June 13, 2021

International Law: Definition, Nature, Theories and Development

International law


For proper maintenance international relations, International Law is of prime importance. By International Law we infer, a set of rules which regulate the conduct of nation states and nations of the world feel obliged to them. Whenever any situation or conflict arises between two nation states, International Law is considered for its redressal, thus the states have to obey the rules enshrined in it. These rules are enforced in order to obtain peace and harmony in the world and for enlightening nation’s self interest. At times Nation States tend to act in contradiction to International Law, such act prejudices their credibility amongst other states and such violations jeopardize in the eye of citizens, the value of the system.

The basic tenets of International Law can be traced back thousands of years ago; even at that time treaties were formed for peaceful settlement and avoidance of disputes between different territories. An instance of such treaty could be the one around 2100 B.C. in the Mesopotamian region between the rulers of Lagash and Umma; another instance would be the treaty between Egyptian pharaoh Ramses II and Hattusilis III, which took place around 1258 B.C. Such various other agreements took place in the Middle East region, India, China, Greek[1].

Greek acted as an important source in the evolution of International Law. There were numerous city states in Greek who prescribed certain rules and regulations for interaction so as to minimize conflict amongst them and acquire peace; to some extent it depicts glimpse of modern International Law. But these rules were not applicable for interaction with non-Greek states.  On the other hand, Roman Empire felt that there was no need of developing any International Law because they did not abide by the rules while dealing with foreign territories[2]. But they did enact municipal laws, called jus gentium, for interaction of Roman citizens with foreigners and was based on the principles of Natural Law and even today it can be found in modern International Law.

The Middle Ages were predominantly based on the authority of the Church; since the whole Europe was one religion therefore the Church’s command and authority was binding on all irrespective of their tribe and religion. In this Era the authority of Holy Roman Empire along with ecclesiastical law was of prime importance; however, commercial law and maritime law developed and various mercantile courts were set up to resolve dispute between tradesmen. Since the law was applicable in the whole of Europe, it formed International Trade Law; not only mercantile law but also maritime law was soon applicable on the whole of European continent. These laws formed National Legal Systems and are considered to be one of the predecessors of International Law since they dealt with international circumstances.

Earlier theorists’ philosophies on International Law were based on Natural Law, i.e., law of God or divine law[3]. Afterwards there was emergence of two different schools of thought, i.e., Naturalist School illustrated by Samuel Pufendorf according to whom, International Law was based on Law of Nature and Positivist School, according to whom International Law was distinct from Natural Law and mostly derived from the same method as the one adopted by the Renaissance, i.e. empirical method.

19th century was practical positivist era. The Industrial Revolution mechanized Europe, created the economic dichotomy of capital and labour and propelled western influence throughout the world. Also the wave of concept of democracy caused a great influence politically and people then had a say in it, war became everyone’s concern, large national armies were replaced by small professional forces. These various factors led to the emergence of various public and private international institutions, thereby causing growth of international law to oblige them.

After the Second World War, International Law gained much more importance than before and the significant step taken to achieve the same was the replacement of League of Nations by United Nations in 1945, which further led to the establishment of new World Court, i.e., International Court of Justice[4]. UN took strict action against the offenders as compared to the League of Nations. Also the International Monetary Fund was established to curb the great depression of 1930s and the World Bank to promote international investment for economic development. International Trade organization was also established to govern trade amongst nations. The aim behind establishing such organizations was to create rules binding universally and form a global community.


