When dealing with treaties to which the United States is not a party, it’s generally more difficult to find bilateral treaties than it is to find multilateral treaties. States are not obligated to deposit bilateral treaties with the United Nations, and these treaties are less likely to be collected in large sets.
For non-U.S. bilateral treaties, your best bets are to look in: (1) general databases and collections publishing both bilateral and multilateral treaties; (2) official gazettes and country treaty series of the relevant parties; and (3) subject-specific treaty databases.
The two best general databases to start your bilateral treaty search are the previously-mentioned United Nations Treaty Collection (where you can filter by “Treaty type” and select “Bilateral”) and HeinOnline’s World Treaty Library (where you can search HeinOnline’s extensive collection).
Many countries publish their bilateral treaties in official gazettes or collect their treaties on government websites and repositories.
To find official gazettes for specific countries, we recommend going to the Foreign Law Guide, browsing to the relevant country, and clicking on the “Official Gazette” link under Primary Sources. Other good directories for official gazettes include the Library of Congress’s Guide to Law Online and GlobaLex’s Foreign Law Research guides.
To find national treaty series and collections online, we recommend checking WorldLII’s International Treaties Collection and the United Nations Audiovisual Library of International Law’s List of Treaty Collections.
Finally, the World Treaty Index [1900 – 1980] contains bilateral treaties and a list of “Source Codes” in its Thesaurus. Because the World Treaty Index was last updated for treaties completed by 1980, these sources may no longer exist and must be updated.