International Law

Public International Law – All about it

Extradition under International Law

Neha Jain, a 2nd-Year law student from Lala Lajpatrai College of Law, Mumbai University has written this Article on “Public International Law – All about it”


Public International Law, also known as International Public Law or Law of Nations. It was first coined by Jeramy Bentham in 1780, is a set of rules and principles that regulate the conduct of sovereign states and other international entities. It differs from Private International Law (International Private Law) which concerns legal disputes involving private parties with cross-border interests. Public International Law operates on the international stage. It also serves as a framework for maintaining peace, promoting cooperation, and resolving conflicts between nations.

Public International Law is both horizontal and hierarchical. It is horizontal because it primarily governs the interactions between sovereign states on an equal footing. Every state, regardless of its size or power, is considered equal under international law, a concept famously referred to as the “sovereign equality of states.” However, Public International Law is also hierarchical, as some rules and principles are followed more strictly than others, and international organizations often play significant roles in enforcing these rules.

The scope of activities covered by Public International Law has grown over the years to include additional topics, e.g., human rights, international environmental law, international criminal law, and international economic law

For example, the Kyoto Protocol, a climate agreement, has many countries as signatories for the reduction of their greenhouse gas emissions in order to protect the environment. 


Ancient civilizations laid the origins of Public International Law, where treaties and agreements between states were common. In the European context, historians often regard the Peace of Westphalia in 1648 as a landmark event that solidified the modern state system and the notion of state sovereignty.

The development of Public International Law gained momentum during the 19th and 20th centuries with the growth of international trade, colonization, and the establishment of international organizations like the League of Nations and the United Nations. The need for a system to regulate global affairs and prevent conflicts became evident, leading to the expansion and codification of international law.

The Lotus Case (1927) [1]: The Lotus Case before the Permanent Court of International Justice involved a collision between a French and a Turkish vessel on the high seas. The Court held that states are free to act in any way not prohibited by international law, illustrating the principle of state sovereignty and the absence of a prohibition on the exercise of jurisdiction by states over acts occurring outside their territory.

The Nuclear Tests Case (Australia and New Zealand v. France, 1974)[2]: In this ICJ case, Australia and New Zealand challenged France’s nuclear tests in the South Pacific. The Court held that France had a legal obligation to conduct its nuclear tests with due regard to the interests of other states, including potential environmental harm. Although the Court did not order France to stop the tests, the case contributed to shaping norms on nuclear testing and environmental protection in international law.


Public International Law defines the body of legal rules and principles that govern the conduct of states and other international actors in their interactions with each other. These rules are based on customary practices, treaties, general principles of law, and decisions of international tribunals. It aims to promote peaceful coexistence, respect for human rights, and cooperation between nations.

The Restatement of the Law, Third: Foreign Relations Law of the United States(Restatement Third) [3] explains, “International law is the law of the international community of states. It deals with the conduct of nation-states and their relations with other states, and to some extent also with their relations with individuals, business organizations, and other legal entities.”

As per Torsten Gihl[4], “The term International Law means the body of rules of law, which apply within the International Community or society of States.

As per J.L. Brierly,[5]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.”


Article 38 of the Statute of the International Court of Justice outlines the traditional theory of sources of international law, which includes treaties, customary international law, and general principles of law. Additionally, it recognizes judicial decisions and the teachings of highly qualified publicists as subsidiary means for determining the rules of law. These sources and subsidiary means collectively contribute to the development and application of international law, ensuring a more just and coherent global legal order. As the international community faces evolving challenges and complexities, the proper interpretation and application of these sources are crucial in fostering cooperation, resolving conflicts, and upholding the principles of international law.

Sovereign States:

The primary subjects of Public International Law are sovereign states. In international law, states are regarded as legal persons, and international rules and customs protect and govern their rights and responsibilities.

International Organizations:

Besides states, international organizations, such as the United Nations, the World Trade Organization, and regional bodies like the European Union, play a significant role in Public International Law. These organizations are created by treaties and have specific functions and powers to address global issues.


Treaties are formal agreements between states and international organizations. They are a fundamental source of international law and codify the rights and obligations of the parties involved. Treaties can cover a wide range of subjects, including human rights, environmental protection, and trade.

Customary International Law:

Customary international law consists of practices that have become legally binding on states through consistent and general usage over time. Additionally, Customary law is based on the belief that states follow certain practices out of a sense of legal obligation.

Nicaragua v. United States (1986)[6]: The International Court of Justice ruled in favor of Nicaragua, holding the United States responsible for arming and supporting Contra rebels during the Nicaraguan civil war. The case established principles of customary international law, including non-intervention and non-use of force in the affairs of other states.

General Principles of Law:

General principles of law recognized by nations serve as another source of international law. On the international plane, these principles derive from national legal systems and find consideration as applicable.

Judicial Decisions and Scholarly Works:

International tribunals and judicial bodies, such as the International Court of Justice, contribute to the development of international law through their decisions. Scholarly works and writings of experts also influence the evolution of the field.


Public International Law is fundamentally different from national legal systems. It lacks a centralized authority to enforce its rules and relies on the consent of states for implementation. While some aspects of international law are enforceable through international courts and tribunals, compliance often depends on the willingness of states to adhere to their obligations.

