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This article is written by Somya Janki currently pursuing a BA LLB (Hons) from Kalinga Institute of Industrial Technology. This is an exhaustive article that discusses how the customs and cultural norms have shaped International Criminal Law.

Introduction- What is law

All of us are well-acquainted with Gulliver’s Travels. Now, our friend Gulliver supposedly committed the crime of perfidy by playing dead and has escaped from the island of Lilliput to the island of Blefuscu to save himself from the clutches of the Lilliputians. So, they send over a message to the residents of Blefuscu to hand over their prisoner. Tarry! But our friend insists upon the fact that he never did any wrong, so what should be the decision taken for this situation. At the very first place whose law would be applied here? Is it of the Lilliputians or Blefuscu? Or shall it not be of England from where Gulliver came all the way along? To decide if there needs to be a source that would prevail over all these laws or what we call International Laws or to be more specific for this case, International Criminal Law would come into play. So, what does this law state, and what is its source? So, let us delve deeper into our subject.

But halt, what is with these generic terms? What do we understand by international law and by law at the very first instance? So, if we ask any person generally, it would be different definitions based on its salient features. The prelude of the law is in the society itself. Why do we make laws? We make laws for stability, peaceful coexistence, to provide justice to all, and many more. But the primary reason behind creating these rules and regulations is for efficient governance and in fact, a state without law would be in a state of anarchy and citizens are more like a beast. So, in the words of Austin, “Law is the general command by the sovereign to his subjects which they are deemed to follow”. In simpler words, it is the command by the sovereign authority over his subjects. Law had been in existence since the time of early man in the form of cultural norms and customs. Thus, ‘Ubi societas, ibi jus’, where there is a society there is the law. The existence of law presupposes the existence of society and we have society all around us whether it is our nation-state or the group of countries or nations or the entire world. Thus, there is a certain set of laws defined for every society which brings us to the reason why we have different laws existing at both national and international levels.

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International law-classification

The concept of national and municipal laws has existed for ages and was very much accepted to provide justice, peace, stability, and maintain the government’s efficiency, which was not in the case of international law. International law is of recent origin. There were many stumbling blocks for its development. It was not considered as a branch of law owing to the view of some scholars like Austin and his other stalwarts that it lacked some of the elements that law should have. According to him, if an individual commits a wrong, the applying power must have the most power on the sovereign to impose sanctions on him. So, nothing that was solely based on ethics, morality, or good conscience could be considered laws. While there were also scholars like Kelsen who were staunch supporters of it. He emphasized the fact that international law was superior to national law and it covered national law in a certain way in it and the laws are made to prevent dishevelled structure in the society. At present, there are no more controversies over international law being another branch of law and it gains recognition from all over the world. As is evident from the different statutes through which international law derives i.e. the United Nations Charter, International Court of Justice’s Statute, etc. International law is further divided into two types:

Public International law

Public international law, also known as ‘Jus Gentium’ is a code of conduct or the body of rules that runs either between two nation-states or among more than two nation-states to maintain their relations. Generally, they do not form part of legal statutes or treatises’. They are further divided into:

Administrative law

This branch deals with the structure and organs of the international organization. It provides and restricts the power which is available for the protection of the interests of the nations or states. 

Criminal Law

It is the branch of law that defines the offences and also lays down the procedure of punishment for the offenders for their acts of deviance. The main objectives of these laws are to maintain the peace and order of the world. In a civilized world, an act of sin committed against an individual is considered an act of wrong against society. This also brings us to the point of why civil law is not a part of public law. Criminal law is considered  ‘right in rem’ that is it is applied for the whole society since a crime committed disturbs the whole society by offending the state or doing the acts which are forbidden by the society. While Civil law is ‘right in personam’ and is committed against an individual and is generally to uphold the rights of a person residing in that very state.

Private International Law

Private International Law, also known as the ‘law of people,’ consists of laws applied to resolve disputes or for arbitration or conciliation between or among individuals with a foreign element. For instance, if an Indian and Chinese make a contract in Pakistan, their terms, contractual obligations, or anything for that matter would be decided by Private International Law. It consists of all laws about the law of contracts, the law of torts, etc.

