If you simply need to locate the text of a treaty (aka convention, agreement, covenant, protocol, etc.), searching the treaty's title in your preferred search engine will generally lead to a copy of the treaty text from a government or intergovernmental organization (e.g., United Nations) website. Alternatively, search for the treaty in the Flare Index to Treaties.
If you need to ensure you locate a citable version of the treaty, use treaty citation information (U.N.T.S., U.S.T., etc..) to determine which database(s) will contain a copy of the treaty. Refer to Bluebook Rule 21.4 and Table T4 on treaty citation to learn more about citation formats and preferred sources. Many of the most common sources are below, but check the Additional Guides section for ideas on finding other treaty sources if you don't find your source below.
In addition to finding the text of a treaty using the Source Collection resources, treaty research involves locating status information about the treaty. This includes:
This information can often be found on the site where you located the treaty text. If it's not there, a web search of the treaty title will generally lead to a government or intergovernmental organization (e.g., United Nations) website with this information.
Major treaties may be the subject of multiple books, including one or more commentaries. Commentaries generally provide article by article authoritative treaty analysis and are a tremendous source of information about a treaty. Commentaries can usually be identified by the use of the word "commentary" in the book title.
Search for commentaries and other books about a treaty using a subject search for the treaty in a library catalog.
Travaux préparatoires generally include the negotiating, drafting, and preparatory history for a treaty and can be consulted to clarify treaty provisions. For major treaties, there's often a compiled source providing the travaux or a guide to it in one location, for others there may be a compilation of the documents from the conference that led to the treaty. This information may also be available through a website about the treaty or created by a relevant organization.