This chapter considers Article 50 TEU with constitutional provisions that allow for secession. The Article 50 TEU process bears some similarity to secessionist constitutional processes around the globe, while the European Union (EU) Act 2018 aims at effectively dealing with similar problems that the continuance clauses try to solve. At the same time, the UK’s withdrawal from the EU could have a domino effect on its territorial constitution. The chapter explains the constitutional framework concerning the possible independence of Scotland and reunification of Ireland. The famous “backstop option” provided by the Protocol of Ireland/Northern Ireland of the draft UK Withdrawal Agreement, however, has been portrayed as a threat to the UK constitutional and territorial integrity. The decision of the UK government to leave the single market and the customs union raises unique and complex legal and practical issues with regard to the Irish border, many of which are linked to the Good Friday/Belfast Agreement.