Introduction to Public International Law Research

Vicenç Feliú is the Associate Dean, Professor of Law, and Director of the Intellectual Property Concentration at Nova Southeastern University Shepard Broad College of Law. He graduated from Franklin Pierce School of Law, Concord, NH, with a JD and an LLM in Intellectual Property and from the University of Washington, Seattle, WA, with an MLIS with an emphasis in Law Librarianship. He is the author of several articles on the Civil Law in Louisiana, Intellectual Property Law, and Legal Research Pedagogy. His articles are published in the Journal of Legal Education, the Louisiana Law Review, the International Journal of Legal Information, Legal Reference Services Quarterly, the Ohio Northern University Law Review, the Villanova Law Review, the John Marshall Review of Intellectual Property Law, the Rutgers Journal of Law and Public Policy, and the Northwestern Journal of Technology and Intellectual Property. Along with Professor Alain Levasseur, he is the co-author of Louis Moreau Lislet: The Man behind the Code of 1808, a book on the life and work of the writer of the Louisiana Civil Code.

1. Introduction

Public international law comprises the laws, rules, and principles of general application that govern the conduct of nation-states and international organizations among themselves, as well as the relationships between nation-states and international organizations with persons, whether natural or juridical. Public international law is sometimes called the “law of nations” or simply “international law.” It should not be confused with private international law, which is primarily concerned with the resolution of conflicts of laws in the international setting, determining the law of which country is applicable to specific situations. In researching this field of law, the researcher must also be aware of comparative law, the study of differences and similarities between the laws of different countries. Comparative law is the study of the different legal systems in the world, i.e., common law, civil law, socialist law, Islamic law, Hindu law, and Chinese law.

As there is no central international body that creates public international law, research in this field requires the use of a wide variety of sources. In the US, a good starting point for research in this area is the Restatement of the Law (Third) and the Foreign Relations Law of the United States, which explain how international law applies in the US. This guide is intended as an introduction to the topic and to help researchers find the most commonly used sources and materials in the area, with a primary focus on electronic research.

2. Major Players

Representatives of nation-states are the primary players in the creation of public international law. These representatives of the nation states include not only the heads of state, such as Presidents, Prime Ministers, and Kings, but also the bureaucratic bodies involved in foreign policy, e.g., state departments, foreign ministries, or the military. Inter-governmental organizations (IGOs), such as the United Nations and the European Union, have also emerged as primary fora for the creation of public international law through the codification of customary law through international treaties.

2.1. United Nations

The UN is the largest and most complex of the IGOs and serves as the umbrella organization for many specialized, subject-oriented organizations. The UN develops, creates, and enforces international law on many levels. The UN homepage is an excellent place to get an idea of how the organization functions. The About the UN page explains the organization’s structure and functions. There is also a page with links to all UN System departments. For researchers, two pages are invaluable: the Documentation Centre and the UN International Law Documentation. The website makes finding UN materials easier by archiving materials dating back to the UN’s inception.

The Union of International Associations (UAI) offers open access to its Open Yearbook, a free service of its subscription-based Yearbook of International Organizations (YBIO), which includes profiles of non-profit organizations working worldwide. Although Open Yearbook offers less information than its proprietary counterpart, it nevertheless serves to promote the activities of international non-governmental organizations (INGOs) and intergovernmental organizations (IGOs). Researchers can find the name, history, mission, structure, and the entity’s last active year in the Open Yearbook.

2.2. Subject-Oriented Organizations

As stated above, the UN serves as an umbrella for many subject-oriented organizations. These specialized agencies of the UN coordinate worldwide activities in specific subject areas. They are organized in different ways, with varying levels of power and structure. They are the result of treaties and sometimes serve to coordinate additional treaties on the same subject. Most of them produce some legislation-like materials and have a form of representative body. Some have adjudicative bodies of limited jurisdiction, but all produce documents such as treaties, records, regulations, and decisions. The UN does not coordinate the publication or distribution of these documents, which can pose a challenge for researchers. However, the UN maintains a Directory of the UN Systems Organizations, which makes finding some of these documents a little easier.

Subject-oriented organization websites include:

• Food and Agriculture Organization
• International Civil Aviation Organization
• International Labour Organization
• International Monetary Fund
• UNESCO
• World Health Organization
• World Intellectual Property Organization

2.2.1. European Union

The European Union consists of 27 member countries, with 9 candidates and 1 potential candidate awaiting admission under the Enlargement policy. EU rules and decisions have a direct effect on the citizens of the member states. Originally, the EU was organized for economic coordination and the development of its member states, but it has since evolved to address social issues as well.

