) - the feeling on the part of States that in acting as they act they are fulfilling a legal obligation.

State Practice

State practice is fundamental to the formation of a custom, but what amounts to a State practice and what constitutes a State practice may cover every activity of the State organs or officials in an international context. It may include treaties, diplomatic correspondence and relations, opinions of national legal advisers, national legislation, policy statements, press releases, official manuals on legal questions, executive decisions and practices, decisions of international and national courts, and the practices of international organizations. Broadly speaking, State practice can be categorized into three groups as evidenced: (a) in the mutual relations among States, (b) in the practice of international organizations, and (c) the unilateral practices of States.

Opinio Juris Sive Necessitatis

The State practice, even though general and consistent, is not customary law unless an opinio juris or “psychological element” is present, i.e., the practice is recognized as obligatory and there is the conviction that its repetition is the result of a compulsory rule. In the North Sea Continental Shelf cases, the Court observed that (1969, p. 44): “Not only must the acts concerned amount to a settled practice, but they must also be such, or be carried out in such a way, as to be evidence of a belief that this practice is rendered obligatory by the existence of a rule of law requiring it. The need for such a belief, i.e., the existence of a subjective element, is implicit in the very notion of the opinio juris sive necessitatis.” Thus, the frequency or even habitual character of the acts is not in itself enough. In the S.S. Lotus case (France v. Turkey, 1927), the PCIJ laid down a stricter requirement for customary rule to evolve. In this case, the French ship S.S. Lotus had collided on the high seas with the Turkish vessel Bozkurt, killing thereby eight Turkish nationals. When the Lotus arrived in Turkish waters, criminal proceedings were instituted in the Turkish courts against Lieutenant Demons, the captain of Lotus, and he was sentenced to eighty days’ imprisonment and a fine of twenty-two pounds. Before the PCIJ, the French Government argued that under the customary international law, criminal jurisdiction pertains to the flag State of the vessel in which the crime is committed. It argued that the alleged rule exist in the State practice. The State courts had generally abstained from exercising criminal jurisdiction in deference to the flag State. This has manifested the tacit acceptance of the rule by States. The Court rejected the French contention. It observed that it merely shows that States in practice had abstained from instituting criminal proceedings, and not that they had recognized as being obliged to do so. It stated that “only if such abstention were based on their being conscious of having a duty to abstain would it be possible to speak of an international custom” (p. 28).

There has been a marked decline in the importance of customary law in present times. The principal reasons of this decline are as follows:

• There are about 200 States in the international system with different political, economic, and legal structures that participate in the law-creating process. Therefore, the growth of a new custom will always be a slow process. Moreover, not all states can keep pace with social and legal changes in international relations.
• The question of whether a particular usage has crystallized into a custom and has become obligatory is riddled with many difficulties. It is particularly so when there is no agreement about its existence. It is for the courts to ascertain a rule from the mass of heterogeneous documents, State practices, and State judicial decisions as well as to establish the legal authenticity of this rule.
• Customary law is an unsuitable vehicle to manage and respond to new scientific challenges especially in such areas as outer space, the deep seabed exploitation, and environmental issues (Friedmann, 1964).

Treaties as a Source of International Law

Treaties (conventions) constitute the most important source of modern international law. Addressing the needs of modern international society and keeping pace with the changes in international relations make it imperative to develop international rules. This can be accomplished only through concluding treaties among nation States and not by the slow process of creating customary law. In international society, where there is no equivalent to State legislation, international treaties are the closest to it, though not as perfect. The importance of treaties is self-evident, because under Article 38(l)(a) of the Statute of the ICJ ‘conventions’ have been mentioned as the first recourse which the Court is directed to resort for settling a dispute between the parties.

Treaty as such is akin to a private law contract, creating rights and obligations for the parties. Since treaty is contractual in nature, its being a source of law is debatable, as it primarily creates obligations for the parties thereto. It does not ipso facto (by that very fact) bind the non- signatories except the treaties that are “constitutive” or “dispositive” in nature. In other words, treaties establish a special régime, international boundaries, or an international institution. They create rights and obligations for third parties.

General and Particular Treaties

Treaties have been classified into “general” and “particular”, as is done in Article 38(l)(a) of the Statute of the ICJ.A convention may be general either because of the number of parties (as being accepted by a large number of States), or because of the nature of its contents (which is of universal importance). It may be particular because of the limited number of parties, or because of the limited character of its subject-matter. On this basis, some jurists have further classified the treaties into lawmaking treaties and treaty contracts. Whereas the law-making treaties are a source of law, the treaty contracts merely purport to lay down special obligations between the parties and are not directly a source of law.

General Principles of Law

The term “general principles of law recognized by civilized nations” in Article 38(l) (c) of the Statute of the ICJ is relatively vague. The phrase applies to fundamental principles of justice that have been accepted and adopted by “civilized nations.” It includes, though not confined to, the principles of private law administered by municipal courts, as applicable to international relations. The Court can have recourse to this source if there is no convention or any clear rule of customary law in a case before it. This is also considered necessary to avoid any situation of non-liquet, i.e., the possibility that a court or tribunal would be unable to decide a case because of a “gap” in the law. An international judicial body is under a duty to adjudicate, and it should not refrain from giving judgment on the grounds that the law is silent or obscure.

