The system of sanctions is a key element of law enforcement, so it is of particular importance to have a clear and doctrinally based system of sanctions. However, new areas and issues are emerging in the field of administrative sanctions which call into question principles previously thought to be clear and push them in new directions. One such issue is the question of complementary sanctions, which has raised the question of the permissibility of parallel sanctions and is closely linked to the principle of ne bis in idem. The paper outlines the framework in which the main issues of administrative sanctioning arise and shows how they interact. It looks at how fundamental international decisions may affect the frontier issues of administrative sanctions, how Strasbourg and EU practice has evolved, and how this has affected domestic law.