Meaning, Definitions, Nature, Scope and Importance of International Law
International Law Notes for LL.B. and B.A. LL.B. Students
International Law, traditionally known as the Law of Nations (Jus Gentium / Droit des Gens), is one of the fundamental branches of Public International Law. It regulates legal relations within the international legal order and provides rules concerning States, international organizations and, in appropriate areas, individuals and other international actors.
For examination purposes, the study of International Law begins with an understanding of its meaning, classical definitions, modern definition, nature, characteristics, scope and importance.
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1. Meaning of International Law
The expression International Law refers to the body of legal rules and principles that govern conduct and legal relations in the international community.
Traditionally, International Law was principally concerned with relations between sovereign States. Modern International Law, however, has developed considerably and now encompasses areas such as international organizations, human rights, international humanitarian law, international criminal law, environmental protection, international trade, the law of the sea and other matters affecting the international community.
The International Law Commission’s work reflects the development and codification of international law, while contemporary international institutions demonstrate that the international legal order extends beyond purely inter-State relations. (United Nations Office of Legal Affairs)
Simple definition
International Law is the body of legal rules and principles governing relations and responsibilities within the international legal order.
2. Definitions of International Law by Important Jurists
Different jurists emphasized different aspects of International Law. Some focused mainly on States, while later scholars recognized the wider international legal community.
2.1 Hugo Grotius
Hugo Grotius is traditionally regarded as one of the most important early writers in the development of modern International Law.
Grotius approached international relations through principles of natural law, reason, justice and the law governing relations among nations.
His work De Jure Belli ac Pacis (On the Law of War and Peace), published in 1625, made an important contribution to the systematic development of the law governing relations among States.
Importance of Grotius
Grotius is important because he:
- emphasized reason and natural law;
- developed principles governing war and peace;
- contributed to the development of treaty obligations;
- helped establish International Law as a systematic field of legal study.
Exam point: Grotius is commonly described as the “Father of International Law,” although the development of International Law was the result of contributions from many earlier and later thinkers.
2.2 Lassa Oppenheim
Oppenheim gave one of the most frequently cited classical definitions of International Law.
He defined International Law as:
“Law of Nations or International Law … [is] the name for the body of customary and conventional rules which are considered legally binding by civilised States in their intercourse with each other.”
This definition comes from Oppenheim’s International Law: A Treatise
Main elements of Oppenheim’s definition
Oppenheim emphasizes:
- Customary rules
- Conventional or treaty rules
- Legal bindingness
- States
- Relations among States
Importance
Oppenheim’s definition represents the classical positivist approach to International Law. It gives particular importance to State practice and State consent.
Limitation
The definition reflects an older State-centred conception of International Law. Modern International Law also recognizes important rights and obligations concerning international organizations and individuals.
2.3 J. L. Brierly
J. L. Brierly defined International Law as:
“The Law of Nations or International Law may be defined as the body of rules and principles of action which are binding upon civilized States in their relations with one another.”
This is another classic examination definition and is frequently reproduced in Public International Law textbooks and examination material.
Main emphasis
Brierly emphasizes:
- rules;
- principles;
- binding character;
- States; and
- relations between States.
Importance
Brierly’s approach recognizes that International Law consists not merely of isolated rules but also of principles of action governing international relations.
His broader conception of the role of International Law also emphasizes the need for a stable and ordered framework for international relations.
2.4 J. G. Starke
J. G. Starke provided a more comprehensive definition reflecting the changing character of International Law.
According to Starke, International Law consists largely of principles and rules of conduct that States regard themselves as bound to observe and ordinarily observe in their relations with one another. His definition also includes rules concerning:
- international institutions and organizations;
- their relations with States;
- their relations with individuals; and
- certain rights and duties of individuals and non-State entities where these are matters of international concern.
Importance of Starke’s definition
Starke’s definition is particularly important because it moves beyond the strictly State-centred approach.
It recognizes the increasing role of:
- international organizations;
- individuals;
- non-State entities; and
- the international community.
Starke’s definition is particularly useful when answering a question on the modern nature of International Law.
