Here I will throw some light on the evolution of customary international law through different state practices and how it different it is from the evolution of humankind. But first, we need to understand what amounts to international law, that is, what are the sources of international law.

Article 38 of the Statute of the International Court of Justice directs to the court as to where to look for the law.

ARTICLE 38

The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply:

a. international conventions, whether general or particular, establishing rules expressly recognized by the contesting states;

b. international custom, as evidence of a general practice accepted as law;

c. the general principles of law recognized by civilized nations;

d. 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.

This provision shall not prejudice the power of the Court to decide a case ex aequo et bono, if the parties agree thereto.

Thus, broadly speaking the following are the sources of international law;

• Customs

• Treaties

• The General Principle of Law Recognized by Civilized Nation

• Judicial Decision

• Juristic Work on International law

• General Assembly Resolution and Declaration

The most historic and most important source of international law is customs. Though its importance has lessened in modern times due to the increasing use of treaties and conventions as a law creating method, it still remains a vital source of international law. Customs has played a significant part in building the present fabric of the international legal system.

A custom is an accepted way of behaving or of doing things in a society or a community.

In international law, customary rules are evolved after a long historic process culminating in their recognition by the community.

A customary rule of international law may be defined as a rule which the community of States has since long recognized as the right rule of conduct and which has the force of law.

Custom is a constant and uniform usage accepted as law. Following are the requirements for usage to be custom:

(I) Material fact: Similar circumstances States act similarly, usage has been constantly and uniformly practiced by States are considered as material facts.

(II) Psychological fact: The feeling States think that they are acting to fulfilling a legal duty, is a psychological fact.

It is the material fact which is significant in the establishment of customs.

Not only in international law, but customs have also played the most important role in the evolution of human societies. Every great social achievement is an outcome of our collective imagination.

Social customs are a product of our collective imagination. Everything which is not present in nature and is built by humans is only possible with the humans’ ability to cooperate.

Evolution of customary international law co-evolved with the evolution of the humankind.

In the field of international law, State practices play a fundamental role in the formation of customs.

But what are State practices?

Broadly speaking State practices includes treaties, diplomatic correspondence and relations, opinions of national legal advisers, national legislation policy statements, press releases, official manual on legal questions, executive decisions and practices, decisions on international and national courts and the practice of international organizations.

In general, a custom can be created by a practice done by few States, for a continuous period with an intention that the act is binding, it is necessary to do that act. Here, both the material fact and the psychological fact is present.

If you compare this with the evolution of ordinary customs by human interaction, for example praying to god. This particular practice also contains both the material fact as well as the psychological fact.

We must pray to god, is a psychological fact, people think that they have to pray otherwise the god will punish them, a fear of sanction. The continuous practice by god-fearing people is a material fact.

Material fact and the psychological fact are always in the formation of custom.

Opinio Juris Sive Necessitatis

What is Opinio Juris? Opinio Juris is the psychological element necessary for the formation of customary international law.

The state practice, even though general and consistent is not customary law unless an Opinio Juris or psychological element present in it. That is, the practice is recognized as obligatory and there is the conviction that its repetition is the result of a compulsory rule.

“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, that is, the existence of a subjective element, is implicit in the very notion of the Opinio Juris Sive Necessitatis. The State concerned must, therefore, feel that they are conforming to what amounts to a legal obligation. The frequency or even habitual character of the ACT is not in itself enough.”

The following paragraph is from the North Sea Continental Shelf case.

Let us look into two examples to understand what this case is all about.

Example 1.1: Two countries A and B are doing a practice for the last 100 years, let us suppose that practice is to let other country's citizen enter into their border.

Now country A has sealed their borders for the citizens of country B.

Country B objects to this new rule because the majority of its citizens’ workplace is in country A. This new rule will significantly increase the amount of joblessness in country B.

Country B takes this matter to the ICJ, country B claims that country A has violated 100 years old customary international law.

The court says that the acts of country A is not a violation of customary international law, because there was no customary international law existed between country A and country B.

This is because there was no Opinio Juris present in this case. The 100 years old practice of visa-free entry was not a result of a belief that this is obligatory.

Example 1.2: Two countries A and B, are doing a practice since last 100 years, let us suppose that practice is to let other country's citizen enter into their boarder, because both the countries think “free movement” is a human right and consider it legally binding on them.

Now country A has sealed their borders for the citizens of country B.

Country B objects to this new rule because the majority of its citizens’ workplace is in country A. This new rule will significantly increase the amount of joblessness in country B.

Country B takes this matter to the ICJ, country B claims that country A has violated 100 years old customary international law.

The court says that the acts of country A are a violation of customary international law existing between country A and country B.

Opinio Juris also exists in the formation of customs between humans. Here are another two examples to explain the importance of Opinio Juris in human life.

Example 2.1: Two human friends help each other to find food. They are helping each other for the last 10 years.

The practice of helping others in finding food is not a custom, Opinio Juris is missing.

Example 2.2: Two human friends help each other to find food because they think God wants them to help each other, and if they do not help each other, then they will be punished. They are helping each other for the last 10 years. This can become a valid custom, as the Opinio Juris is present.

