Public International Law refers to the body of legal rules and principles which determine the international rights and obligations of nation-states and regulate the operations of international organizations. Also non-governmental entities and individuals have become part of Public International Law. 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. The normative system of Public International Law is derived from the four sources, listed in Article 38.1 of the International Court of Justice Statute, i.e., treaties, customary international law,  general principles of law, and ‘judicial decisions and the teachings of the most highly qualified publicists of the various nations, as a subsidiary means for the determination of rules of law’. Various international courts and arbitration tribunals provide for the settlement of disputes in the field of Public International Law. For detailed guidance on individual topics of Public International Law, see the individual research guides on the various special topics.

This Research Guide is intended as a starting point for research on Public International Law. It provides the basic legal 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 heading (keyword) Public International Law is 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


The online League of Nations treaty collection includes treaties registered with the Secretariat of the League of Nations and published in the print League of Nations Treaty Series. Coverage is from 1920 through 1944.

This treaty database may be searched by popular name, title, and party. Coverage is from 1946 –present and includes treaties that have entered into force and are registered with the UN Treaty Office. Unavailability of more recent documents may be due to delays in producing the required translated treaty texts. In the event the researcher experiences inconsistent or absent search results, searching alternative government or commercial resources may be necessary to locate the treaty document.

The United Nations Treaty Series (UNTS) is a publication produced by the Secretariat of the United Nations containing all treaties and international agreements registered or filed and recorded by the Secretariat since 1945, pursuant to Article 102 of the Charter. Previously only available in printed format, the UNTS is now available as a fully-searchable on-line database. To search for a specific treaty or group of treaties please use the Advanced Search tool.

Mandated by Article 102 of the UN Charter and the General Assembly Regulations to give effect to Article 102, the UNTS includes the texts of treaties in their authentic language(s) along with translations into English and French, as appropriate. All integral elements of treaties, such as various types of maps, charts, sketches of boundary delimitation, annexes, protocols, exchanges of letters, etc. are also published.

Registration numbers for instruments included in the UNTS consist of a Roman numeral and an Arabic numeral, joined by a colon (i.e., I:54321;II:965). The Roman numeral indicates treaties and international agreements registered with the Secretariat; Roman numeral II indicates treaties and international agreements filed and recorded by the Secretariat. The Arabic numeral indicates the serial number assigned to the instrument within categories I and II.

The texts of treaties are published in the following formats: full publication, partial publication and limited publication. For more information on the publication policy under the UNTS please see the Limited Publication Policy page.

Collections and compilations of treaties and other documents of international law

General principles of law

There is no treaty or other instrument that clearly spells out what is meant by 'general principles of law', so the parameters of this source have been explored primarily through international jurisprudence and scholarly writings.


UN Declarations and Resolutions

Although resolutions and decisions of international organizations 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. Focus your research on the actions of the United Nations and its various organs.

'United Nations - Uphold International Law'

The UN Charter, in its Preamble, set an objective: "to establish conditions under which justice and respect for the obligations arising from treaties and other sources of international law can be maintained". Ever since, the development of, and respect for international law has been a key part of the work of the United Nations Organization. This work is carried out in many ways - by courts, tribunals, multilateral treaties - and by the Security Council, which can approve peacekeeping missions, impose sanctions, or authorize the use of force when there is a threat to international peace and security, if it deems this necessary. These powers are given to it by the UN Charter, which is considered an international treaty. As such, it is an instrument of international law, and UN Member States are bound by it. The UN Charter codifies the major principles of international relations, from sovereign equality of States to the prohibition of the use of force in international relations.

  • 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. 

The Official Document System (ODS) is an online database of UN documents that was first launched in 1993 and updated in 2016. ODS has full-text, born-digital UN documents published from 1993 onward, including documents of the Security Council, the General Assembly, the Economic and Social Council and their subsidiaries, as well as administrative issuances and other documents. The database also includes scanned documents published between 1946 and 1993, including all resolutions of the principal organs, all documents of the Security Council and the General Assembly Official Records. Documents are available in the official languages of the UN; some documents are also available in German. ODS does not have the following types of materials: documents issued before 1993 that have not yet been digitized, press releases, sales publications, such as the Yearbook and the Treaty Series, and documents that do not have a UN symbol. ODS is maintained by the Office of Information and Communications Technology (OICT). New documents are added by the Department for General Assembly and Conference Management (DGACM). Scanned documents and metadata are contributed by the Dag Hammarskjöld Library and the UN Office at Geneva Library.

More information can be found on the website of the United Nations. The following pages are of special interest:

Soft law

Reference works

We have selected these reference works for you based on relevance, author and imprint. Of course there are many more and it is almost impossible to show them all here. More reference works can be found in the following overviews classified by language: English, French, Spanish, German.

Selected books and articles

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

Periodicals, serial publications


  • Oxford Bibliographies in International Law is designed to provide authoritative guidance. The field is rife with debate and controversy, as with most anything that deals with such a complex system of rules and principles meant to govern the relations between states and other institutional subjects, such as the United Nations or the European Union. Because scholarship in this field is so bound up with diplomacy, the vast array of potentially relevant material that appears on the free web can overwhelm even the savviest scholars. With advances in online searching and database technologies, researchers can easily access library catalogs, bibliographic indexes, records of court decisions, and other lists that show thousands of resources that might also be useful to them. In this situation what is most needed is expert guidance. Researchers at all levels need tools that help them filter through the proliferation of information sources to material that is reliable and directly relevant to their inquiries. Oxford Bibliographies in International Law will offer a trustworthy pathway through the thicket of information overload.
  • Public International Law: a Current Bibliography of Articles, (1975-2016) This bibliography has, since 1975, made available to scholars and practitioners information on articles published on all aspects of public international law which are contained in journals, yearbooks, and commemorative compilations, e.g. festschriften. Starting with Vol. 16 (1990), Public International Law, subtitled A Current Bibliography of Books and Articles, has also listed published monographs and collections of essays in addition to commemorative compilations. This bibliography in print has been discontinued as of 2016.

Nowadays, comprehensive bibliographies of public international law are no longer published, simply because library catalogs are more exhaustive. The bibliographies below are some of the latest attempts in print available at the Peace Palace Library.