Brexit was a great revealer in many respects. In relation to Northern Ireland, it revealed the almost invisible role that joint EU membership had played in providing a scaffold for the peace process in the province and in resolving a postcolonial conflict with cross-border dimensions. In addition to EU political support and in facilitating good relations between Ireland and the UK, joint membership of the single market and customs union, along with the Common Travel Area between the two jurisdictions, reduced the practical and symbolic effect of the border between Ireland and Northern Ireland. It was thus the functional effects of single market law which provided the context within which a postcolonial conflict with cross-border dimensions could be managed. Brexit, particularly of the ‘hard’ variety, threatened to reintroduce this border, undermining a key element of the peace process. The Ireland/Northern Ireland Protocol or Windsor Framework is an imperfect substitute which results in an extremely complex legal landscape of multiple interacting sources of law: a form of legal pluralism or even legal entanglement.