The rule-making and judicial systems of the EU are tied to the ordinary legislative procedure involving the Council of the European Union and the European Parliament. The co-decision procedure, initially introduced by the Maastricht Treaty on European Union (1992) and extended by the Amsterdam Treaty (1997), served as the basis for the ordinary legislative procedure, which took effect with the Lisbon Treaty (December 1, 1999). The European Parliament and the Council jointly adopted most European laws. Everything you ever wanted to know but were afraid to ask about the EU can be found in the University of Luxembourg’s CVCE page, a very useful and informative site.

2.2.2. Council of Europe

The Council of Europe was founded in 1949 to develop common and democratic principles based on the European Convention on Human Rights. It has 46 member states and 5 observer countries: the Holy See, the US, Canada, Japan, and Mexico.

It is organized into three main bodies: the Committee of Ministers, the Council’s decision-making body composed of the Foreign Ministers, or the Permanent Representatives, of the forty-six member states; the Parliamentary Assembly, grouping 648 members (306 delegates and 306 substitutes) from the forty-six national parliaments; and the Congress of Local and Regional Authorities, a consultative body representing local and regional authorities.

3. Sources of Public International Law

The Charter of the United Nations is the founding document of the International Court of Justice (ICJ), the principal judicial organ of the UN. Article 38(1) of the Statute of the International Court of Justice (the Statute), the treaty establishing the ICJ, lists the sources the ICJ may use to resolve disputes. The sources listed in Article 38(1) include treaties, customary law, case law, academic writings, and general principles of law.

4. Introductory Materials

When researching public international law, several resources provide an entry point into the issue. These sources include treatises, encyclopedias, and dictionaries specifically dedicated to the topic. A series of research guides is also available online.

4.1. Treatises

The classic brief work on public international law is James Brierly’s The Law of Nations: An Introduction to the International Law of Peace (Oxford University Press, 1963). It is dated, but it is also a short and well-written introduction to the field. International Law (Oxford University Press, 2007) by A.V. Lowe is the successor to Brierly’s work as a brief introduction to the field. The leading current works in the field are Oppenheim’s International Law, 9th ed., edited by Robert Jennings & Arthur Watts, and Ian Brownlie’s Principles of Public International Law.

Other current standard works covering the spectrum of international law include:

• Aust, Anthony, Modern Treaty Law and Practice, Cambridge University Press, 2018.
• Crawford, James, Brownlie’s Principles of Public International Law, Oxford University Press, 2019.
• Balouziyeh, John, Principles of International Law, Vandeplas Publishing, 2016.
• Armstrong, David, Routledge Handbook of International Law, Routledge, 2011.
• Boyle, Alan, The Making of International Law, Oxford University Press, 2007.
• International Law, edited by Malcolm Evans, Oxford University Press, 2018.

4.2. Encyclopedias

The Max Planck Encyclopedia of Public International Law (Oxford University Press, 2020) (EPIL) is the comprehensive encyclopedia on the subject. The Encyclopedia is continuously updated and extended according to a detailed update strategy. On 1 January 2024, the Max Planck Encyclopedia of International Procedural Law (MPEiPro) was merged into MPEPIL, forming an important subject cluster on international procedural law. The articles in the MPEPIL are written by experts in the areas of law covered and are accompanied by bibliographies on the articles’ topics. These bibliographies can become outdated rather quickly, but they provide an excellent springboard for basic research.

Other useful encyclopedias include:

• Osmanczyk, Edmund, The Encyclopedia of the United Nations and International Agreements, Routledge, 2003
• Forsythe, David, Encyclopedia of Human Rights, Oxford University Press, 2009

4.3. Dictionaries

Many of the specific terms used in international public law will be found in general law dictionaries, such as Black’s. However, the dictionaries listed below focus specifically on international law.

• Parry and Grant Encyclopaedic Dictionary of International Law (Oxford University Press, 2009)
• Fox, James, Dictionary of International and Comparative Law, 3rd edition, (Dobbs Ferry, NY: Oceana Publications, 2004)
• Lindbergh, Ernest, Modern Dictionary of International Legal Terms: English, French, German. (Boston: Little, Brown, 1993)

4.4. Online Research Guides

In addition to the materials on international law found here at GlobaLex, there are other guides specializing in this topic.