Sources of International criminal law

International Criminal Law is quite different from domestic criminal law as for a matter of fact, its formulation is not as it is in the case of municipal ones. The foremost factor is that usually these laws are formulated by a single sovereign body in a nation-state while in the case of International laws there is no highest sovereign authority as such but an organization which is an embodiment of various nation-states who have come up with a common consensus to formulate these laws. So, International Criminal Law derives its sources primarily from two areas as mentioned according to their hierarchy:


The peace treaties at war or multilateral treaties form the main source of formulating these laws. These treaties and conventions being persuasive enough and formal sources of law are also called ‘hard laws’. The centrally play the role of forming a conciliation/defence or extradition pact between or among the nations or countries. However, even if these treaties do not form part of the laws yet, they are binding on the players who have entered it has obligations to follow the terms and conditions or rules and regulations incorporated within it. According to Article 38 (1) (a) of the International Court of Justice’s Statute, the term ‘International convention’ concentrates upon the treaties as a source of creating laws and regulation and acknowledging rising among the parties who have entered into it.

International customs

The International Court of Justice’s Statute defines International custom as evidence of what is generally practiced by the law. It is the second source of laws about criminal justice at the international level. The practice of deriving custom as a source implies the decentralised nature of these bodies and it is quintessential for a custom to be accepted as a law that it is in practice in the nation-states and further it is also widely accepted by them, implying the idea of consensus-ad-idem. Along with that, there are also further requirements for a custom to be law.

However, there are some instances where international treaties also in a way act as a custom or truly become a custom. Usually, when a multilateral treaty does fall short of efficient provisions and is not agreeable to most nations, the customs come to the rescue by applying the general rule of the law. Even at times for crystallisation of international treaty, customs are required in case they are not easily identified or recognized. Further, there are also cases of what is also known as ‘instant custom’ when the provision of any treatise or convention has been recognized by the International Court of Justice itself at many instances as a general customary rule or practice then such provisions may be defined as customary law.

Custom and cultural norms as a source of International criminal law

According to Article 38 (1) (b) of the International Court of Justice’s Statute ‘international custom’ refers to the source through which international law derives which requires the fulfillment of two practices- one is that of opinio Juris sive necessitatis which is also known as opinio Juris and the feature of jus cogens. Although, treatises and conventions have replaced the customary law with the pacing time. Yet, customs do have a significant role to play in shaping the law. But as all treaties cannot become a part of the law, the same applies to the customs too, in fact, there are certain requisites for a custom to become law.

Pre-requisites for a custom to be a valid custom

For a custom or any cultural norm to become law it has to fulfill the following conditions:

Opinio Juris

Usually, for a custom to prevail as a law in nation-state practice the fulfillment of it is not required but it is not in the case of International Criminal Law where it is the fundamental requirement. According to this concept or principle, the nation-state should not only have the pretext that there is a certain notion to be followed but as a matter of fact, there should be an actual practice of such custom. But if the custom is practiced that does not create any obligatory role that it has to be accepted as a law like for instance during the time of world war nuclear weapons were much employed, now that does not give out the sound reason that it should be followed in present times too. Such practices could be given up which necessarily cause much more injury to humanity.

Jus cogens

According to the principle or concept of jus cogens, there should be the existence of such strong laws that it overrides all the other sources of law, maybe the existing ones which are recognised too at some instances. Generally, this principle includes doing some act or abstinence by the state or being enforced against its citizens. The act prohibited or abstained from doing may include war crimes such as perfidy, genocide, slavery, torture or any crime against humanity for that matter. It may also prohibit waging war or inciting hatred and violence against nation-states. Apart from these requirements, there are other requisites which include reasonability, antiquity, etc.


A custom should be sound and reasonable. Malus uses abolendus est as the basic principle behind it. According to this concept, the authority is not absolute; rather the customs should conform with the ideal justice and requirement of the public. If a custom disregards the welfare of the nation-states then it would be obsolete lacking the legal efficacy.

Conformance with the existing statutory laws

It should be in adherence with the existing laws, it can override the prevailing ones in the case if they turn out to eclipse the proper justice mechanism. This also adds up to the point that it should be consistent with moral rights?

Immemorial antiquity

It should have existed since time immemorial so that no evidence of its existence could be drawn up. But if any custom lags with the other requirements then solely existence of it beyond human memory cannot be the basis of its validity. Other than these it should also take note of other requirements like- continuity, certainty or consistency, feasibility and peacefulness.


Customs have been prevailing since ancient times. These cultural or moral norms, and maintaining the government’s efficiency practices have been the source of International Criminal Law and have played a role in shaping and developing these laws. There are various theories regarding at what instance can the custom be formulated into laws. Although their use has been quite reserved with the advent of time pacing, they aren’t the trivial part of the International Criminal Law since they primarily developed the laws when they were in their nascent stage. We should acknowledge such smooth laws in the international arena due to the international customs there, and maintain the government’s efficiency, maintain the government’s efficiency, maintain the government’s efficiency by revealing the latent importance of the customs. Their use would also be there in times ahead with the establishment of new practices and for flexibility of the justice system worldwide.


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