This chapter explores the European Union’s relationship and contribution to the international law of global security through the lens of ‘ambivalence’. The reasons for this approach are threefold. First, that relationship oscillates between symbiosis and friction. On the one hand, the European Union (EU) has been gradually integrated into the global security architecture. On the other hand, the EU, as a power bloc and ‘autonomous’ legal community, also provides a source of conflict with, disassociation from, or destabilization of, global security arrangements. Second, the interaction between EU law and global security law, as well as the substantive contribution of the EU to the law of global security, produces mixed results. Finally, the ambivalence of the EU as a ‘global security provider’ has also explanatory value when it comes to contemporary developments and challenges, particularly as they emerge from the EU’s response to the increased ‘questioning’ of the European project and the global liberal order more generally, and that cut across several aspects of global security.