• The American Society for International Law – Electronic Resources for International Law
• University of Washington School of Law Library – Treaties and Other International Agreements
• Brooklyn Law School – International and Comparative Law Research
• New York University School of Law – Library Research Guides
• Columbia Law School – Research Guides -Legal Research
• University of Chicago – Legal Research on International Law Issues Using the Internet
• Georgetown Law Library – Foreign and Comparative Law Research Guide
• The Harvard Law School Library – International Legal Research

5. Treaties

The 1648 Peace Treaties of Westphalia, reproduced by the Avalon Project at Yale Law School, established the framework for modern treaties and recognized the sovereign’s right to govern freely from outside interference. By the 20th century, the subject matter of treaties had been expanded to include humanitarian law, criminal law, intellectual property, the sale of goods, the environment, and outer space, among other topics. Today, treaties have become the principal source of public international law and can also create rights for individuals.

Treaties may be bilateral (between two countries) or multilateral (between three or more countries). The treaty text may provide for the manner in which it takes effect. Generally, treaties enter into force when they have been signed and ratified by a certain number of parties. Parties to a treaty may ratify a treaty with reservations or other declarations unless the terms of the treaty place restrictions on those actions. A reservation is a country’s attempt to modify certain terms of the treaty, as it applies between itself and other countries. The Vienna Convention on the Law of Treaties is the UN agreement that governs the law of treaties, and it can serve as a guide to how treaties and other fundamental concepts are made.

5.1. Researching Treaties

Treaty research is a topic that can be the subject of its own detailed guide. However, when conducting treaty research, the researcher needs to ask key questions to determine who is best positioned to address the question. These questions should be:

• Is it a bilateral or multilateral treaty?
• Who are the parties to the treaty?
• Is the treaty in force?
• Has the treaty been signed, ratified, repudiated, or modified?
• Are there reservations to the treaty?
• Is there an international organization that oversees or administers international law in the subject area of the treaty?

5.2. Treaties to Which the US Is a Party

Treaties in force to which the US is a party are compiled in Treaties in Force: A List of Treaties and Other International Agreements of The United States (US Dept. of State, USGPO, 1955- ) and A Guide to the United States Treaties in Force (Buffalo, N.Y., W.S. Hein Co., 1982). These treaties can be found online at the US State Department’s Treaty Affairs website, which includes not only treaties in force but also those under consideration. They can also be found in commercial databases such as HeinOnline, LexisNexis (US Treaties on Lexis), and Westlaw (US Treaties and Other International Agreements). A Guide to the United States Treaties in Force is also published commercially in an electronic format by HeinOnline.

If the treaty is out of force, it can be found in the United States Treaty Index (Buffalo, N.Y., W.S. Hein, 1991- ). This work is also published electronically in commercial databases such as HeinOnline, Lexis, or Westlaw.

5.3. Treaties to Which the US Is Not a Party

Researching treaties to which the United States is not a party can pose a greater challenge for the researcher.

Multilateral treaties are published in sets, such as the United Nations Treaty Series (UNTS), and in some cases on the web. However, only treaties deposited with the UN Secretary General become part of the UNTS. Although most multilateral (and many bilateral) treaties are deposited with the UN as a matter of course, states are under no specific obligation to do so. A good source of information on the role of the UN as a treaty depository is the Summary of Practice of the Secretary-General as Depository of Multilateral Treaties on the UN website. The Treaty Handbook (United Nations, 2012), written by the Treaty Section of the UN Office of Legal Affairs, is another excellent source of information on this topic. The UNTS is available at the United Nations Treaty Collection website. This searchable database includes over 40,000 bilateral and multilateral treaties in scanned format. The Fletcher School Multilateral Project had the text of over 200 international multilateral treaties and other instruments; unfortunately, this project has been discontinued and is no longer updated. However, the archived pages of the project are still viewable using Archive-It. Most of the texts still available through the archived pages date from 1945 or later, but the collection also includes historical texts, from the 1648 Treaty of Westphalia to the Covenant of the League of Nations.

Bilateral, obscure, or historic treaties can be more difficult to find. These treaties are generally published only in the treaty series or gazettes of the signatories, or in commercially produced, topical compilations. In these cases, the researcher needs as much information as possible about the treaty before beginning research.

5.4. Guides to Treaty Research

• New York University School of Law Library – International Law – General Resources and International Law – Specialized Resources
• University of Washington School of Law Library –
• Treaties and Other International AgreementsThe Harvard Law School Library – Finding a Treaty Without a Citation
• Columbia Law School – Research Guides -Legal Research
• University of Chicago –
• Fundamentals of Treaty Research: U.S. and Non-U.S. (Electronic Resources)Duke Law Library – Treaties

6. Customary Law

In international law, customary law refers to the Law of Nations. The Law of Nations comprises the legal norms that have developed through interactions between states over time. The concept implies that states are expected to carry out their affairs consistently with past-accepted conduct. Customary law can change based on states’ acceptance or rejection of particular acts. Norms that achieve universal acceptance can become peremptory norms, binding and unchangeable except by a norm of comparable strength. Many international treaties are attempts to codify existing customary law.

