On Monday 21 May 2018, the US Secretary of State announced that, as a result of its withdrawal from the Joint Comprehensive Plan of Action (‘JCPOA’ or ‘Iran Nuclear Deal’), the United States is set to impose the ‘strongest sanctions in history’ against Iran. While the remaining states parties are committed to preserve the Iran Nuclear Deal, whether the JCPOA can in fact survive in the face of the US change of heart is a matter of uncertainty. Of particular concern is the effect that the resumption of US economic sanctions will have on non-US companies that have flocked to Iran in the aftermath of the JCPOA. Unlike the sanction programmes implemented against Iran by various states before 2015, the US measures present distinctively extraterritorial features, directly targeting foreign companies carrying out business with Iran despite the absence of a significant connection with the United States. The European Union has already vowed to take action in order to protect its trade interests and to ‘block’ unwarranted interference by the United States. As tension in the transatlantic relations mounts, serious questions arise concerning the legality of the US sanctions regime under international law. This post will focus in particular on the compatibility of these measures with the international rules governing the assertion of jurisdiction by states. Läs artikel