I hope it has become clear that in researching international law you may need to work with materials from legal systems other than the United States. Finding applicable cases, statutes, regulations, or treaties may involve working with the domestic law research systems of any number of countries. Besides finding the raw information, such as treaties, it can be important to understand how international law fits into the legal system of a country. It can be dangerous to assume that a treaty is followed in another nation in exactly the same way as the United States, especially if that country’s legal background is substantially different from ours. In practice, lawyers rely on foreign firms to provide them assessments of the issues in this area.
In a gross over-simplification, the three major legal systems of the world are the Common Law System, developed from English sources and dominant in the areas colonized by England, Islamic law, dominant in the Middle East, and the Civil Law System, developed from Roman law and dominant everywhere else. A fourth system, Socialist law, developed in countries with Marxist governments, but it is now generally perceived as an off-shoot of Civil Law, and the ex-socialist countries tend to be re-developing along civil law lines. There are a number of less widely spread systems throughout the world which struggle to survive against the imperialism of the ex-colonial systems.
Some areas, such as Louisiana, Scotland, and South Africa are perceived as "mixed jurisdictions" due to their blending of Civil and Common law influences.
A good introduction to Civilian thinking is John Merryman’s The civil law tradition : an introduction to the legal systems of Western Europe and Latin America, (Comp 078 M554 1985, Cellar). On comparative law generally a more recent work is Peter de Cruz’s Comparative law in a changing world, (Comp 300 D359c 1999, Cellar). A good starting point might be an older, non-academic work, The Faces of Justice, by Sybille Bedford (Comp 870 B39, Cellar).
The leading tool for starting comparative law research is Foreign law : current sources of codes and basic legislation in jurisdictions of the world, by Tom Reynolds and Arturo A. Flores. It is kept at reference at K38 .R49 1989. This is a multivolume looseleaf annotated bibliography with a section on each country in the world.
For a good background presentation for each country and territory in the world, the best paper source is The Statesman's year-book, (JA51 .S7, 3rd Fl REFERENCE), which has been published since 1864. However, a faster start might be made through the web version of the CIA guide known as "The World Factbook, 1999."
Within general comparative law there is recognition that there is a subject which might be called "comparative international law" The basic works are treatises which expound upon a particular country's application of international law. Examples include:


Or they can come in a larger form:
Other Useful Websites

The leading informal comparative law website is "Foreign Primary Law on the Web", compiled by Timothy F. Mulligan at the University of Houston. It has references to material from just over 90 countries. However, some of the material from some countries is pretty skimpy.
Mirela Roznovschi’s site of "Foreign Databases By Jurisdiction" covers fewer countries (43) than Mulligan’s, but has useful introductory paragraphs for each country.
An interesting international database of constitutional texts can be found at http://www.servat.unibe****/icl/info.html.