To find customary law, start by searching for relevant texts and treatises, law review articles, and judicial decisions from national and international tribunals. Statements made in landmark UN resolutions and declarations can also be helpful. International legal matters are frequently litigated in American courts, so check federal and regional digests for cases. Legal encyclopedias, such as Corpus Juris Secundum (CJS) and American Jurisprudence, 2d (Am Jur 2d), may also contain relevant materials.

6.1. Guides to Customary Law Research

• GlobaLex – Researching Customary International Law, State Practice, and the Pronouncements of States Regarding International Law
• Duke – Customary International Law (as part of International Legal Research Tutorial)
• Georgetown University – Selected Treatises on Customary International Law (as part of International Law Research Resources)

7. Case Law

7.1. International Court of Justice

As stated above, the UN Charter designates the ICJ as the principal international court of law. Its main mission is to settle disputes between nations, and its holdings are the strongest statement of what international law is in a particular situation. The ICJ has a dual jurisdiction: it decides, in accordance with international law, disputes of a legal nature that are submitted to it by States (jurisdiction in contentious cases), and it gives advisory opinions on legal questions at the request of the organs of the United Nations or specialized agencies authorized to make such a request (advisory jurisdiction).

The ICJ maintains an archive on its website of all contentious cases and advisory proceedings going back to 1947. This page also lists all pending cases before the court. Recent developments include the landmark advisory opinion delivered on July 23, 2025, on “the obligations of states with respect to climate change,” which clarified states’ obligations regarding climate protection and human rights.

The Registry is the official publication of the court and consists of a series of materials covering the full range of documents created by the court. The decisions of the Court, in both English and French, are published in the I.C.J. Reports. Each decision is published as soon as possible after it is given in an unbound fascicle, and an analytical index of the previous year’s decisions is published early each year. The official citation of the series is I.C.J. Reports, with an indication of the year, e.g., Fisheries Jurisdiction (Spain v. Canada), Jurisdiction of the Court, Judgment, I.C.J. Reports 1998, p. 432.

Pleadings and oral arguments are published after the termination of each case and contain the documentation relating to the case in the original language, e.g., English or French. This set comprises the document instituting proceedings, the written pleadings and (selected) annexes, the verbatim record of the oral proceedings, any documents submitted to the Court after the closure of the written proceedings, and selected correspondence. The official citation is I.C.J. Pleadings, with the short title of the case, e.g., I.C.J. Pleadings, Elettronica Sicula S.p.A. (ELSI), Vol. I.

In addition, the Registry also publishes the I.C.J. Yearbook, the I.C.J. Bibliography, and Acts and Documents. Acts and Documents is a series containing the basic texts about the court. The Yearbook provides an account of the Court’s work from August 1 of the preceding year to July 31 of the current year. There is also a French edition of this publication, the Annuaire. The Bibliography is a listing of such works and documents relating to the Court as have come to its attention during the previous year.

7.2. European Courts

There are two distinct and separate court systems within the European framework. The first court system, the Court of Justice of the European Union (CJEU), based in Luxembourg, is associated with the EU and handles commercial and social issues within the EU—the second court system. The European Court of Human Rights, based in Strasbourg, is part of the Council of Europe and principally deals with human rights issues. These two systems have no relationship with each other.

7.2.1. The Court System of the European Union

The CJEU comprises three bodies: the Court of Justice, the General Court, and the Civil Service Tribunal. The Commission, the General Court, or the CJEU may make decisions within the European Union system. However, older cases may have had an opinion of the Advocate-General as well, but the CJEU has stopped printing those decisions in the official reporter. Since 2005, cases involving the EU civil service have been heard by the Civil Service Tribunal. These cases were originally heard by the CJEU and, following its creation in 1988, by the General Court. The Civil Service Tribunal may not hear and determine cases between national administrations and their employees.

The CJEU’s website offers detailed descriptions of the Court’s institutions and is a great place to get a general understanding of how it works. It also includes a section on case law since the Court’s inception. CJEU case law is also available through Eur-Lex, the portal for EU legal materials. The official reporter for the CJEU was the Court of Justice of the European Communities, Reports of Cases Before the Court. However, as of April 2014, this print reporter ceased publication—see the CJEU’s statement (as archived by the Wayback Machine) and page on presentation of the European Court Reports. The last volumes issued were 2011 v. 12C for Series I and 2011 v. 11/12 for Series II. Recent judicial statistics (2024) show that the ECJ received 920 new cases, a 12% increase over the previous year, and that a record 1,206 cases were pending before the ECJ as of December 31, 2024.