Acceptance of General Principles as a Source of International Law

Some jurists such as Alfred Verdross opine that Article 38(1)(c) has the effect of incorporating natural law into international law and that any rule of international law if in conflict with natural law is invalid. Judge Gerald Fitzmaurice also states that this provision involves necessary principles of natural law. He cites many examples in its support, including the one that a State cannot put the deficiencies of its internal law to be excused from performing its international obligations or impossibility of performance arising out of a situation brought about by the State itself. Positivists contest the validity of general principles as a source of international law on the grounds that consent is the basis of international law. Jurists such as Guggenheim and Tunkin maintain that para. (c) of Article 38(1) adds nothing new to the existing sources of international law, i.e., custom and treaties. The main apprehension of positivists seems to be the development of international law through judicial action instead of exclusively by States. The third view, endorsed by a majority of jurists, holds that these principles are already there as part of international law. They opine that Article 38(1) (c ) adds “a flexible element that enables the Court to give greater completeness to customary law and in some degree to extend it” (Waldock, cited in Harris and Sivakumaran, 2015: 36).Despite these controversies, however, the preponderant opinion is that general principles recognized by national tribunals constitute an inexhaustible reservoir of principles, which international tribunals are authorized by Article 38 to apply in an international dispute.

Judicial Application of General Principles

The Permanent Court of International Justice and the International Court of Justice, while relying on general principles as a source, frequently either referred to the customary law or left it ambiguous as to whether they are general principles of national law or of international law. At any rate, by applying the general principles of law, these Courts do not make new law but acknowledge that a principle found in all municipal legal systems is a general principle of law and, as such, is also present in international law.

Subsidiary Sources of International Law

Article 38 of the Statute of the International Court of Justice identifies two subsidiary means for the determination of rules of law: a) judicial decisions, b) the teachings of the most highly qualified publicists of the various nations.

Judicial Decisions

Article 38(l) (d) of the Statute of the Court puts “judicial decisions ... as subsidiary means for the determination of rules of law.” This invariably refers to international judicial decisions, State judicial decisions, and decisions of international arbitral tribunals. They are called “subsidiary means,” because in the normal conduct of international relations it is the State practice that creates international legal rules. In theory, judicial decisions do not constitute a formal source of law; in practice, however, they play a substantial role in the development of international law. When the State practice is either ambiguous, non-existent, sparse, or contradictory, courts get involved in determining the rules of law in order to decide a legal issue and in this process they create new rules. Decisions rendered by the courts are of immense value; and in those cases where there is no preexisting rule, these decisions become a direct source of law.

Teachings of the Publicists (Juristic Work on International Law)

Although Article 38 of the ICJ’s Statute confers “subsidiary” status to “the teachings of the most highly qualified publicists,” they are an important source of international law. Juristic writings made substantial contribution especially in the formative period of modern international law. In this process, publicists made use of natural law principles, analogies from Roman law, and generalization of State practice whenever possible. The writings of Gentilis, Pufendorf, Grotius, Bynkershoek, Van Martens and Vattel, among others, had enormous influence in the development of international law. However, the creative role and influence of publicists seems to have declined nowadays, and the judicial bodies such as the ICJ have taken a more active role in determining and pronouncing international rules.

Other Possible Sources of International Law

Apart from the above-mentioned sources in paragraph 1 of Article 38, other sources of international law have also emerged and received a fair mention in the judgements of the Court. Paragraph 2 of Article 38 mentions deciding a case ex aequo et bono. Article 38, however, is silent on the decisions, determinations or practices of the international organs or institutions such as the UN General Assembly and the UN Security Council, though they are increasingly becoming important in the development of international law. This could be for the reason that when the Statute was drafted, the importance of these organs in law-making was not contemplated.

Equity and ‘Ex aequo et bono’

If the dispute cannot be decided by applying the provisions of clause (1) of Article 38, clause (2) empowers the ICJ to “decide a case ex aequo et bono, if the parties agree thereto. Ex aequo et bono is a Roman Law concept, means ‘according to what is fair and good.’ This is different from the principle of ‘equity.’ A case decided ex aequo et bono is not decided on the basis of law but on the basis of “such other considerations as the court may in all the circumstances regard as right and proper.” It is based on the principles of “justice, equity and good conscious.”

Resolutions and Declarations of the UN General Assembly

The UN General Assembly has adopted numerous resolutions since its inception on issues ranging from human rights to consumer rights. These resolutions are not legally binding per se, but they can spell out and, to some extent, elaborate on the existing customary rules as well as contribute to the rapid formation of new rules. In this sense, they have great evidentiary value. They have proved to be very valuable when it comes to the interpretation of the provisions of the UN Charter and developing new laws for areas made accessible by modern science and technology such as outer space or deep seabed.

Soft Law

Soft law consists of written instruments that spell out rules of conduct that are not legally binding and do not generate the requisite opinio juris contributing to customary rules but that lay down the trend for the future development of law. Since not being legally binding, they cannot be enforced in a court (though the ICJ has taken note of them, e.g. the Nicaragua case 1986, para 189). The concept of soft law is useful in that it may act as the basis for a treaty or strengthen a customary rule. Examples of this can be found in the 1948 Universal Declaration of Human Rights, the 1972 Stockholm Declaration, and the 1975 General Assembly Declaration on the protection of all persons from being subjected to torture, followed by the 1984 UN Convention against Torture.