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International Legal Research: Introduction

This Guide covers essential print and electronic resources for researching international and foreign law.


Public international law, as traditionally defined, is the law governing relations between nation states.

Foreign law is simply the national law (also known as domestic or municipal law) of another country.

Private international law is a confusing term in that it refers to the national law(s) governing the cross-border interactions of private (non-state) parties, rather than international law. The question that often arises in such instances is "which country's law applies?". Private international law is, therefore, sometimes referred to as conflicts of laws, although the parties can select the law which governs their transaction by contract. A number of private international law topics are covered by treaty (i.e. family law, estates and trusts, litigation). Since treaties are characteristic of the public international law system, the idea that a treaty would apply to a private international law issue can be confusing as well. Often the aim of such treaties is to harmonize national laws. 

The sources of public international law are enumerated under Article 38 of the Statute of the International Court of Justice, which is appended to the Charter of the United Nations. Those sources are, as follows: treaties, custom, general principles and case law and scholarly commentary as a subsidiary means for determining the rules of law. Treaties, custom and general principles are primary sources of law in the public international legal system. Court decisions and scholarly writings are secondary sources. Treaties are written agreements between nations. Customary law is state practice which is done out of a sense of obligation. General principles are those general legal principles which courts all over the world have recognized. Note that the documentation of inter-governmental organizations (IGOs) like the United Nations or so called "soft law" is not listed as a source of law under the ICJ Statute, perhaps because the Statute was drafted before the proliferation of IGOs.

Treaties are written instruments which can be found in several sources, both official and unofficial. In contrast, custom and general principles are not written down. Evidence of custom and general principles must be derived from other sources, such as treaties, UN documentation and court decisions.

The purpose of this guide is to introduce researchers to basic treaty and other sources for researching public and private international law. In addition, this guide will cover foreign law research and specific topics in international law, including international human rights law, intellectual property, international trade and international environmental law.



International legal materials are generally found under Library of Congress (LC) call number KZ.

Sample Library of Congress subject headings include:

Comparative legal materials (i.e. titles which compare or contain laws of multiple countries) can be found under call number K or subject headings, like those below, with no specific jurisdiction designation:

Catalogs are the key to using any library collection. Use the catalog when you want to find book titles on a particular topic. In addition to checking the JMLS library catalog, you can expand your search for relevant books titles to other libraries throughout the world by using Worldcat. Note that the same LC call numbers and subject headings used in this library's catalog are used in other law libraries and Worldcat.


    Worldcat, as its name suggests, is a catalog of book titles held by libraries all over the world. Worldcat uses the same Library of Congress subject headings as those used in the JMLS Law Library catalog. Thus, you can use Worldcat to expand your research beyond the four walls of this Library. Use the advanced search template to search as shown below.

     A traditional catalog is a tool designed to enable researchers to find book titles in a library collection. To find articles, researchers have to use a separate but similar tool known as an index. However, some catalogs now blur this distinction by including records for book titles and journal articles. 

    The Peace Palace Library catalog is an example of this new hybrid. It makes international legal research very efficient as researchers can now find book titles, chapters and articles on international law issues all in one place. 



    For more information on the use of catalogs and indexes, see the Treatises and Law Review Articles tab.  



    Reference Titles: Dictionaries

    Boczek, International Law: a dictionary. 6th floor Reference KZ1161 .B63 2005

    Fellmeth, Guide to Latin in International Law. 6th floor Reference K52 .L37 F45 2009


    Parry & Grant Encyclopaedic Dictionary of International Law. 3rd ed. 6th floor Reference  KZ1161 .P37 2009



    Oxford English Dictionary


    Ozmanczyk, The Encyclopedia of the United Nations and International Agreements, 7th floor KZ4968 .O86 2003

    Max Planck Encyclopedia of Public International Law   KZ1160 .E52 1981

    Abbreviations & Citation

    Cardiff Index to Legal Abbreviations



    Bluebook: a uniform system of citation (20th ed. 2015) KF245 .Un3 2015 Reserve & Academic Success

    Request a Research Appointment

    Need more help? Reference librarians are available to meet with students in one-on-one sessions (or in small groups) to discuss research strategies, recommend relevant resources or review specific topics of legal research. 

    Contact with the subject you're researching and when you would like to meet. A librarian will get back to you to set up an appointment. You can also schedule an appointment on the library homepage by clicking "Schedule an Online Research Appointment." We ask that you request your appointment at least 2 days in advance, but remember that you can always stop by the reference desk for immediate help with a quick research question.