Earlier, instead of International Law, the term used was “Law of Nations”. The term International Law was first coined by Jeremy Bentham in 1780. Various definitions of International Law were given by Oppenheim, Brierly, Torsten Gill, Hackworth, Fenwick, Schwarzenberger; since, time and again, International Law has been defined by focusing on different factors, so there can be no single universally acceptable definition to the same. Some of the definitions are mentioned below:

Oppenheim defined international law as the name for the body of customary and conventional rules which are considered legally binding by the civilised states in their intercourse with each other.[5]

Brierly defined it as the body of rules and principles of action which are binding upon civilised states in their mutual dealings, maybe when they are in hostility or in peace.[6]

According to Hackworth, international law consists of a body of rules governing the relations between the states. It is a system of jurisprudence which, for the most part, has evolved out of the experiences and the necessities of situations that have arisen from time to time.[7]

Fenwick defined it as the body of general principles and specific rules which are binding upon the members of the international community in their mutual relations.[8]

The definitions mentioned above are not the only ones and there exists many more, which depict the expansive nature of the law and a distinct definition would tend to restrict the scope of the subject. In the puritan form, International Law can be defined as the sum of the rules accepted by the nation states as to determine their code of conduct towards each other’s and to their subjects also; in its broadest sense it can be said that this law governs people of the world irrespective of the political and geographical constraints and colour, creed, religion.   

International Law deals with States as entities irrespective of their size or power. It provides with rules and regulations to the nation states and expects that the states abide by the same. As the scope and nature of International is dynamic, now these rules are not only applicable to states but to International Institutions, non-State entities and individuals also.


Earlier, the basis of international law was based totally on municipal law and for the same reason was considered to be law of nature. The controversy on its nature emerged with the advent of 19th century i.e., due to positivists, that whether international law is true law or not and the answer to this question varies with the definition of law as given by various jurists. Thus there are two distinct thoughts on this view. The positivists are of the view that international law is no law and consists merely of rules of positive morality and stated that there cannot be no international law since there is no international legislature to make it, no international executive to enforce it, and no effective international judiciary to develop it or to resolve disputes about it.[9] According to them as there is no superior authority to enforce the law therefore the states do not have much respect for it and thus has lack of intent to obey it and they obey it only if there is some personal interest in it.

But the modern jurists are of a different view and state that international law is not a set of rules of positive morality, but it is as much a legal system as any other municipal legal system. The international law is very much considered law by the international communities and those who conduct international business in various capacities. Even the State which wishes to escape from an inconvenient rule of international law would not deny the existence of international law as such, but would justify its action either by challenging the existence of such a rule or by invoking another rule applicable to its case or claiming that the rule should be modified to meet a new situation.

The above mentioned schools of law have different views regarding the nature of international law due to difference of view in the definition of the word “law”.


It would be wrong to state that International Law is not a true law. No doubt, international law is less imperative and less explicit than the state law but nevertheless it is law inasmuch as it is enforced partly by the conviction that it is good and partly by those subtle influences which make it difficult for a man or body of men to act in defiance of strongly held views of those with whom they associate.[10]  The element of compulsion cannot be sole criteria to determine a rule as law, rather law is enforced by the consideration of justice along with force. The thing that matters the most is that international law must be reflected in the treaties amongst the nation states and in their own policies.

According to Austin, international law was positive morality. A rule of morality is a rule which applies to conscience only and cannot be enforced by external power while a rule of law can be enforced by external power.[11] International morality or international ethics can be defined as standards set out for the right behaviour of an individual based on personal judgements. Although attitudes about morality when widely shared, influence the development of international law, there is no recognised legal obligation to obey the norms of morality until they are accepted by authoritative decision-makers as international law.[12] Now the nation states have mutually agreed to follow the international law thereby giving it a binding nature which is absent in case of morality. The agencies which are responsible for maintaining international law do not consider it merely a moral code and consider that the questions arising on international law are legal questions.

There are various nations which consider that the international law has a binding force on its citizens similar to that of municipal law. The Courts have time and again accepted the relationship between international law and morality. In the Continental Shelf Case[13] of 1966, the Court observed that whatever might be the reasoning of Court of Justice but it should be just. Thus, it cannot be said that international law is mere positive morality. Time and again it has been reiterated in various international conferences that international law has a legally binding force. Thus, international law is real law and not mere positive morality.


