After locating applicable treaties and organizations using encyclopedias, you can use handbooks and scholarly commentaries to deepen your understanding of the legal texts.
Commentaries: these provide article-by-article analysis of a legal text. In the library catalog, search [name of the agreement] commentary
Handbooks are collections of research essays covering a specific topic. Below are some examples. Find more with a catalog search for human rights handbook
The Oxford Handbook of International Human Rights Law (Dinah Shelton ed., 2013).