From the North Sea Continental Shelf case, it is clear that for a practice to be a valid custom, it is necessary to have Opinio Juris. The frequency or even habitual character of the practice is not in itself enough to label it as a custom. There has to be a belief that the acts are binding on them, even if originally the act is not binding on them.

Two friends think the act of helping each other is binding on them by the god. In reality, there is no God. Only the belief in god is enough for the friends to help each other in good faith.

Again the belief in isolation is incomplete for a practice to become a custom. Both the material fact and the psychological fact is required.

The Belief System

In the field of customary international law Opinio Juris is an important topic. To understand this completely, let us explore a few more cases.

SS Lotus Case

In SS Lotus case a strict requirement was laid down by the court for a customary rule to evolve.

In this case a French ship ‘SS Lotus’ collided with a Turkish vessel ‘Boz Kourt’ on the high sea killing 8 Turkish nationals. When the SS Lotus arrived in the Turkish Water, criminal proceedings were instituted in the Turkish courts against the captain of SS Lotus along and the captain of Boz Kourt for manslaughter and sentenced.

The French government protested against the Turkish action and by an agreement between the parties the dispute was submitted to the Permanent Court of International Justice.

The French government argued that under the customer international law criminal jurisdiction pertains to the flag state of the vessel in which the crime is committed. The flag state was entitled to exclusive jurisdiction the court rejected the French contention.

The French lost the case because the court failed to find any psychological element in the case.

The court rejected the French contention and observed;

“The circumstances alleged by the French government merely show that states had often, in practice, abstained from instituting criminal proceedings, and not have that they recognize 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 of infer that states have been conscious or having such a duty”

North Sea Continental Shelf Case

This line of reasoning of the SS Lotus case was adopted by the International Court of Justice in the North Sea Continental Shelf case.

Where Denmark and Netherlands in their case against the Federal Republic of Germany for the delimitation of the continental shelf between them. The court found the absence of psychological element required for the creation of such a new rule. The court further said,

“there is no evidence that they s acted because they felt legally compelled to draw them in this way because of a rule of customary law obliging them to do so – especially considering that they might have been motivated by other obvious factors”

Anglo Norwegian Fisheries Case

A rule will not be binding on states which have maintained its descent throughout the rules formative period. And in the Anglo Norwegian Fishery Case, the United Kingdom argued unsuccessfully that the ten-mile rule in the case of baye was an established principle of customary international law. The court, while rejecting this contention stated that even if it has required and authorities of general international law, "it would appear to be inapplicable as against Norway in as much as she has always opposed any attempt to apply it to the Norwegian Coast.”

Jurisprudence And International Law

Let us now see the evolution of customary international law from the point of view of different jurists of law.

Austin

Austin overlooked customs in his theory. He gave no place to the judge-made law and treated international law is mere morality.

Reality Check

In reality law, society, morals and behavior are linked with each other. Considering only a sovereign making law backed by sanction limits the scope of the law, made by humans, for humans.

International law is a law made by nations, for nations, and for their proper functioning.

Many countries, who follow the theory of dualism, do not take international law very seriously, for them the international law is secondary to their constitution.

On the other hand, countries, who follow the theories of monism, treats international law and their constitution equally.

Bentham

According to Bentham’s theory of utilitarianism, a good law is a law which makes the maximum number of people happy and the minimum number of people unhappy.

If international law is making the maximum number of people happy that a countries constitution, which is only making its citizens happy, why should there be a conflict between the two? According to this theory, the international must be supreme in all cases.

Reality Check

The difference between the theories of monism and dualism boils down to morality.

But apart from morality, diversity makes everything beautiful. Just look at your self (a complex creature) and (a single cell organism).

“Beware of simple ideas and Simple Solutions. History is full of visionaries who used simple Utopian visions to justify terrible actions. Welcome complexity. Combine ideas. Compromise. Solve problems on a case by case basis.” – Hand Rosling

F K Von Savigny

Only a few points of Savigny, here I want to highlight.

One, Law develops like a language.

The term law in the above sentence refers to state law, what about international law? The evolution of international is not exactly like a language.

Customary international law might have been evolved as a language, local to particular places. However, international law made by sources other customs and treaties might not have been evolved as a language.

Two, Early development of law is spontaneous.

Law, which ever it is, evolves spontaneously in the beginning. International law is no exception.

Imagine, you and I meet in a jungle. We need to survive and fight wild animals and the cold climate. We will instantly make a few laws to suit our needs. Slowly, as time passes, the rate of development of the rules we made will slow down. I strongly recommend trying this experiment.

Three, Law is a continuous and unbreakable process.

After the rate of development of the rules might slow down in our Republic Of Jungle, but it will never stop. We will continue to make new rules according to our needs.

Hence, the theory of Savigny fits properly in the evolution of international law. Apart from his some criticism.

The evolution of customary international law was like the evolution of humankind, by natural section. Now it is slowly starting to evolve by the evolution of intelligent design.

Refrences

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5. North Sea Continental Shelf Case (1969) ICJ Rep. 3
6. SS Lotus Case (1927) PCIJ (Ser. A) No. 10
7. North Sea Continental Shelf Case (1969) ICJ Rep. 3
8. Anglo Norwegian Fisheries Case (UK vs Norway) (1951) ICJ Rep. 116
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