7 Opinio juris in International law

Aditya Swarup

Introduction

In recent times the behavioral relations between states and international organizations have come to be regulated by international law, an important element of which is custom. An act is said to have the binding force of a custom when it entails in its ambit two main elements; state practice and opinio juris. The aim of this module is to understand and analyze the concept of opinio juris, the psychological element of custom, which serves as the belief of a state as having a legal obligation to perform or to not perform a particular act. Given its subjective nature, opinio juris is difficult to evidence and subject to intense debate in the international law arena. The module thus is focused on highlighting the complexity of the doctrine through theoretical concepts and understanding its application by examining judgments delivered by international Courts and Tribunals.

However, the doctrine of opinio juris cannot be be understood in isolation. The module thus begins by giving the reader a detailed background of the sources of international law, customary law and state practice. The next section of the module is focused on the theory of opinio juris followed by a section analyzing the application of the theory in cases before the International Court of Justice (ICJ). The module has been designed to engage the reader and includes a variety of illustrations, reflective questions and self help exercises to ensure conceptual clarity. The module concludes with a brief summary and answers to the questions posed throughout the module.

Learning Outcomes

• What is the basic understanding of Opinio Juris in international law?
• From an Indian perspective, how does one look at the relevance of the concept?
• How does Opinio Juris help in evaluating practices and custom in international law?

Background

2.1 Sources of international law

To understand the role of opinio juris in international law, it is essential to understand the origin of international law in the first place. Article 38(1) of the International Court of Justice Statute is widely recognized as the most authoritative statement on the sources of international law. It reads as follows:

Given that the function of the ICJ is to decide disputes ‘in accordance with international law’ and by virtue of Article 93 of the UN Charter, all UN members are automatically considered to be parties to the ICJ, it is generally accepted that Article 38(1) is universal in its application.

2.2 Customary law

Article 38(1)(b) of the Statute lays down the principle of customary law, which is one of the primary sources of international law rules that govern the relationship between sovereign states. The element of unwritten rules and implied consent of the state to the same, is what gives customary law its binding force. This principal, though difficult to define, has a wide ranging effect, for it tends to unilaterally bind states and serves as an important philosophic basis in the international law arena.

Customary law, for the resolution of disputes, commands that it should be resolved by respecting and adhering to the different customary practices of different states. Though this seems straightforward, but given that customary law should have the “evidence of a general practice accepted as law”, the threshold for proving the same is actually quite high and often difficult. In order to reach that threshold, the court must consider both the the practice and behavior of states. This means that customary law entails in its definition two distinct elements:

Material Facts or what is also known as state practice

Opinio Juris or the subjective belief that an act of the state is mandated by law

The fundamental importance of these elements was judicially established by the ICJ in the Nicaragua case of 1986, followed by the case of Malta v. Libya, wherein the court opined that the assessment of the actual practice of the state as well as opinio juris, is what establishes the core of customary law.

Food For Thought!

What happens in cases where the States action is motivated simply by goodwill and not by the belief of being bound by a legal rule? How does one determine the precise nature of action by a state?

It is interesting to note that the relative importance of the two factors has often been disputed. Positivists, who emphasize state sovereignty and consent, stress upon the paramount importance of opinio juris, i.e. states are only bound by what they have consented to while other scholars take the opposite view, that focuses on state practice and the belief that opinio juris is impossible to prove and thus irrelevant in international law.

2.2.1 Material facts OR STATE PRACTICE:

This is the objective element that ought to be satisfied for a custom to qualify as a rule of customary law. It affects the manner in which the rules of customary law are to be applied to the country in question. The authenticity as well as the applicability of the customary practice is influenced by a variety of factors like its uniformity and consistency, the duration for which the practice has subsisted, the generality of the practice the repetition of its use. However, judicial opinion has affirmed that these standards are exclusive to one another and further that all of them may not be fulfilled in each case to determine the validity of the practice.

For state practice, no rigid standards as to a ‘long passage of time’ are required to be met and the evidence of the same will vary depending upon the facts and circumstances of each case. For instance, in certain fields like air and space law, the rules have developed quickly, while in other fields the process has been much slower. One may thus conclude that duration not the most important component of state practice.

Further, the element of uniformity is not absolutely but only substantially essential. What this fundamentally means is that uniformity in substance is the necessary pre-requisite i.e. only to a certain degree of uniformity, if not more. Similarly, in terms of the element of consistency, it is essential that the practice is substantially consistent and not absolutely. This requirement makes it easy for one to gauge the stability of the practice in question. For a custom to become a rule of international law that regulates state behavior, it must emanate a certain level of durability. It has often been argued that this durability, of a practice that is consistent and uniform, is often determined by the duration for which the practice has been undertaken. The ICJ thus has opined that state practice has to be both ‘extensive and virtually uniform’ in relation to the provision invoked, but it is not necessary to have ‘absolutely rigorous conformity’. The following observations of the ICJ shed more light on the issue:

Nicaragua Case: “In order to deduce the existence of customary rules, the Court deems it sufficient that the conduct of states should, in general, be consistent with such rules, and that instances of state conduct inconsistent with a given rule should generally have been treated as breaches of that rule, not as indications of the recognition of a new rule.”

