Their research concludes with a large-scale study of the views of local communities in a border region on Brexit. In April 2019, former WTO Director-General and EU Trade Commissioner Pascal Lamy said that “staying in a customs union after Brexit will not solve the Irish border issue… When we leave the internal market, we would re-enter a border whose thickness depends on the degree of regulatory divergence.  “If you build an important physical infrastructure at a politically controversial border, you re-emphasize the context and causes of the conflict,” he said. 30Ebenso Brexit could jeopardize the Common Travel Area (CTA), a special travel zone created after the partition of Ireland in 1922. The CTA guarantees the free movement of nationals of the United Kingdom and Ireland and allows the United Kingdom, to the Republic of Ireland, the Channel Islands and the Isle of Man to cooperate within the framework of the CTA on border policies and practices.67 In 1922, the British government proposed to the Irish Free State to create the CTA because they refused to introduce passport and immigration controls at the Irish border. 68 According to Bernard Ryan, professor of migration law at the University of Leicester, there are three main reasons why successive British and Irish governments have supported these agreements. First, the British authorities consider that an immigration border between the two states is impractical (as this would involve immigration control between Northern Ireland and Great Britain). Secondly, the numerous economic and social links between the United Kingdom and the Republic justify the need for relative freedom of movement between the two states and, finally, the free movement of workers is important for border workers.69 This is where the backstop comes in – insurance to avoid further inspections or new infrastructure at the border – after Brexit. Instead, the agreement found a creative path by allowing a form of co-sovereignty. The Good Friday agreement allowed Northern Irish to identify themselves as Irish, British or both and to have a passport from one or both countries. 4 Does Brexit really threaten the stability of Northern Ireland? To answer this question and assess the role of EU membership in this debate, this paper will first focus on the particularities of Northern Ireland`s political and constitutional context.