The referendum vote in 2016 to leave the European Union (Brexit) and the process for its implementation have had a significant impact on the devolution framework, and in particular on its legal mechanisms for ensuring harmonious relations between Westminster and the devolved legislatures, and for resolving conflicts between them. Focusing on the Miller and Scottish Continuity Bill cases, this chapter highlights the problems arising from the use of the mechanisms established in the devolution settlements, primarily designed to ensure that the devolved legislatures do not act ultra vires, for the legal resolution of competence conflicts between both orders of government. Taking into consideration the significant role that the courts play in federal or quasi-federal systems by providing an independent and balanced interpretation of the constitutional framework, this chapter reflects on the effectiveness of these mechanisms in the UK system and argues that, in the light of recent developments, they need to be reformed to enable the access of the devolved institutions to the courts in this context.