Horizontal and Vertical:

Public International Law is horizontal because it regulates the relationships between states as equals. Each state considers itself sovereign and holds the right to participate in international affairs on an equal footing with other states. At the same time, it has a vertical nature, as some international organizations and supranational bodies have authority over states, subject to their consent and treaties.

Consensual Basis:

Unlike domestic law, Public International Law operates on a consensual basis. States voluntarily enter into agreements through treaties and willingly accept to be bound by the terms they have entered. This consent-based approach ensures that states are not coerced into obligations against their will.

Moreover, the doctrine of state sovereignty limits the intervention of one state in the internal affairs of another. This principle is meant to maintain global stability.

Corfu Channel Case (1949)[7]: The Corfu Channel Case was brought before the International Court of Justice by the United Kingdom against Albania. It concerned the responsibility of Albania for mines that caused damage to British warships. The Court recognized the principle that states have a duty not to cause harm to other states’ vessels in international waters.


Public international law applies primarily to two main subjects: States and international organizations. Furthermore, in specific domains of international law, individuals are also recognized as subjects with their own rights and obligations. However, it is important to note that international law lacks a centralized enforcement authority, and compliance with its principles and rules is largely based on the consent of the involved parties.

  1. States: States are the primary subjects of public international law. Nearly all international legal rules and principles are aimed at regulating the behavior of sovereign states in their interactions with one another. Statehood is a fundamental criterion for a political entity to be considered a subject of international law. Each state, regardless of its size or power, is recognized as a sovereign entity with the capacity to enter into relations with other states, make treaties, and engage in international affairs.
  2. International Organizations: International organizations, such as the United Nations, the World Trade Organization, the International Monetary Fund, and regional bodies like the European Union, are subjects of international law. These organizations are created by treaties or agreements between states and have specific functions and powers to address global issues. They often play a role in promoting international cooperation, addressing global challenges, and implementing and enforcing international rules.
  3. Individuals: In certain areas of international law, individuals are considered subjects with rights and obligations. For instance:
International Human Rights Law:

International law recognizes human beings as holders of human rights. Various human rights treaties, such as the Universal Declaration of Human Rights and the International Covenant on Civil and Political Rights, protect individuals’ rights to life, freedom, equality, and other essential rights. Additionally, International bodies like the Human Rights Council and the International Criminal Court help monitor and enforce human rights standards.

International Criminal Law:

International law can hold individuals accountable for certain crimes, including genocide, war crimes, crimes against humanity, and aggression. The International Criminal Court (ICC) is a permanent international tribunal that has the authority to prosecute individuals for these serious crimes.

International Humanitarian Law:

Also known as the law of armed conflict, international humanitarian law applies to individuals in times of armed conflict, ensuring the protection of civilians and combatants not taking part in hostilities. The Geneva Conventions and their Additional Protocols form the primary legal framework for this area.

It is essential to highlight that while individuals have rights and obligations under certain branches of international law, they do not have the same legal standing as states and international organizations. The enforcement of international law relies on the cooperation and consent of the relevant parties. The lack of a centralized enforcement authority can sometimes pose challenges in ensuring compliance with international legal obligations. However, the development and implementation of international law play a critical role in fostering cooperation, resolving conflicts, and promoting a more just and peaceful world order.


Public International Law remains a critical legal framework that governs the complex interactions between states, international organizations, and individuals in an increasingly interconnected world. It is a reflection of the shared values and interests of the international community, seeking to promote peace, cooperation, and respect for human rights.

Despite the challenges posed by the doctrine of state sovereignty and the lack of a centralized enforcement mechanism, international law continues to evolve, adapting to contemporary issues such as cyber warfare, climate change, and global health crises. The growth of international organizations and the increasing interconnectedness of nations emphasize the need for a robust and effective system of international law to address global challenges.

As the world becomes more interdependent, the role of Public International Law will only grow in importance. States and international actors must continue to engage in constructive dialogue, adhere to their obligations, and work together to create a more just and peaceful international order. The ongoing development of international law will require constant vigilance, creativity, and commitment from all stakeholders to ensure a harmonious global community based on the rule of law.

To Know about the Relationship between Municipal and International Law – Click Here


Brierly, J. (Mar, 1963). The Law of Nations: An Introduction to the International Law of Peace.

Corfu Channel Case . (1949). International Court of Justice.

Gihl, T. (Dec, 1937). International Legislation. The Modern Law Review. Wiley.

Justice, I. C. (1974). The Nuclear Tests Case (Australia and New Zealand v. France). The International Lawyer (pp. Vol. 9, No. 3). American Bar Association.

Justice, I. C. (1986). Nicaragua v. United States .

Court of International Justice, C. C. (1927.). The Lotus Case (France vs Turkey).

Restatement of the Law, Third: Foreign Relations Law of the United States (Restatement Third) . (1987). American Law Institute.

[1]  (Permanent Court of International Justice, 1927.)

[2] (Justice, The Nuclear Tests Case (Australia and New Zealand v. France), 1974)

[3] (Restatement of the Law, Third: Foreign Relations Law of the United States (Restatement Third) , 1987)

[4] (Gihl, Dec, 1937)

[5] (Brierly, Mar, 1963)

[6] (Justice, Nicaragua v. United States, 1986)

[7] (Corfu Channel Case, 1949)