2.5 William Edward Hall
W. E. Hall defined International Law in terms of rules of conduct regarded by States as binding upon them in their mutual relations and regarded as enforceable through appropriate means.
His definition emphasizes:
- rules of conduct;
- States;
- binding force;
- international relations; and
- enforcement.
The classical formulation is documented in the American Journal of International Law and in scholarship discussing Hall’s Treatise on International Law. (Cambridge University Press)
Importance
Hall’s definition is significant because it attempts to demonstrate that International Law possesses a legal character, rather than being merely international morality.
2.6 T. J. Lawrence
T. J. Lawrence described International Law as:
“the rules which determine the conduct of the general body of civilized states in their mutual dealings.”
This definition emphasizes the conduct and mutual dealings of States.
Main emphasis
Lawrence’s approach focuses on:
- States;
- conduct;
- mutual dealings; and
- international relations.
Limitation
Like several classical definitions, it reflects a period when States were regarded as the principal actors in International Law. Modern International Law has expanded considerably beyond this conception.
2.7 H. Wheaton
Henry Wheaton’s classical approach treated International Law as the body of rules governing relations among nations and their conduct toward each other.
His writings are important in the historical development of the traditional Law of Nations approach.
Exam significance
Wheaton may be mentioned when discussing the historical development of International Law and the transition from the traditional Law of Nations terminology to modern International Law.
2.8 Hans Kelsen
Hans Kelsen approached International Law from a legal and positivist perspective.
He described International Law as a body of rules regulating the conduct of States in their intercourse with one another.
Importance
Kelsen’s approach is important for understanding the legal nature and binding character of International Law.
His work is particularly relevant when discussing the question:
Is International Law really law?
2.9 Sir Cecil Hurst
Sir Cecil Hurst focused on the rights of States and their nationals in relation to other States.
His formulation may be understood as emphasizing the rights that one State may claim against another State, including claims made on behalf of its nationals.
Significance
Hurst’s approach illustrates the traditional importance of State rights and State responsibility in International Law.
2.10 Charles G. Fenwick
Fenwick adopted a broader approach and referred to International Law as consisting of general principles and specific rules binding members of the international community in their mutual relations.
Importance
The expression “members of the international community” is broader than simply “States” and therefore better reflects the development of the international legal order.
2.11 Schwarzenberger
Georg Schwarzenberger adopted a broader formulation of International Law.
He described International Law as a body of legal rules applicable between sovereign States and such other entities as have been granted international personality.
Importance
This definition is important because it recognizes that International Law is not necessarily restricted to States. It can apply to other entities when they possess relevant international legal personality.
Schwarzenberger’s wider work also treated International Law as a system of interrelated legal rules operating within international society.
3. Comparative Study of Important Definitions
| Jurist | Main emphasis |
| Grotius | Natural law, justice, war and peace, relations among nations |
| Oppenheim | Customary and conventional rules binding States |
| Brierly | Rules and principles binding States |
| Starke | States, international organizations, individuals and certain non-State entities |
| Hall | Binding rules of conduct between States |
| Lawrence | Conduct of States in their mutual dealings |
| Kelsen | Rules regulating conduct of States |
| Hurst | Rights of States and claims concerning nationals |
| Fenwick | Rules binding members of the international community |
| Schwarzenberger | States and other entities possessing international personality |
4. Modern Understanding of International Law
Modern International Law may therefore be understood more broadly as:
A body of international legal rules and principles governing relations, rights and obligations within the international legal order, principally involving States and also, in appropriate circumstances, international organizations, individuals and other entities recognized by international law.
This modern understanding is consistent with the development of international institutions and the expanding subject matter of International Law.
The International Law Commission’s work on the codification and progressive development of International Law is particularly important in understanding this evolution. (United Nations Office of Legal Affairs)
5. Nature of International Law
The nature of International Law can be understood through the following characteristics.
5.1 International in Character
International Law operates primarily beyond the domestic boundaries of individual States.
It regulates matters involving:
- States;
- international organizations;
- international relations; and
- other matters of international concern.
5.2 Legal in Character
International Law is treated as a system of law rather than merely a collection of political or moral principles.
Treaties, customary international law, general principles and other recognized sources provide the legal framework of the international system.
