Skip to main content
It looks like you're using Internet Explorer 11 or older. This website works best with modern browsers such as the latest versions of Chrome, Firefox, Safari, and Edge. If you continue with this browser, you may see unexpected results.


Information to help you carry out legal research

International legal system

International law is a system of rules and principles governing the relationships between states and the working of international organisations.  Major sources of international law are:

  • treaties (bilateral and multilateral)
  • customary rules and practices
  • judicial decisions
  • resolutions of international organisations

Judicial decisions

Judicial decisions play a role in clarifying the sources of international law  They include decisions from the

Decisions are also available on Westlaw and Lexis.   On Lexis use the International  sources.  On Westlaw, access the international material via Services and then select Multinational materials - Court and Tribunal Cases to see a range of sources.

Resolutions of international organisations

These decisions can play a major role in determining customary law and identifying when practices are belived to be obligatory (opinio juris).  They include resolutions of the Security Council and the General Assembly of the United Nations.


Treaties create binding legal obligations between subjects of international law.

You can access treaties on the UN Treaty Database.

The Flare Index to Treaties is a searchable database of basic information on over 2,000 of the most significant multilateral treaties and some bilateral treaties concluded between 1353 and the present, with details of where the full text of each treaty may be obtained in paper and, if available, electronic form on the Internet.

You can find official documents recording the negotiations, drafting, and discussions during the process of creating a treaty at Yale University's Collected Travaux Préparatoires.