This chapter looks in more detail at the European Union's (EU) sanctions architecture – that is the legal and institutional framework that allows the EU to impose restrictive measures and constrains it in doing so. It analyzes the consecutive waves of sanctions against Iran with a focus on those related to the nuclear file. The chapter examines how the use of sanctions as a policy tool in the case of Iran fits the general rationale for their application. In the early 1980s, the then-nine EU states adopted such measures against the Soviet Union after the imposition of martial law in Poland and against Argentina after its invasion of the Falklands islands. While the United States imposed its set of sanctions against Iran in the wake of the Islamic Revolution of 1979 and the ensuing hostage crisis, the EU and its member states maintained normal, if restrained, relations with Iran.