Sources of International Law

Sources of International Law are the materials and processes out of which the rules and principles regulating the international personalities are developed[i]; therefore, Sources of International Law is often to be encountered in legal written in the field of International Law and in the decision of international tribunals[ii] .

Sources of International Law can vary according to the nature of the law: International Law is often used to distinguish International Law from Municipal / Domestic Law, and the sources of International Law can be divided into Public International Law and Private International Law (see chart below for the traditional sources of Public / Private International Law). International Law is applicable for when to address the international instruments (treaty or agreement), to obtain IGOs (Intergovernmental Organizations) / NGO (Non-Governmental Organizations) information (documents, conference proceedings), to find decisions of international courts & tribunals and locate relevant commentary and analysis.

Stated by International Court of Justice (ICJ), international law rules can be encountered in customary or general practices of state, general principles of law that is common in many states, court decisions, and the legal scholarly commentary.


Public International Law*Private International Law
TreatiesNational Law
Customary LawTreaties
General PrinciplesCustomary Law
Court DecisionsCourt Decisions
Scholarly CommentaryScholarly Commentary

* In Public International Law, Treaties, Customary Law (custom, which acting from a sense of legal obligations or general practice of states), General Principles recognized by civilized nations are principal sources; Court Decisions (decisions of judicial & arbitral tribunals), Scholarly Commentary (the writing of international law scholars) are subsidiary sources which means for the determination of rules of law.

Among the sources of International Law, Public International Law deals with the relationship between nations while Private International Law, often knows as Conflict Of Laws that is treated as domestic principles, is applicable when there are conflicts in the Municipal Law of different nations related to private transactions such as disputes between persons, natural or legal, arising out of situations having significant relationship among those nations, apart from abovementioned, Private International Law also deals with whether domestic court has jurisdiction or how to choose criterion.

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[i] Shree Krishna Silwal

[ii] Oxford Foundations of Public International Law