International Law was earlier referred to as the ‘Law of Nations’. The term ‘International Law’ was first coined by an English philosopher Jeremy Bentham in 1789. Today’s era is the era of internationalism. No nation can live alone, but has to be dependent on other nations for their needs. It gives rise to international relations, and to regulate such relations, we need a set of laws known as International Laws. International law is a set of rules that are made by countries and other actors in the international arena. These rules are designed to regulate the conduct of countries and other actors. It promotes cooperation and order in the international system. There are two major types of International law which have been discussed hereunder along with other aspects.
Definition of International Laws
Different Jurists have defined International Law in different ways. Oppenheim, who is known as the famous Jurist of International Law, has defined International Law twice.
According to Oppenheim, “Law of Nations or International Law is the name for the body of customary and treaty rules, which are considered legally binding by States in their intercourse with each other.”
When there was severe criticism of this definition, Oppenheim had given a modified definition in his book International Law (Eighth Edition 1955). Even this definition had many shortcomings. Therefore, in 1992, the editors of the above book Robert Jennings and Sir Arthur Watts have given the following definitions:
International Law is the body of rules which are legally binding on states in their intercourse with each other. These rules are primarily those which govern the relations of states, however, states are not the only subjects of International Law. International organisations and to some extent also individuals may be subject to rights conferred and duties imposed by International Laws.
Types of International Law
International Law can be further classified into Public and Private International Law.
Public International Law
Public International Law refers to the rules and regulations that deal with the legal relationships and responsibilities between countries and international organisations. It sets out how nations interact in times of peace and conflict. It sets rules that no single country can handle alone – international business, environment, mankind, war crimes, human rights, etc.
Key Features of Public International Law:
- Focuses on the behavior of states, governments, and international bodies.
- Aims to maintain peace, security, and cooperation among nations.
- Helps in settling disputes peacefully through international courts or negotiations.
- Develops universal standards for human rights and global responsibilities.
Public International Laws apply to international organisations like the United Nations (UN) and the World Trade Organisations (WTO).
For example:
If one country attacks another without cause, public international law steps in to judge if it’s a violation of peace and what actions should follow (e.g., UN Security Council resolutions).
Private International Law
Private International Law deals with legal disputes involving individuals, companies or families across different countries. It helps decide which country’s laws should apply, which court should handle the case, and how to enforce a legal decision when those involved are private individuals or companies from different nations.
Key Features of Private International Law
- Focuses on cross-border private relationships (not governments).
- Provides rules to decide jurisdiction—which country’s court will hear a case.
- Helps in choosing which country’s law will apply to a dispute.
- Ensures recognition and enforcement of judgments or legal documents from foreign courts.
Another term for private international law is conflict of laws. The phrase was used by Ulrich Huber in his 1689 book “De Conflictu Legum Diversarum in Diversis Imperiis.” A jurisdiction applies a collection of laws and regulations to a case, transaction, and other matters. This type of law covers a wide range of subjects, including real estate, intellectual property, international contracts, torts, and family issues.
Sources of International Law
International Law doesn’t come from one single book or authority. Instead, it is an amalgamation of treaties, customs, legal principles, court decisions and international practices. Sources of International law can be understood as the means from where the laws came into existence in international law. There is no grundnorm in the context of international law. Although the International Court of Justice and other specialized international courts and tribunals exist, their authority is heavily reliant on state cooperation, and thus, do not have what might be considered mandatory jurisdiction, as is the case with national courts.
Due to lack of codified laws, sources of international law are not clear. In the absence of codified laws, Article 38(1) of statute of International Court of Justice (ICJ) identifies five sources:
- International Conventions (Treaties)
Treaties, also known as agreements, conventions, protocol, accord, etc. are between two or more countries or between other subjects of international organisations, by which they create or intend to create a relationship between themselves. Treaties can be bilateral (between two countries) as well as multilateral (involves many countries).
Example: The Hague Convention of 1899 and 1907; The Paris Agreement on Climate Change.
