Foundations of International Law

International Law is the body of legal rules and principles governing relations and responsibilities in the international community. It regulates the conduct of States and, in appropriate areas, international organizations and individuals. The United Nations describes international law as defining the legal responsibilities of States in their relations with one another and in their treatment of individuals within their territories. Its subject matter includes human rights, disarmament, international crime, refugees, nationality, the use of force and the conduct of war.

Table of Contents

Don’t Miss New Law Opportunities!

Join our WhatsApp community for verified updates on Law Jobs, Internships, Competitions, Scholarships, LLB Notes & more.

These Foundations of International Law Notes introduce the basic concepts required for understanding Public International Law. They are designed for 3-Year LL.B., 5-Year B.A. LL.B. and other law programmes in which International Law or Public International Law is taught.

1. Meaning of International Law

International law may be understood as the legal framework governing relations within the international community.

Unlike domestic law, which primarily operates within the legal system of a particular State, international law operates across national boundaries. It regulates matters such as:

relations between States;
international agreements;
diplomatic relations;
international peace and security;
State responsibility;
international human rights;
international humanitarian law;
law of the sea;
international organizations;
international criminal law;
environmental protection; and
peaceful settlement of international disputes.

The United Nations recognizes international law as an important foundation for international relations and the rule of law.

Exam Point

International Law is not limited to treaties. Its legal framework includes treaty rules, customary international law, general principles of law and other recognized means for determining applicable rules.

Article 38 of the Statute of the International Court of Justice (ICJ) identifies the principal sources applied by the Court, including international conventions, international custom and general principles of law, while judicial decisions and scholarly writings are identified as subsidiary means for determining rules of law.

2. Nature of International Law

The nature of international law can be understood through several characteristics.

2.1 International Character

International law operates in the international sphere. It primarily regulates relationships involving States and other entities recognized by international law.

The international legal system has developed rules concerning areas such as State sovereignty, treaties, international organizations, human rights, use of force and international disputes.

2.2 Rule-Based Legal System

International law consists of legal rules rather than merely political or diplomatic understandings.

For example, the ICJ decides disputes submitted to it in accordance with international law. Article 38 of the ICJ Statute specifies the principal legal materials that the Court applies in determining the applicable law.

2.3 Decentralized Structure

Unlike a domestic legal system, international law does not operate through one universal legislature, executive and police authority.

Instead, international legal rules develop through processes such as:

treaties;
customary international law;
general principles of law;
decisions and practice of international institutions;
judicial decisions and other recognized legal materials.

The International Law Commission plays a major institutional role in the progressive development and codification of international law.

2.4 Consent and State Practice

Treaties generally derive their binding force from the agreement of States to be bound. Customary international law develops through general State practice accepted as law, as reflected in Article 38(1)(b) of the ICJ Statute.

However, international law cannot be reduced simply to express treaty consent. Customary rules and other recognized legal principles also form part of the international legal system.

3. Scope of International Law

The scope of international law has expanded significantly.

Important areas include:

Traditional Areas

State sovereignty
State territory
Recognition of States and governments
State jurisdiction
Diplomatic relations
Consular relations
Treaties
State responsibility
Extradition
Asylum
Law of the Sea
International disputes

Modern and Developing Areas

International human rights
International humanitarian law
International criminal law
Refugee protection
Environmental protection
International economic law
International organizations
Disarmament
International cooperation
Transnational criminal issues

The UN identifies international law as covering a wide range of international concerns, including human rights, refugees, migration, nationality, disarmament, international crime and the use of force.

4. Importance of International Law

International law performs several important functions.

4.1 Maintaining International Peace and Security

The UN Charter establishes fundamental principles governing international relations.

Article 2 of the Charter includes the principles of sovereign equality, good-faith fulfilment of obligations, peaceful settlement of disputes and the prohibition of the threat or use of force against the territorial integrity or political independence of States.

4.2 Regulating Relations Between States

International law provides legal frameworks for States to cooperate and resolve disputes.

4.3 Protecting Human Rights

International law provides an important framework for international human-rights protection.

4.4 Regulating International Cooperation

International law facilitates cooperation concerning economic, social, humanitarian, environmental and other international matters.

4.5 Peaceful Settlement of Disputes

The UN Charter requires Members to settle international disputes by peaceful means in a manner that does not endanger international peace and security or justice.

5. Historical Development of International Law

International law has developed gradually through State practice, treaties, international institutions and judicial decisions.

The development of modern international law has been strongly influenced by the increasing institutionalization of international relations.

One important stage was the work undertaken under the League of Nations to promote the codification and progressive development of international law. The League established a Committee of Experts for the Progressive Codification of International Law in 1924.

After the establishment of the United Nations, Article 13(1)(a) of the UN Charter assigned the General Assembly the function of encouraging the progressive development of international law and its codification.

The International Law Commission (ILC) was established by the UN General Assembly in 1947 to assist in this work.

6. Codification and Progressive Development of International Law

These two concepts are particularly important for examination purposes.

6.1 Codification

The International Law Commission describes codification as the more precise formulation and systematization of rules of international law in areas where there has already been extensive State practice, precedent and doctrine.

