The two main political parties in the agreement were the Ulster Unionist Party (UUP), led by David Trimble, and the Social Democratic and Labour Party (SDLP), led by John Hume. The two heads of state and government together won the Nobel Peace Prize in 1998. The other parties to the agreement were Sinn Féin, the Alliance Party and the Progressive Unionist Party. The Democratic Unionist Party (DUP), which later became the largest Unionist party, did not support the agreement. When Sinn Féin and loyalist parties entered, they left the talks because republican and loyalist paramilitary weapons had not been decommissioned. With regard to the constitutional question of whether Northern Ireland should remain in the United Kingdom or whether it should be part of a unified Ireland, it was agreed that there would be no change without the agreement of the majority. This is called the “consent principle.” Majority opinion could be tested by referendum in the future. 2 There is a general consensus that the UK`s exit from the European Union will have a negative impact on the Irish and Northern Irish economies, as well as on cross-border trade and relations between Ireland and Northern Ireland, particularly in certain sectors that are heavily dependent on such trade, such as the agri-food sectors. However, if a general agreement has still not been reached between the political parties London, Brussels, Dublin and Northern Ireland on the status of the Irish border after Brexit, it is not only because of these potentially negative socio-economic effects. This is mainly due to the fact that the current soft border system is an integral part of a very complex constitutional and institutional order, created by the 1998 Good Friday Agreement (GFA) and ratified by two simultaneous referendums in Ireland and Northern Ireland. Therefore, it can rightly be argued that the reason the Irish border is so controversial today is because the GFA has not provided a real and consensual solution to the unwelcome question of the very status of the Irish border.
Despite 20 years of peace and a 56% majority in Northern Ireland in favour of remaining in the EU, northern Ireland`s Unionist and Nationalist nationals still do not agree on what will happen to this border. In other words, if Brexit raises several problems and debates on the Irish border issue, it is not so much the consequence of Brexit itself as a symptom of the initial weaknesses of the Good Friday Agreement (GFA).