TRICI-Law project (the acronym stands for “The Rules of Interpretation of Customary International Law”) is a 5-year European Research Council Starting Grant project. The project aims to prove that customary international law is open to interpretation, just as treaty rules are. Moreover, it aims to demonstrate that the process of interpretation of customary international law, which is an unwritten source of law, follows certain rules that can be induced from the case law of international courts and tribunals.