It is a real challenge to deal with the subject of economic sanctions, a topic where law meets politics, while touching upon almost all areas of the law: public international law, private international law, even private law and public law, not to mention the "internal" law of certain international organizations particularly active in the field, especially the EC/EU. Sometimes considered as a "punitive" and "brutal" instrument, economic sanctions - even when adopted by a universal institution - have often proven to be ineffective. While the issue of the effectiveness of sanctions, as such, goes indeed beyond legal considerations, it would be fallacious to think that lawyers should confine themselves to an abstract analysis of the phenomenon or that legal tools would have practically no effect on the shape of the measures to be taken. On the contrary, law is at the core of the very concept of sanctions, and it is through legal tools that sanctions may be tailored to the ends to be pursued, reinforcing, by so doing, the effectiveness of the international legal system. In light of the current developments under way - which concern both institutional sanctions and decentralized countermeasures, as well as the often inextricable intertwining between these two levels - the judicious choice made by the Curatorium of the Academy was propitious for taking a fresh look at the issue of unity and diversity of sanctions under international law.