The EU is making an ever increasing use of sanctions, often acting autonomously from the UN Security Council, and is a key player in the area. Even if EU institutions declare that autonomous sanctions must be “in full conformity with international law”, the lawfulness of each measure has to be carefully assessed under international law. EU practice is particularly significant as regards the controversial notion of collective countermeasures vis-à-vis erga omnes violations. In any case, EU sanctions are replicated by a significant number of non-member States. Under EU law, the imposition of sanctions is governed by a complex procedure, straddling the TEU and the TFEU. This Chapter discusses the current legal framework concerning the imposition of EU sanctions and their implementation, stressing the crucial role still played by member States in key areas (determination of penalties for sanctions violation, granting of exemptions, enforcement) and explores possible innovations de lege ferenda.