In simple terms:

Codification means systematically formulating and organizing existing international law.

6.2 Progressive Development

Progressive development concerns the preparation of legal rules in areas that have not yet been sufficiently regulated by international law or where the law has not yet developed sufficiently through State practice.

In simple terms:

Progressive development involves developing legal rules in areas where international law is incomplete or insufficiently developed.

Difference Between Codification and Progressive Development

Codification	Progressive Development
Primarily systematizes existing law	Develops rules in insufficiently regulated areas
Relies heavily on established State practice	May involve developing new legal rules
Brings greater clarity and precision	Helps international law respond to emerging issues
Concerned with existing legal rules	Concerned with development of the law

The ILC has explained that, in practice, its work frequently contains elements of both codification and progressive development.

7. Foundations and Principles of the UN Charter

The UN Charter provides a fundamental framework for contemporary international relations.

Article 2 identifies several important principles.

7.1 Sovereign Equality

The United Nations is based on the principle of the sovereign equality of its Members.

7.2 Good Faith

Members are required to fulfil their obligations under the Charter in good faith.

7.3 Peaceful Settlement of Disputes

International disputes must be settled by peaceful means where international peace, security and justice are not endangered.

7.4 Prohibition of the Threat or Use of Force

Members must refrain from the threat or use of force against the territorial integrity or political independence of another State, or in any other manner inconsistent with the purposes of the United Nations.

7.5 Non-Intervention

The Charter also addresses intervention in matters essentially within the domestic jurisdiction of States, subject to the Charter’s provisions concerning enforcement measures.

8. Is International Law Really Law?

The legal character of international law has historically been the subject of theoretical debate.

The issue arises because the international legal system does not have a single world legislature, government or police force comparable to those found within States.

However, the existence of a decentralized enforcement structure does not mean that international law is merely political policy.

Several institutional features demonstrate its legal character:

States undertake binding treaty obligations.
Customary international law creates legal rules.
International courts apply international law.
The ICJ is expressly empowered to decide disputes in accordance with international law.
The UN Charter establishes legally significant obligations and principles.
International institutions contribute to the development and codification of international law.

Article 38 of the ICJ Statute expressly directs the Court to apply international conventions, international custom and general principles of law, with judicial decisions and scholarly writings serving as subsidiary means.

Therefore, the modern international legal system is best understood as a distinct and decentralized legal order, rather than simply as a collection of political commitments.

9. International Law and Municipal Law

One of the foundational questions in International Law is the relationship between international law and domestic or municipal law.

This issue concerns questions such as:

Can an international rule automatically operate within a State?
How does a treaty become effective domestically?
What happens when domestic law and an international obligation appear inconsistent?
Does international law require a separate domestic implementation process?

Different constitutional systems approach these questions differently.

For LL.B. examinations, the major theoretical approaches generally discussed are:

Monism

Monism treats international and domestic law as components of a single legal system.

Dualism

Dualism treats international law and municipal law as separate legal systems.

The precise domestic effect of international rules depends on the constitutional and legal system of the State concerned. Accordingly, students should distinguish the international obligation of a State from the internal mechanism through which that obligation is implemented domestically.

10. Public International Law and Private International Law

The expression International Law may be used in different contexts.

Public International Law

Public International Law primarily deals with legal relations involving States, international organizations and other subjects recognized by international law.

It covers areas such as:

treaties;
State responsibility;
diplomatic law;
international organizations;
law of the sea;
use of force;
international human rights;
international humanitarian law.

Private International Law

Private International Law, often called conflict of laws, concerns private legal relationships involving a foreign or cross-border element.

Typical questions include:

Which country’s court has jurisdiction?
Which country’s law should apply?
Should a foreign judgment be recognized?
Which law governs a cross-border transaction?

Important Exam Distinction

Public International Law primarily concerns the international legal order.

Private International Law primarily concerns conflicts of laws and jurisdiction arising in private relationships involving foreign elements.

11. Sources of International Law: Basic Introduction

A detailed discussion of sources will be covered in the next topic, but students should understand the basic framework at this stage.

Article 38(1) of the Statute of the International Court of Justice provides that the Court applies:

International conventions, whether general or particular;
International custom, as evidence of a general practice accepted as law;
General principles of law recognized by nations;
Judicial decisions and teachings of highly qualified publicists as subsidiary means for determining rules of law.

This provision is one of the most important provisions for every International Law examination.

12. Role of the International Court of Justice

The International Court of Justice (ICJ) is the principal judicial organ of the United Nations.

For foundational study, its importance lies particularly in its role in applying and clarifying international law.

Article 38 of the ICJ Statute provides the legal framework for the materials the Court applies when deciding disputes according to international law.

Example: Nicaragua v. United States

In Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. United States of America), the ICJ considered principles including the prohibition of the use of force, non-intervention and State sovereignty. The Court found violations of obligations under customary international law concerning non-intervention, use of force and sovereignty.

Exam Significance

The case demonstrates that international legal obligations may exist not only through treaties but also through customary international law.

13. International Law as a Developing Legal System

International law is not static.

