This semestrial Master course, taught in English, focuses on the international responsibility regime of States and international organisations. After a general presentation of the ARSIWA and ARIO, various specific issues (e.g. the international responsibility regime of the EU and its Member States, the responsibility regime of the ECHR and the responsibility regime of the UN) and procedural issues (e.g. diplomatic responsibility action) are addressed. The course is supplemented by seminars in which students are asked to present and discuss various topics based on the readings provided.