Asylum Case: ” The party which relies on the custom.. must prove that this custom is established in such a manner that it has become binding on the other party.. that the rule invoked.. is in accordance with a constant and uniform usage practiced by the States in question..”

A custom should also have sufficient practice i.e. it should reflect the ideas of the majority of states. But the fact that certain states are more influential and powerful than others in the creation of international legal rules, is incontestable. However, this does not imply that customs can only be created by majority states. They can be created by minority states as well but they require a close connection of the influential states to the issue at hand. For instance, the role played by United Kingdom in the development of the ‘Law of the Sea’ in the 19th century. Thus one can conclude that for a custom to be accepted and recognized, it must either have the concurrence of a majority of states or at least the major players or powers in that field.

1. Instant Custom:

Instant Customs are those that do not require repetition or a long duration of consistent practice to develop as a customary rule—Eg: Customary law relating to a state’s sovereignty over its airspace developed very quickly in the years immediately before and during WWI. Similarly, principle of non-sovereignty over space route followed by satellites came into existence shortly after launching of first sputniks

Opinio Juris

Opinio juris sive necessitates is the subjective element necessary to form customary law. It focuses on the jurisprudence of the country whose custom is in question and ensures that there is a conscious allowance or enforcement of the practice by the country, even if such practice is already customary.

Further, it is reflected in instances where the state undertakes a particular practice because it believes that it is legally bound to do so i.e. to turn a practice into a custom and in turn to make it a part of the rules of International law, the concern of the doctrine is only on the belief of the practice being ‘legally obligatory’ in nature. It also distinguishes between custom and usage.

Thus, post the establishment of the existence of a specific practice, one must consider how the state views its own behavior and whether it regards it as a moral, political, or legal act? Opinio juris facilitates this separation of international law from the principles of morality or social conventions, for states may not restrict their behavior to only what they are legally obligated to perform but may pursue conduct purely from a feeling of goodwill and reciprocal benefits.

The emphasis of opinio juris is on the psychological element so required to form a custom. The sense of being legally obliged as opposed to feelings of mere courtesy must be distinctly detectible to the state for it to be able to draw a distinction between a custom (which is a general practice that reflects a legal obligation) and mere usage (which reflects a general practice without an obligation). Ian Brownlie suggests that to differentiate between acts which are legally obligatory on the state and which are not, the ICJ has adopted two distinct approaches. The first approach is where the court has relied on the opinions of other legal authorities to determine the existence of a particular rule while the second approach, which is a lot more rigorous and less common, is where the court has sought positive evidence of the adoption of the rule by the state.

Rules that remain only usage and have not yet materialized into law are known as lex Fernanda, while the rules of international law that have a legal effect are known as lexlata. It is further important to note that generally where states are seen as acquiescing in the behavior of other states without protecting themselves, the assumption is that such behavior is accepted as legitimate.

Once a rule has become customary law, it is binding on all states except for a “persistent objector”. These are states that have dissented and raised objections to the rule from the very beginning. However, it is even more pertinent to note the inherent contradiction in the doctrine of opinio juris. As per this doctrine, states are required to believe that something is already law before it can become law i.e. state officials must be convinced of the binding force of the law as a pre-requisite to customary law. This paradox is point of debate among various scholars in international law.

Regional or Local Custom

Rules may develop in a way that they bind only a set group of states in a given region, or just two states in their dealings with one another. This is usually done to respect regional legal traditions. The standard of proof in such cases is generally higher than when trying to establish a general custom, for it might need acceptance by every single state in that region.

Eg: Right of Passage over Indian Territory case in ICJ: Portugal had claimed that there existed a right of passage over Indian territory as between the Portuguese enclaves, and this was upheld by the ICJ over India’s objections,for the court was satisfied that there had in the past existed a constant and uniform practice allowing free passage and that this practice was accepted as law by the parties

How do you think this is different from a general rule of customary law?

3.1 Case Law analysis

The significant role played by opinio juris in customary law has time and again been highlighted by International Courts. ICJ has adopted and maintained a high threshold for proving the subjective element of the rules. Various case laws highlighting the same have been discussed below:

The case of S.S Lotus (France v. Turkey):

The Lotus case gives an important dictum on creating customary international law Two ships, the French ‘Lotus’ and Turkish ship ‘BozKourt’ collided on high seas which resulted in the death of many aboard the Turkish ship. Upon the arrival of Lotus in Istanbul, the French officer was accused and arrested for manslaughter. The issue at hand concerned whether Turkey had the jurisdiction to try the French officer in question. French authorities argued that it was only the flag state of the accused, which is France in this case would have the exclusive jurisdiction to try the accused and not the victim state, which is Turkey. France attempted to evidence the same by stating the absence of ‘previous criminal prosecutions by such states in similar situations’ and from this assumed consent in the practice, which therefore became a legal custom.

