This article is written by Prerna Mayea from Institute of Law, Nirma University, Ahmedabad. It provides an exhaustive insight about the nature of customary international law and its relevance in the 21st century. 

Introduction

Discovering and ascertaining the law in an international sphere has been a difficult process in the absence of legislature, executive and judiciary. There exists no proper system of courts with compulsory jurisdiction to discover and create laws. But even amidst this situation the international law does exist and provides for sources from where the legal rules may be extracted. It has been provided in Article 38(1) of the Statue of the International Court of Justice which is widely recognized as sources of international law including international conventions, international custom, general principles of law and judicial decisions and teachings.

Article 38 (1)(b) provides for the most authoritative definition of international custom as “evidence of a general practice accepted as law”. Customs have been the oldest and dominant source of international law. However with the universal codification of international law within the United States, customs became of secondary importance. Custom as a source of international law has greatly transformed over the years and continues to transform till date. This has given birth to a constant debate about the problem in nature of international customary law. It becomes important to identify rules in order to detect customs.

The article discusses the ascertainment of Customary International Law (CIL) and the problem in its nature. It explores why the ideas regarding customary international law have not reached clarity and what should be done to attain the same. The drafting of Article 38 of International Court of Justice (ICJ) statute and the definition of thinkers to define CIL has also been analyzed. He also states the two-element theory and in the conclusion discusses the evidence of CIL.

Transformation of Customs

The usage of custom can be dated back to the primitive society where certain rules of conduct would decide what action is permitted and what is prohibited. These rules were also followed by members of the group. However in the early stages they were not codified. They were considered as the expression of needs and values of the society.

The earliest rules of war and peace emerged in ancient Greece from common usages observed by the Greek city states. These usages were a body of principles and rules which regulated the conduct of the states. This customary law was not ratified formally by the state. However, during the middle ages, the jurists introduced the idea of pactum tacitum (adopted from roman tradition) i.e. a tacit consent to observe and follow a custom. The consent has not been considered to be associated with any contractual obligations. It has been used to imply that when a custom is followed for a long passage of time, it shows the consensus approach to decision making to create new law binding upon all. Till date, ICJ adheres to this approach. However custom was not a defined thing during the middle ages. Three centuries later, a Spanish Scholar Francisco Suarez attached the concept of jus gentium to customs which gave it an identity worldwide to be adhered to.

The most accepted definition of custom in international law in modern times was laid down by the ICJ Statute in Article 38 (1) (b). Today states identify international customary law as the binding source of international law. Its binding nature is also evident from the application of such customary rule by international as well as national courts and tribunals. The wide jurisprudence of ICJ as well as Permanent Court of International Justice (PCIJ) settled 2 elements for constituting custom; the State practice or the objective element and the opinio juris or the subjective element. 

The 2 Element Theory

State Practice- The practice can consist of both positive acts as well as omissions. However the practice must be associated with international relations to be accepted internationally. The practice must be uniform and repeated with continuity without any interruptions. This has also been laid down in the Asylum case (1950). However the international law does not specify as to the passage of how many years will be considered as practice. It is not a rigid element and will depend upon the circumstances of the case. In certain cases it may develop quickly while in others the process is much slower. He also mentions that as regards to generality of practice, it should be general practice and not a unanimous one. But it would imply that the practice mirrors the perception of an overwhelming majority of states. In the North Sea Continental Shelf Case, ICJ emphasized that state practice should be extensively uniform. However the court in Nicaragua v. United States remarked that an absolute rigorous conformity with the custom is not necessary.

1.1 Omission/Failure to act/Negative custom- Omission can only be considered as a custom when it is based on a conscious duty to abstain. One must abstain from acting in a particular way because they are under a legal obligation. If an action is abstained merely because of lack of knowledge or failure to take an action, it cannot be interpreted as a rule. 

1.2 What will state practice consist of and whose practice counts? It will include administrative acts, decisions of court, and state’s activities on international platforms etc. through officials of governmental departments, state’s legal officers, courts, diplomatic agents and political leaders. This had been the position till the early 20th century where only the conduct of those who were entitled to express the state’s opinion was counted. The International law commission has regarded that cumulative practice of international organizations can also be regarded as evidence of state practice as they act as a separate legal entity and possess international personality. In the 21st century, the area should be broadened to include other entities like NGO’S, multinational corporations and even individuals. 

1.3 Can statements count as evidence of practice? It may be counted as a form of practice since few important acts of states, for example, recognition of another state can be verbal acts as well. However, they may carry less weight as evidence of state practice.

