This paper argues that Brexit will alter not one but two unions: the European Union and the United Kingdom. It begins with an overview of the U.K.’s constitutional arrangements, outlining how power has been devolved to the country’s nations and regions. It then discusses how Brexit has challenged these structures, with a focus on Northern Ireland and Scotland. Next, it considers how political dynamics in London, Dublin, Edinburgh, and Belfast are complicating efforts to resolve these tensions. Finally, it details how Brexit will affect Northern Ireland and Scotland in political and socio-economic terms, and force U.K.-wide debates about unresolved identity issues and the nature of devolved governance.

A publication within the framework of the initiative Brookings - Robert Bosch Foundation Transatlantic Initiative (BBTI).