The Court rejected this and declared that even if in fact, such a practice of abstention from instituting criminal proceedings could be proved, it was not a custom with a legally obligatory character. It held that this “…would merely show that states had often, in practice, abstained from instituting criminal proceedings, and not that they recognized themselves as being obliged to do so; for 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. The alleged fact does not allow one to infer that states have been conscious of having such a duty; on the other hand, as will presently be seen, there are other circumstances calculated to show that the contrary is true.”

The case of North Sea Continental Shelf:

The question in the present case was whether Article 6 of the Geneva Convention on the Continental Shelf of 1958 was a rule of customary law. Article 6 of the Convention had provided that for the determination of the boundary line of states where no agreement could be concluded between them, and unless circumstances of a special nature justified an alternate approach, the boundary line must be determined as per the equidistance principal from the points of the baselines that were nearest and from which the breadth of the territorial sea of each state is measured. The Court did not find the said article to be reflective of an already existing custom.

The Court noted that even in the draft treaty, the principal of equidistance had been introduced with great hesitation which signifies that the the principal was experimental at best and definitely not a rule of customary international law that was binding upon the states. Commenting on the nature of binding rules and principles the court further noted that for a new customary rule to be formed, not only must the acts concerned ‘amount to a settled practice’, but also they must be ‘accompanied by the opinio juris sive necessitatis’. Either the States taking such action or other States in a position to react to it, must have behaved so that their conduct is “evidence of a belief that this practice is rendered obligatory by the existence of a rule of law requiring it.” The relevant portion of the judgment reads as follows:

“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. The States concerned must therefore feel that they are conforming to what amounts to a legal obligation. The frequency, or even habitual character of the acts is not in itself enough. There are many international acts, e.g., in the field of ceremonial and protocol, which are performed almost invariably, but which are motivated only by considerations of courtesy, convenience or tradition, and not by any sense of legal duty.”

The case of Nicaragua v. USA:

Similar to the aforementioned case, here too the Court reflected on the importance and the essential nature of both state practice and opinion juris in the formation and elucidation of a rule of customary law. The case even clarified that just because the state practice is inconsistent does not mean that the rule in question can no longer be formed or continue to remain a rule of customary law as long as the inconsistency of the practice can be justified as a breach of the rule.

“It is not to be expected that in the practice of States the application of the rules in question should have been perfect, in the sense that States should have refrained, with complete consistency, from the use of force or from intervention in each other’s internal affairs”

The case further explained how one could deduct opinio juris from acts of State i.e. the evidence of the subjective belief could be evidenced from the following sources:

“..the attitude of States towards certain General Assembly resolutions. For example, the “Declaration on Principles of International Law concerning Friendly Relations…” (hereafter, called the Declaration on Friendly Relations). The Court held that:

The effect of consent to the text of such resolutions cannot be understood as merely that of a “reiteration or elucidation” of the treaty commitment undertaken in the Charter. On the contrary, it may be understood as an acceptance of the validity of the rule or set of rules declared by the resolution by themselves…It would therefore seem apparent that the attitude referred to expresses an opinio juris respecting such rule (or set of rules), to be thenceforth treated separately from the provisions, especially those of an institutional kind, to which it is subject on the treaty-law plane of the Charter.

• Statements by State representatives.
• Obligations undertaken by participating States in international forums (the Court provided the example of the Conference on Security and Co-operation in Europe, Helsinki)
• The International Law Commission’s findings that a concept amounts to a customary law principle.
• Multilateral conventions..”

One may thus conclude that the essence of opinio juris is reflected in the omission of the states, as was in the Lotus case, or in the acts of the states, like the Nicaragua case. What is important however, is that whether an act or an omission, it must be done by the state with a belief that it is obligated in law to act or not act in a particular manner.

Summary

The sources of international law are derived from Article 38(1) of the ICJ statute, which is the most authoritative source on the same. It lists customary law as a source of law.

Customary law entails two elements- Opinio Juris and State Practice. While state practice is objective and is reflected in the acts of the state, opinio juris is subjective and is difficult to prove for it a psychological element required to form custom.

State practice must be uniform and consistent though not absolutely.

Opinio juris is motivated by a sense of legal obligation i.e. the state must believe that it is bound by law to do or to not do a certain act. Only when state practice combines with the belief that the state of legally obligated to perform (or not perform) an act is it a custom, else it is called usage.

Rules that remain only usage and have not yet materialized into law are known as lex Fernanda, while the rules of international law that have a legal effect are known as lexlata.

Reference

• The case of Columbia v. Peru (1950), also called the Asylum case. In particular, see paragraphs 14 and 15.
• http://www.icj-cij.org/files/case-related/7/1851.pdf
• The case of Portugal v. India (1960), also called the Rights of Passage case. In particular, see paragraphs 42 and 43.
• http://www.icj-cij.org/files/case-related/32/4523.pdf
• ICJ advisory opinion on the Legality of the Threat or Use of Nuclear Weapons. In particular, see paragraph 70 on the use of General Assembly Resolutions to establish opinio juris.
• http://www.icj-cij.org/files/case-related/95/095-19960708-ADV-01-00-EN.pdf