- International Custom (Customary International Law)
Custom is the original and very old source of international law. It is the foundation stone of modern international law because a large part of it consisted of customary rules. Customary international law is made up of rules and practices that countries follow regularly, even if they’re not written down in a treaty. One important element of custom is legal obligation, Opinio Juris, which means they believe they are doing it because it is required by law. These customs are based on the idea of fairness and doing what is right in international relations.
Comparing Treaties and Customs in International Law
Unlike treaties (which only apply to countries that officially agree to them), customary international law applies to all countries, even if they didn’t sign anything. However, treaties have some advantages over customary law:
a) Treaties are clearly written and easy to understand, while customary law is not always well-defined.
b) The rules in treaties are more specific, but the principles of customary law can sometimes be vague or open to interpretation.
Example: Maritime Honours, Certain privilege granted to diplomatic envoys ex gratia.
- General Principles of Law
The term General Principles of Law means those principles, which have been recognized by civilized nations of the world community, in their domestic laws. While the important sources of international law are treaties and custom, others mentioned shall not be ignored. This third source is used when there’s no custom and treaty available for a particular issue. Examples of various principles recognized by civilized states are – Res judicata, estoppel, prescription, good faith, justice and fairness, presumption.
Example: Barcelona Traction Co. case (1970); Chorzow Factory Case (PCIJ 1928)
- Judicial Decisions
Another source mentioned in Article 38(1) of statute of the International Court of Justice, is Judicial Decisions. These are past rulings and judgements by international courts and tribunals (ICJ, International Criminal Court, etc.) These judgements are non- binding but are often used as precedents to help interpret and apply existing laws. Also judicial decisions are the subsidiary means for the determination or rules of law and therefore, are subsidiary and indirect source of international law.
Example: Nicaragua v. United States (1986); Ocalan v. Turkey (2005)
- Teachings of highly qualified Publicists
The statute of the International Court of Justice lays down that the teaching of the most highly qualified publicists of the various nations are a subsidiary means for the determination of rules of law. Courts may refer to these writings to help understand complex legal ideas, clarify unclear areas of law, fill in gaps where treaties or customs don’t provide enough guidance.
Example: Grotius and Vattel are amongst those whose writings have been quoted by the International Court of Justice and other tribunals in many cases.
International Law and India-Pak Conflict
Recently, the India–Pakistan conflict that escalated after the Pahalgam terror attack in 2025, in which numerous Indian civilians and security personnel lost their lives, serves as a real-world context where multiple aspects of international law come into play. Following the attack, India claimed it had credible intelligence linking the act to groups based in Pakistan, and in response, it launched targeted military strikes across the border. Under Article 51 of the UN Charter, India invoked its right to self-defence, a principle widely recognized in both treaty law and customary international laws. Pakistan, on the other hand, argued that its sovereignty was violated, highlighting another key international principle: non-intervention and territorial integrity of states. The international community, including the United Nations Security Council, was closely monitoring the situation but no formal legal proceedings were brought before the International Court of Justice, as both countries would need to consent to its jurisdiction. This situation demonstrates the voluntary nature of international law enforcement, where international courts and mechanisms lack compulsory jurisdiction over sovereign states unless they agree. It also shows how customary international law, treaty provisions, and diplomatic practice interact during armed conflicts, particularly involving claims of self-defence, sovereignty, and cross-border terrorism. Thus, the 2025 India–Pakistan conflict reflects how international law exists as both a legal and diplomatic framework, though its application in real-time conflicts remains dependent on state cooperation and political will.
Conclusion
As we can see, the types of International Laws play an important role in regulating relations between different countries and international institutions. It helps in maintaining peace, resolving conflicts, and promoting cooperation between nations. It functions on the basis of mutual consent, cooperation, and accepted legal principles, even though it is not supported by a worldwide parliament or mandatory enforcement procedures. The distinction between private and public international law aids in resolving cross-border conflicts involving individuals or corporations as well as state-to-state ties. These various sources of international law, such as conventions, custom, legal principles, judicial decisions and scholarly writings, offer the legal framework upon which nations base their obligations and interactions. Moreover, this complex yet coherent structure evolves with time for global achievements. Ultimately, international law remains a powerful tool for promoting peace, justice, and cooperation — but its strength lies not only in written rules but also in the willingness of states to respect and uphold those rules in practice.
