The following are some of the journals dedicated to publishing articles on Mexico or Latin America. It may be useful to browse the table of contents (you should be able to do this electronically for most or all) to see if you can find any special issues focusing on your theme or particularly useful articles.
EcoAméricas: A Monthly Report on Development and the Environment in Latin America
Estudios Mexicanos/Mexican Studies
Hispanic American Historical Review (HAHR)
Journal of Latin American Studies (JLAS)
Latin American Research Review (LARR)
Full text of law reviews/legal periodicals plus primary sources such as the Code of Federal Regulations; Federal Register; Foreign Relations of the United States (FRUS); Treaties and Agreements Library; United States Code; U.S. Attorney General Opinions; U.S. Congressional Documents; U.S. Federal Agency Documents, Decisions, and Appeals; U.S. Federal Legislative History Library; U.S. Statutes at Large; World Constitutions Illustrated. Includes additional databases: National Survey of State Laws; Religion and the Law; Subject Compilations of State Laws; Women and the Law (Peggy); World Treaty Library