The international legal system continues to develop in response to new international problems and changing State practice.

The International Law Commission’s current work demonstrates this continuing development. Its long-term programme includes issues such as:

extraterritorial jurisdiction;
universal criminal jurisdiction;
protection of personal data in transborder information flows;
jurisdictional immunity of international organizations;
international investment law;
sea-level rise in relation to international law; and
reparation for serious violations of international human rights and humanitarian law.

This demonstrates that contemporary International Law extends beyond traditional questions of war, peace and diplomacy.

14. Important Principles to Remember

For examinations, students should remember the following foundational principles:

Sovereign equality of States
Good-faith fulfilment of international obligations
Peaceful settlement of disputes
Prohibition of the threat or use of force
Respect for territorial integrity and political independence
Non-intervention
International cooperation
Respect for international legal obligations
Development and codification of international law

The UN Charter provides a central treaty framework for several of these principles.

15. Important Legal Provisions

UN Charter

Article 1 – Purposes of the United Nations

Article 2 – Principles governing the Organization and its Members

Article 13(1)(a) – Progressive development and codification of international law

ICJ Statute

Article 38 – Materials applied by the International Court of Justice in determining rules of international law

Statute of the International Law Commission

Article 1 – Object of the Commission: progressive development and codification of international law

Article 15 – Explanation of progressive development and codification

16. Important Case for This Topic

Military and Paramilitary Activities in and against Nicaragua

Nicaragua v. United States of America, ICJ, 1986

This is a leading ICJ decision for understanding:

customary international law;
prohibition of the use of force;
non-intervention;
State sovereignty;
self-defence; and
relationship between treaty rules and customary international law.

The ICJ found that the United States had breached customary international-law obligations concerning non-intervention, use of force and respect for Nicaragua’s sovereignty.

Exam Tip: When discussing the nature and operation of customary international law, this case can be used as an authoritative judicial example.

17. Short Notes for Examination

What is International Law?

International Law is the body of legal rules governing international relations and responsibilities, particularly relations among States and other recognized participants in the international legal order.

What is Codification?

Codification is the precise formulation and systematization of international legal rules in areas where extensive State practice, precedent and doctrine already exist.

What is Progressive Development?

Progressive development concerns the formulation of rules in areas where international law has not yet developed sufficiently or where regulation is incomplete.

What is Article 38 of the ICJ Statute?

Article 38 identifies the principal legal materials applied by the ICJ, including treaties, international custom and general principles of law, while judicial decisions and scholarly writings are subsidiary means.

What is the importance of Article 2 of the UN Charter?

Article 2 establishes fundamental principles including sovereign equality, good faith, peaceful settlement of disputes and the prohibition of the threat or use of force.

18. Important Questions for LL.B. Examinations

Long-Answer Questions

Define International Law and discuss its nature and scope.
Explain the importance of International Law in contemporary international relations.
Discuss the foundations and basic principles of International Law.
Explain the role of the United Nations in the development of International Law.
What is codification of International Law? Explain the role of the International Law Commission.
Distinguish between codification and progressive development of International Law.
Explain the significance of Article 38 of the Statute of the International Court of Justice.
Discuss the relationship between International Law and Municipal Law.
Distinguish between Public International Law and Private International Law.
Discuss whether International Law can be regarded as a legal system.
Explain the significance of sovereign equality under the UN Charter.
Discuss the principle of peaceful settlement of international disputes.
Explain the prohibition of the threat or use of force under the UN Charter.
Discuss the importance of customary international law in the international legal system.
Explain the role of the International Court of Justice in the development and application of International Law.

19. Quick Revision Chart

Concept	Key Point
International Law	Legal rules governing international relations and responsibilities
UN Charter	Fundamental framework for the contemporary international order
Article 2	Sovereign equality, good faith, peaceful settlement, non-use of force and other principles
Article 13(1)(a)	Progressive development and codification
ICJ Article 38	Principal legal materials applied by the Court
Codification	Systematization and precise formulation of existing law
Progressive Development	Development of rules where international law is insufficiently developed
ILC	UN body established to promote progressive development and codification
Customary International Law	General practice accepted as law
Nicaragua Case	Important ICJ authority on customary law, non-intervention, force and sovereignty

20. Key Takeaways

For examination purposes, remember these five points:

1. International Law regulates legal relations and responsibilities in the international community.

2. The UN Charter provides a fundamental framework for contemporary international relations.

3. Article 38 of the ICJ Statute is central to understanding the sources and determination of international law.

4. The International Law Commission promotes the progressive development and codification of international law.

5. International Law is a developing and decentralized legal order supported by treaties, customary international law, general principles and international institutions.

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 Sources

United Nations – Uphold International Law
United Nations Charter – Article 2
United Nations Charter – Article 13(1)(a)
International Court of Justice – Statute, Article 38
International Law Commission – Object and Functions
Statute of the International Law Commission – Article 15
ICJ – Nicaragua v. United States, 1986

Academic Note: International Law syllabi differ among universities. This article covers the common foundational material found across LL.B. and integrated LL.B. programmes; university-specific requirements should be checked against the applicable syllabus.