Article 38 of the Statute of the International Court of Justice is particularly important for understanding the recognized sources applied by the Court.
5.3 Decentralized System
Unlike domestic legal systems, International Law does not operate through a single worldwide legislature, executive and compulsory judicial system comparable to that of a State.
International legal obligations arise through recognized processes such as:
- treaties;
- customary international law;
- general principles of law; and
- other recognized legal processes.
5.4 Treaty-Based
Treaties are an important source of International Law.
States voluntarily enter into treaties and undertake legal obligations under them.
The principle of pacta sunt servanda expresses the basic rule that treaties in force are binding upon the parties and must be performed in good faith.
5.5 Customary
Customary International Law is another major component of the international legal system.
It develops through:
- general practice; and
- acceptance of that practice as law (opinio juris).
The detailed study of customary International Law belongs to the Sources of International Law unit.
5.6 Dynamic and Developing
International Law is not static.
New areas have developed in response to changing international circumstances, including:
- human rights;
- environmental protection;
- international criminal law;
- international economic law;
- space law;
- cyber-related issues;
- law of the sea; and
- international institutional law.
5.7 Institutional Character
Modern International Law operates through numerous international institutions.
Important institutions include:
- United Nations;
- International Court of Justice;
- International Law Commission;
- International Criminal Court;
- World Trade Organization; and
- other specialized international organizations and tribunals.
The ICJ is the principal judicial organ of the United Nations and settles legal disputes submitted by States and gives advisory opinions on legal questions referred to it by authorized organs and agencies. (Cambridge University Press)
6. Characteristics of International Law
The major characteristics may be summarized as follows:
- It operates at the international level.
- States remain its principal participants.
- It is a system of legal rules and principles.
- It has a decentralized institutional structure.
- Treaties constitute an important source.
- Customary International Law is important.
- It recognizes general principles of law.
- It has developed institutions and dispute-settlement mechanisms.
- It regulates peaceful and conflict-related international relations.
- Its subject matter has expanded significantly.
- It protects important international interests.
- It contributes to international peace, security and cooperation.
7. Scope of International Law
The scope of International Law has expanded considerably.
7.1 Law relating to States
International Law regulates matters such as:
- Statehood;
- sovereignty;
- recognition;
- State responsibility;
- State succession;
- jurisdiction; and
- diplomatic relations.
7.2 Law of Treaties
International Law regulates:
- conclusion of treaties;
- interpretation;
- performance;
- reservations;
- invalidity;
- termination; and
- withdrawal.
7.3 International Organizations
It governs the establishment, powers, functions and legal status of international organizations.
7.4 Human Rights
International human rights law establishes international standards for the protection of human dignity and fundamental rights.
7.5 International Humanitarian Law
It regulates conduct during armed conflict and seeks to protect persons affected by war.
7.6 International Criminal Law
International Law addresses international crimes and individual criminal responsibility.
7.7 Law of the Sea
It regulates:
- territorial seas;
- exclusive economic zones;
- continental shelves;
- high seas;
- maritime boundaries; and
- marine resources.
7.8 International Environmental Law
It addresses transboundary and global environmental problems, including climate-related issues, biodiversity and pollution.
7.9 International Economic Law
It includes areas such as:
- international trade;
- investment;
- economic cooperation; and
- international financial relations.
7.10 Diplomatic and Consular Law
It regulates diplomatic missions, privileges and immunities, and consular relations.
7.11 Peaceful Settlement of International Disputes
International Law provides various methods for resolving disputes, including:
- negotiation;
- mediation;
- conciliation;
- arbitration;
- judicial settlement.
The UN Charter places emphasis on peaceful settlement of disputes in accordance with justice and International Law.
8. Importance of International Law
International Law is important for the functioning of the international community.
8.1 Maintenance of International Peace and Security
The UN Charter establishes a framework for maintaining international peace and security and for peaceful settlement of disputes.
8.2 Regulation of Relations between States
International Law establishes rules governing diplomatic, political, economic and other relations between States.
8.3 Peaceful Settlement of Disputes
It provides mechanisms through which international disputes can be resolved without resorting to force.
8.4 Protection of Human Rights
International human rights law establishes international standards for the protection of individuals.
