In their recent drives for full self-determination, separatist actors in Catalonia and Scotland have taken for granted their regions’ continued membership of the European Union after independence. Is such an assumption warranted? This chapter tries to provide an answer by looking at the arguments put forward by the actors involved and at the relevant literature, especially the legal arguments on the status of a territory seceding from an EU member state. It highlights the highly political nature of this situation and presents alternative scenarios concerning the two cases. It concludes that, although final outcomes will depend on the characteristics of each self-determination process, it is likely that an interim solution preserving at least some core substantive elements of the rights and duties attached to EU membership over the territory of these two regions is likely to be agreed upon pending the results of negotiations on a permanent settlement.