7.2.2. The European Court of Human Rights

The ECHR is the result of the European Convention on Human Rights and is administered through the Council of Europe. The Court, as presently constituted, was brought into being by Protocol No. 11 on November 1, 1998. This amendment made the Convention process wholly judicial, as the Commission’s screening function was entrusted to the Court itself, whose jurisdiction became mandatory.

Access to the European Court of Human Rights case-law database is through the Court’s Knowledge Sharing Platform (ECHR-KS), which connects to a HUDOC Portal. This is a powerful and user-friendly system, which provides free online access to the judgments, decisions, resolutions, and reports of the European Court of Human Rights, the European Commission of Human Rights, and the Committee of Ministers. The database is updated regularly, making it an efficient research tool.

The official reporters for the court are the Publications de la Cour Européenne des Droits de l’Homme. Série A, Arrêts et Décisions = Publications of the European Court of Human Rights. Series A, Judgments and Decisions. (Strasbourg: Greffe de la Cour, Conseil de l’Europe, 1961-1996) and Recueil des Arrêts et Décisions (Köln: Carl Heymanns Verlag, 1996- ).

7.3. Other International Courts

7.3.1. Inter-American Court of Human Rights

Created in 1979 under the umbrella of the Organization of American States (OAS), the Inter-American Court of Human Rights is the OAS’s autonomous judicial institution. The Court’s objective is the application and interpretation of the American Convention on Human Rights and other treaties concerning this issue. The Court’s website links to cases at the merits stage, provisional measures decisions, advisory opinions, and monitoring compliance with judgments. It also maintains an instruments page with a comprehensive collection of treaties, conventions, and protocols materials relating to human rights for the Universal, Inter-American, European, and African systems. The University of Minnesota maintained a mirror site to the Court’s website with a list of basic documents relevant to the Court. This site was archived in 2023 and is no longer updated, but can serve as a historical resource.

Official reports for the Court are

• Inter-American Court of Human Rights Serie A, Fallos y Opiniones / Series A, Judgments and Opinions (San José, Costa Rica: Secretaría de la Corte, 1982- ).
• Serie B, Memorias, Argumentos Orales y Documentos / Series B, Pleadings, Oral Arguments and Documents.
• Serie C–Resoluciones y Sentencias/ Series C–Decisions and Judgments

7.3.2. International Criminal Court

The International Criminal Court (ICC) is an independent, permanent court established by the Rome Statute of the International Criminal Court. The ICC tries persons accused of the most serious crimes of international concern, namely genocide, crimes against humanity, and war crimes. It is a court of last resort and will not act if a case is investigated or prosecuted by a national judicial system unless the national proceedings are not found to be genuine. As of June 2025, 125 countries are parties to the Rome Statute, but the US is not one of them, and several states have announced intentions to withdraw.

The Court’s Official Journal is published electronically, and the website contains a wealth of materials and information on the Court.

7.3.2.1. Special Situation Courts

Since the creation of special courts to address war crimes after World War II, a series of other courts have been established to handle specific international concerns. The following is a list of the most prominent of those courts.

• Nuremberg Trials: The Avalon Project at Yale Law School
• Legacy Site for the International Criminal Tribunal for Rwanda
• Legacy site for the International Criminal Tribunal for the Former Yugoslavia

Iran-US Claims Tribunal

8. Journals

The list of journals on international law is exhaustive, and the researcher would be well served to begin with an index, such as the Current Index to Legal Periodicals or the Index to Foreign Legal Periodicals, to find articles on the topic. The following is a small list of journals specializing in international law to help the researcher get started. They are available commercially through LexisNexis, Westlaw, or HeinOnline, although some websites link to the full text of articles.

• Fordham International Law Journal (full text from vol. 32)
• The European Journal of International Law (full text)
• Harvard International Law JournalCornell International Law Journal (full text)
• American University International Law Review (full text)
• NYU Journal of International Law and Politics (full text from vol. 36)
• Columbia Journal of Transnational Law (full text from vol. 57)
• Leiden Journal of International Law

9. Useful Links

UC Berkeley School of Law and Duke University School of Law: International Legal Research Tutorial. A collaborative project designed to teach research strategies for print and electronic resources on international legal materials.

See also: European Eastern Neighborhood Policy and Enlargement Negotiations, Check Current Status, and European Commission.