The results of the Brexit referendum are proving to be as much a threat to the United Kingdom's unity as they are to the unity of the European Union. For Scotland and Northern Ireland, two countries in the United Kingdom where a majority of voters opted to remain in the European Union, the decision to leave the Continental bloc is especially concerning. Scotland's 2014 independence referendum and more recent opinion polls in Northern Ireland highlight their dilemma: Voters in each place want to remain in the United Kingdom and in the European Union. This contradiction will shape London's negotiations with the European Union over the future of their relationship....