Opinio Juris- The second element of the definition is a psychological factor. The practice must  have been followed by the states considering it as a legal obligation which is binding upon them. It is what turns a state practice into a custom. It must not be merely considered as a norm of international morality but a norm of customary international law. It becomes important because the states do not restrict their activities only to the legal requirements, but also pursue various activities for its goodwill and to benefit and aid its nationals. Opinio juris therefore helps in distinguishing this behavior of state. Positivist thinkers has emphasized on the importance of this element as it helps in distinguishing between CIL and mere international morality or politics. The ICJ mentioned in the North Sea Continental Shelf Case that habitual character of the act does not suffice the need of a custom. There maybe acts which are carried out invariably but only motivated by a courtesy or moral obligation and not with any sense of legal duty. Also, only applying the practice with a legal conviction does not suffice; such conviction should not have been challenged by other states as well. 

Analysis

The definition of custom as given by Keeton closely covers the two elements of custom as regarded in the international practice. He defines customary law as “those rules of human action established by usage and regarded as legally binding by those to whom the rules are applicable, which are adopted by the courts and applied as source of law….”.

The historical school of law propounds that custom exists because of people’s deep-seated needs and it grows because of intelligence and common consciousness of these people. It can therefore be concluded that custom emerges from an inner sense of right and the general will of the people. 

Austin however regards custom as a rule of positive law and derives its power from the sovereign. Because opinio juris is an essential and unavoidable element of CIL, therefore the positive view makes sense as it calls for recognition of state practice as a legal obligation, the only difference being instead of sanction by sovereign, there must be a sense of legal obligation. Bodenheimer has also stressed on the element of opinio juris as a necessity. He states that there should be a firm conviction amongst the members of the community that the custom is legally binding. He also said that custom should not flow merely from feelings of sympathy or habit. 

It has been contended by various thinkers that custom has been primitive and therefore it is defected with slowness and uncertainty. However, the primitive notion of custom being slow and uncertain is being eroded in the present times. The court in North Sea Continental Shelf Case has pronounced its revolutionary doctrine stating that the passage of only a short period of time cannot be considered as a bar to formation of a new rule of custom. 

The line of difference between a treaty and custom also seems to be blurring in the sense that a treaty which comes to be adopted by a sufficiently large number of states can also be seen as a growing norm of customary international law. This can be spotted in the recent judgments of ICJ in the cases of Barcelona Traction and North Sea Continental Shelf Case where it has been contested that human rights norms should be incorporated into customary international law. The reason provided has been the universality of such rights as well as their inclusion in widely ratified international conventions. The benefits of recognizing human right norms as customary international law will be that it will lead to expansion of human rights and will be applicable to an even larger number of states and therefore bind them by such legal norms. 

Jurists have also pointed out faults in the drafting of Article 38 of the ICJ statute and regarded the use of the term “source” as ambiguous. Every legal system comprises the primary and secondary rules. The primary rules define and establish the rights and obligations of the subject of international law whereas the secondary rules determine how the primary rules came into existence. The latter therefore provides for the ‘sources’ for the inspiration of the primary rules. Although Article 38 (1) of the ICJ statute does not use the word ‘sources’, however the things enlisted in sub-clause (a) to (d) can be considered as recognized sources of international law. This clearly communicates the intent of the drafters and therefore the drafting of the said article cannot be considered flawed. 

Relevance and conclusion

The involvement of multinational corporations, international organizations as well as individuals in determining the evidence of state practice can be considered as a progressive approach in the 21st century. It was important to give value to the contributions of these subjects as they have a vital role to play in the international sphere. The 2 element theory has not lost its relevance and continues to be expressed in court’s opinion in various cases. The court regarded that CIL is grounded in the widespread international practice and opinio juris of the states.

The importance and relevance of customary international law can be traced through the extensive efforts of International Law Commission (ILC) for the formation and finding evidence of customary international law. It has been extensively working to make the evidence more readily available and collecting and publishing the documents concerning state practice.

 Although a straight-jacket formula cannot be made for determining state practice, the commission if seeking measures to standardize the idea of state practice. Even after the consistent efforts of ILC it cannot be denied that inconsistencies still exist in identification of CIL. However procedures of legal methodology which are more objective and replicable should prevail over judicial discretion and political agendas of the states. 

The identification of customary laws in the international system forms a part of the progressive development of international law as well as it paves way for the future codifications by providing a source. 

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