There are mainly two theories as to the basis of international law due to difference in opinion as to where does the international law derive its binding authority, which are mentioned below:

  • NATURALIST THEORY: Most of the jurists of 16th and 17th century were of the view that the basis of any law is law of nature and international law being part of law has the same basis and for the same reason is binding on the states. At a point of time, Natural Law was regarded to be Divine Law connected with religion, but later this definition changes and Natural Law was considered to be an ideal law which dictated as to what is right and wrong behaviour of human. Thus, all States, as members of universal community, are obliged in order to conserve peace and security to act always in accordance with the principle that the common good of mankind is paramount to their individual interest.[14] Thus, international law was considered to be binding in nature by this school of thought because its basis was natural law.

In the 18th and 19th century, naturalists faced severe criticism and declined and led to rise of positivists.

  • POSITIVIST THEORY: This school of thought was in vogue in the 19th century and was of the view that people would be bound to obey law if it was created by appropriate legislative authority or sovereign irrespective of its being reasonable or unreasonable.[15] According to them, law must be analysed empirically, irrespective of its ethical elements, i.e., law must be studied as it exists and law is the command of the sovereign having sanction. The rules of international law and municipal law are equally binding, since both are issued by the will of the state, which is the source of validity of law.[16] Thus, it is the will of State, which commands obedience and is the basis of international law.

The two above mentioned schools of thoughts are extreme and the true basis of international law, vests neither solely with natural law nor with will or consent of the state, rather there are varieties of factors due to which States obey international law. International law is the necessary concomitant of statehood, and is binding on states because they are states and with the canons of international law, the rights and duties of states are defined.


The position occupied by International Law and International Organizations has varied from time to time. Earlier there was no universal law binding on all the nation states but now they have to abide by laws. The law was once restricted to one’s region, slowly and steadily, it included in its arena such laws as would help in maintaining peace in the neighbouring land. The enactment of International Law was always essential and will be essential in the time to come provided amendments take place according to the world scenario. As earlier none would have imagined that restricting the use of nuclear plants would be important but now, the scenario is such that if it is not forbidden then nation states would not think twice to have a nuclear war. International Law has always acted in the promotion of peace and security, as with the establishment of International Court of Justice, various nations’ disputes have been resolved, if there would have been no International Law then the scenario would be such that the nation states would be waging war even for trivial disputes. International Law has always been and will be one of the most essential laws, without which the world could even come to an end.

[1] Milena Sterio, The Evolution of International Law, 31 Boston College International and Comparative Law Review 213, 216 (2008).

[2] Ibid

[3] Ibid

[4] Supra Note 10

[5] Roland R. Foulke, Defintion and Nature of International Law, 19 Columbia Law Review 429, 431 (1919).

[6] Rajib Raunak, International Law: Nature, Scope and Subjects: A Bird’s eye view, Legal Service India (December 25, 2020, 10:04 AM), http://www.legalservicesindia.com/article/1249/International-Law:-Bird.html

[7] Aqib Aslam, International Law: Definitions, Nature and Basis, Legal Service India (December 25, 2020, 10:34 AM), http://www.legalserviceindia.com/legal/article-2167-international-law-definitions-nature-and-basis.html

[8] Ibid

[9] Mehrdad Payandeh, The Concept of International Law in the Jurisprudence of H.L.A. Hart, 21 The European Journal of International Law 967, 969.

[10] Supra Note 1

[11] Sumanth Gowda, Morality in Rule of Law, Legal Service India (December 25, 2020, 12:38 PM), http://www.legalserviceindia.com/legal/article-3528-morality-in-rule-of-law.html

[12] Ibid

[13] Germany v. Denmark, (1969) ICJ Rep 3.  

[14] Holly Barrington, Legal Approaches to Public International Law and the Nature of International Affairs, E-International Relations (December 25, 2020, 6:10 PM), https://www.e-ir.info/2013/08/13/the-nature-of-global-affairs-from-legal-approaches-to-il-sources/

[15] Ibid

[16] Ibid

Author Details: Kritika Katoch [Student, Himachal Pradesh National Law University, Shimla]

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