These sources provide some basic information about various organizations and their rights and responsibilities under international law. To locate the constitutions or constituting documents for IOs, see their websites or collections of treaties, like UNTS.
Keywords: international organizations (or organisations), inter-governmental organizations, IGOs, international agencies, international institutions, non-state actors, non-governmental organizations, NGOs.
Databases (UCB only):
Max Planck Encyclopedia of Public International Law
Select "Advanced Search" and then search by "title": “international organizations” or “universal international organizations and institutions." You can also search by keywords or the name of the organization in the heading field. Also available in print.
Oxford Bibliographies: International Law
For example, see the articles on "international organizations" or "institutional law".
Parry and Grant Encyclopaedic Dictionary of International Law
Search by the name of the organization or keyword. Short and concise information.
International Encyclopaedia of Laws: Intergovernmental Organizations
Covers many international organizations -- UN, ILO, etc.
Oxford International Organizations (OXIO)
Contains a collection of annotated documents pertaining to the law of international organizations.
Advanced Introduction to the Law of International Organizations (2015).
Reviews the basics about international organization law, members, organs, etc.
An Introduction to International Organizations Law (3d ed., 2015).
International Organizations and the Law (2018).
Addresses the laws relating to international organizations.
Research Handbook on the European Union and International Organizations (2019).
The focus is on the EU and its relationship with other IOs.
The Ashgate Research Companion to Non-State Actors (2011).
Goes a bit beyond IOs and includes NGOs.
Research guides are good places to start your research. These guides identify relevant sources and websites as well as explain how to research a specific topic or organization. To locate more guides, search Google using the name of the organization and "research guide."
UC Berkeley Law Library Research Guides
Guides on topics and organizations.
Some guides on organizations, lots of guides by topic or country -- the quality varies. To locate IO guides, select "International Law Research."
International Labour Organization, Research Guides
Guides by topic: child labour, forced labour, indigenous peoples, and more.
United Nations Documentation: Research Guide
Includes information on how to read document symbols.
WTO Research Guide
A terrific guide on the WTO, both print and electronic sources.
List of IGOs: Getting Started
A general, non-law, guide.