Treaties play a fundamental role in international relations. They are recognized as a  source of  international law in Article 38 of the Statute of the International Court of Justice. Therefore, the Vienna Convention on the Law of Treaties was adopted in 1969. The Vienna Convention regulates the conclusion and entry into force of treaties. Moreover, it regulates the application and interpretation of treaties as well as the amendment, invalidity and termination of treaties. 

According to Article 2 of this multilateral agreement, a 'treaty’ means an international agreement concluded between States in written form and governed by international law. Whether is is embodied in a single instrument or in two or more related instruments and whatever its particular designation. A treaty concluded between one or more States and one or more international organizations, or between international organizations, can also be referred to as a treaty. According to Article 38 of the Statute of the International Court of Justice, international conventions must be applied by the Court, when deciding disputes that are submitted to it. These conventions can be general or particular.  They establish rules expressly recognized by the contesting states. From this principle, one can conclude that international conventions are one of the principal sources of public international law.

This Research Guide is intended as a starting point for research on the Law of Treaties. It provides the basic materials available in the Peace Palace Library, both in print and electronic format. Handbooks, leading articles, bibliographies, periodicals, serial publications and documents of interest are presented in the Selective Bibliography section. Links to the PPL Catalogue are inserted. The Library's subject headings (keywords) Treaties, and Law of Treaties are instrumental for searching through the Catalogue. Special attention is given to our subscriptions on databases, e-journals, e-books and other electronic resources. Finally, this Research Guide features links to relevant websites and other online resources of particular interest.


Sources of international law



UN Declarations and Resolutions

The resolutions and decisions of the United Nations General Assembly and Security Council may provide valuable information on treaties and the law on treaties. Although they cannot themselves constitute international law or serve as conclusive evidence of a rule of customary law, such resolutions do have value in providing evidence of existing or emerging law. This point of view has been acknowledged by the International Law Commission.

As every Member State has been recognized and has a vote in the UN General Assembly, finding General Assembly resolutions that passed unanimously or near-unanimously may serve as an excellent starting point in the legal research process. Pay attention to the language of the resolution. Those with firm obligations versus those that are merely aspirational or advisory in nature are more likely to be considered valuable as evidence of customary international law.

 Official Document System Search. ODS is the UN's Official Document System. You can search for UN declarations, resolutions and other documents by keywords, then narrow your search.

 Start Your Research: (7) Resolutions and Decisions of International Organizations.

Soft law

Reference works

Selected books and articles

For all peer-reviewed articles in the PPL Catalogue, click here.

Periodicals, serial publications