Preface; List of contributors; Introduction: the constitutional tensions of Brexit Oran Doyle, Aileen McHarg and Jo Murkens; Part I. Territorial Pressures in Ireland and the United Kingdom: 1. Subsidiarity, competence, and the UK territorial constitution Jo Hunt; 2. Brexit and the mechanisms for the resolution of conflicts in the context of devolution: do we need a new model? Elisenda Casanas Adam; 3. Beyond matryoshka governance in the 21st century: the curious case of Northern Ireland Sylvia de Mars and Aoife O'Donoghue; 4. Political parties in Northern Ireland and the post-Brexit constitutional debate David Mitchell; 5. The constitutional significance of the people of Northern Ireland C. R. G. Murray; 6. The constitutional politics of a United Ireland Oran Doyle, David Kenny and Christopher McCrudden; 7. The minority rights implications of Irish unification James Rooney; Part II. Institutional Pressures and Contested Legitimacy: 8. Populism and popular sovereignty in the UK and Irish constitutional orders Eoin Daly; 9. Party, democracy and representation: the political consequences of Brexit Malcolm Petrie; 10. Westminster versus Whitehall: what the Brexit debate revealed about an unresolved conflict at the heart of the British constitution David Howarth; 11. Brexit and the problem with delegated legislation Adam Tucker; 12. Litigating Brexit Christopher McCorkindale and Aileen McHarg; 13. The law officers: the relationship between executive lawyers and executive power in Ireland and the United Kingdom Conor Casey; 14. In search of the constitution Martin Loughlin.