Definitions of Customary International Law
Considered, along with treaties and "general principles of law," to be a significant source of international law, custom reflects "a general and consistent practice of states followed by them from a sense of legal obligation." A related concept is "jus cogens' or "peremptory norms," international legal principles so fundamental that no derogation from those norms is deemed permissable. In determining which norms constitute custom, scholars and practitioners must look to many sources to establish both the "state practice" and "opinio juris" requirements. As such, researching customary international law is often a difficult task. This guide does not aim to provide particular strategies for researching customary international law. Rather, it represents a more modest effort to suggest resources available at Vanderbilt or on the web for those who need to better understand custom in international law, or begin generally identifying available materials.
