US Senator George Mitchell, who led the belfast agreement negotiations, said he believed the creation of a border control system between the Republic of Ireland and Northern Ireland could jeopardise the deal.  Surveys published on 18 February 2019 by Irish Senator Mark Daly and two UNESCO Presidents indicated that the reintroduction of a hard border would lead to the return of violence.     Following the British Parliament`s vote to leave the European Union, all parties stated that they wanted to avoid a hard border in Ireland, in particular because of the historically sensitive nature of the border. Border issues were one of the three priorities negotiated in the proposed withdrawal agreement. Following the UK`s exit from the European Union on 31 January 2020, this border is also the border between the EU and a foreign country. The Brexit withdrawal agreement obliges the UK to maintain an open border in Ireland, so that (in many ways) the de facto border is the Irish Sea between the two islands. Since about 2005, the border has been considered invisible, with little or no physical infrastructure, with security barriers and checkpoints being eliminated as a result of processes introduced by the Good Friday Agreement (or „Belfast Agreement“ signed in 1998).    This agreement has the status of both an international treaty between the United Kingdom and the Republic of Ireland (the Anglo-Irish Agreement) and an agreement between the parties in Northern Ireland (multi-party agreement). The border reaches the sea at two coves: Lough Foyle to the northwest and Carlingford Lough to the east. In the century since Ireland`s independence, she and the United Kingdom have never defined where the border is in these canals.
Both bays are recovered by boats from both nations.  During Britain`s accession to the EU, there was no need to resolve the problem, given that the Common Fisheries Policy (CFP) allowed all EU Member States to fish in the waters of other countries and neighbouring countries still had the right to fish on the coasts of the other party within 12 nautical miles.  There is an article on the joint phase 1 report, in which TUAEU describes their solution to the hard border and the GFA – Ireland must leave the EU. The aim of this document is to show that to find a solution to the Irish border issue arising from Brexit, we must go beyond the simple economic, social and economic threats posed by Brexit in Northern Ireland and in the cross-border relations between Ireland and Northern Ireland.