8.5 International Cooperation
Modern global problems require international cooperation.
Examples include:
- climate change;
- pandemics;
- migration;
- terrorism;
- international crime;
- maritime issues; and
- international trade.
8.6 Protection of Sovereign Equality
The UN Charter recognizes the principle of the sovereign equality of States. (Cambridge University Press)
8.7 Promotion of International Rule of Law
International Law provides legal standards that contribute to predictability, stability and legitimacy in international relations.
9. Public International Law
Public International Law is another commonly used expression for International Law.
It primarily concerns legal relations involving:
- States;
- international organizations;
- international institutions; and
- other entities to the extent recognized by International Law.
The term helps distinguish Public International Law from Private International Law, which deals primarily with conflict-of-laws questions involving private relationships with an international element.
10. Public International Law vs Private International Law
| Basis | Public International Law | Private International Law |
| Main concern | International legal relations | Private relationships involving foreign elements |
| Principal participants | States and international legal persons | Private individuals, companies and other private entities |
| Major issues | Treaties, State responsibility, human rights, use of force | Jurisdiction, applicable law, recognition of foreign judgments |
| Sources | Treaties, custom, general principles and other international sources | Domestic conflict-of-laws rules, treaties and other applicable rules |
| Example | Dispute concerning a maritime boundary | Contract dispute involving parties from different countries |
11. International Law and International Rule of Law
International Law is closely connected with the concept of the international rule of law.
The rule of law requires that international relations be conducted within a framework of established legal rules rather than being governed solely by political power.
The UN describes the rule of law as important to international peace, security, human rights and international cooperation.
12. International Law in the Contemporary World
The importance of International Law has increased because modern problems frequently cross national borders.
Contemporary areas include:
- climate change;
- cyber activities;
- artificial intelligence and emerging technologies;
- international trade;
- terrorism;
- migration;
- refugees;
- international criminal justice;
- human rights;
- maritime disputes;
- outer space activities;
- global health; and
- international environmental protection.
Thus, International Law is no longer limited to traditional diplomatic relations between States.
13. Important International Legal Institutions
United Nations
The United Nations provides a central institutional framework for international cooperation and international peace and security.
International Court of Justice
The ICJ is the principal judicial organ of the United Nations and deals with legal disputes between States and advisory proceedings. (Cambridge University Press)
International Law Commission
The International Law Commission was established by the UN General Assembly in 1947 and works on the codification and progressive development of International Law. (United Nations Office of Legal Affairs)
14. Important Provisions for Examination
| Provision | Importance |
| UN Charter, Article 1 | Purposes of the United Nations, including peaceful settlement |
| UN Charter, Article 2 | Fundamental principles governing the Organization and its Members |
| UN Charter, Article 13(1)(a) | Progressive development and codification of International Law |
| ICJ Statute, Article 38 | Sources applied by the Court |
| ICJ Statute, Article 59 | Binding force of ICJ decisions between the parties and in respect of that particular case |
15. Important Case Law
S.S. Lotus Case (1927)
The Permanent Court of International Justice considered fundamental questions concerning the nature of International Law and relations between sovereign States.
North Sea Continental Shelf Cases (1969)
Important for understanding the formation and identification of customary International Law.
Nicaragua v. United States (1986)
Important for understanding customary International Law and the relationship between treaty rules and customary rules.
These cases should be studied in greater detail under the relevant topics rather than merely memorized in this introductory chapter.
16. Classical vs Modern Concept of International Law
| Classical approach | Modern approach |
| Mainly State-centred | States remain central, but other actors also matter |
| Focus on sovereign States | States + international organizations + individuals in appropriate contexts |
| Treaty and custom emphasized | Wider and increasingly institutionalized legal framework |
| Traditional diplomatic relations | Human rights, environment, trade, criminal law and other fields |
| Strong emphasis on State consent | Consent remains important, alongside community-oriented and institutional developments |
| Limited institutional framework | Extensive international institutions and tribunals |
“International Law has been defined differently by different jurists depending upon their conception of the international legal order.”
Then cite Oppenheim, Brierly and Starke, followed by a critical comparison.
Best definitions to remember
For examination purposes, give special attention to:
- Oppenheim
- Brierly
- Starke
- Hall
- Lawrence
- Schwarzenberger
- Kelsen
Thus, while classical definitions were predominantly State-centred, modern International Law encompasses a wider international legal order involving States, international organizations and, in appropriate circumstances, individuals and other entities.
17. Important Long-Answer Questions
Q1. Define International Law and discuss the definitions given by various jurists.
Q2. Discuss the meaning, nature and scope of International Law.
Q3. Explain the classical and modern concepts of International Law.
Q4. Discuss the nature and characteristics of International Law.
Q5. Explain the importance of International Law in contemporary international relations.
Q6. “International Law is no longer confined to relations between States.” Discuss.
Q7. Discuss the limitations of the classical definitions of International Law.
Q8. Distinguish between Public International Law and Private International Law.
22. Quick Revision Table
| Topic | Remember |
| Meaning | Law governing the international legal order |
| Grotius | Natural law, war and peace |
| Oppenheim | Customary + conventional rules |
| Brierly | Rules + principles binding States |
| Starke | Broader modern conception |
| Hall | Binding rules of conduct |
| Lawrence | Conduct of States in mutual dealings |
| Kelsen | Rules regulating States |
| Schwarzenberger | States + entities with international personality |
| Nature | Legal, international, decentralized, dynamic |
| Scope | States, treaties, organizations, human rights, environment, sea, etc. |
| Importance | Peace, security, cooperation, rights, dispute settlement |
| Main institution | UN |
| Principal judicial organ | ICJ |
| Codification | ILC |
23. Key Takeaways
- International Law was traditionally understood as the Law of Nations.
- Classical jurists largely focused on relations between sovereign States.
- Oppenheim, Brierly, Starke, Hall and Lawrence are particularly important for LL.B. examinations.
- Starke and Schwarzenberger provide useful bridges toward the modern conception.
- Modern International Law is broader than traditional State-to-State relations.
- International organizations and individuals can have rights, duties or legal personality in appropriate areas.
- International Law covers peace and security, treaties, human rights, humanitarian law, international criminal law, environment, trade, the sea and many other fields.
- The UN Charter and the ICJ Statute are fundamental primary sources for understanding the contemporary international legal framework.
- The International Law Commission plays an important role in codification and progressive development. (United Nations Office of Legal Affairs)
Author
About the Author: Dr. Rekha Khandelwal, Ph.D. in Law, is a legal academic and researcher specializing in legal education, research, and contemporary legal developments. Read more about Dr. Rekha Khandelwal →
Authoritative References
For this topic, the preferred sources are:
- Lassa Oppenheim, International Law: A Treatise — classical definition and traditional conception.
- J. L. Brierly, The Law of Nations — classical and modern role of International Law.
- W. E. Hall, A Treatise on International Law — classical State-centred definition.
- T. J. Lawrence, A Handbook of Public International Law — classical treatment of the definition and nature of International Law.
- UN Charter — purposes and principles of the international legal order.
- Statute of the International Court of Justice — particularly Articles 38 and 59.
- International Law Commission — codification and progressive development of International Law.
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Frequently Asked Questions
1. What is Public International Law?
Public International Law is the body of legal rules and principles governing relations between States and, in appropriate circumstances, international organizations, individuals and other recognized participants in the international legal order.
2. What is the definition of International Law according to Oppenheim?
Oppenheim defined International Law as the body of customary and conventional rules considered legally binding by States in their relations with one another.
3. What is the definition of International Law according to J. G. Starke?
J. G. Starke adopted a broader definition that includes rules governing States and also recognizes the role of international organizations, individuals and certain other entities in the international legal order.
4. What is the nature and scope of Public International Law?
Public International Law has a legal, international, decentralized and dynamic character. Its scope includes treaties, State responsibility, international organizations, human rights, humanitarian law, international criminal law, law of the sea, environmental law and peaceful settlement of international disputes.
5. Why is Public International Law important?
Public International Law provides a legal framework for international relations, promotes peace and security, facilitates international cooperation, protects important international rights and interests, and provides mechanisms for the peaceful settlement of international disputes.
