In a major compromise, the parties agreed on measures to promote the Irish language, which trade unionists have long opposed to the fear that it will increase nationalist and republican culture to the detriment of their own. In return, the agreement contained provisions to promote Ulster-Scots, traditionally spoken by descendants of Protestants from Scotland to Northern Ireland. Negotiations were also reinforced by commitments in Dublin and London for increased funding for hospitals, schools and other social services in Northern Ireland. On June 23, 1986, DUP politicians occupied the Stormont Parliament Building to protest against the agreement, while 200 supporters protested outside and clashed with police.  DUP politicians were violently dismissed by the police the next day.  On July 10, Paisley and DUP Vice-President Peter Robinson led 4,000 Loyalist supporters to a demonstration in which they „occupied“ the town of Hillsborough. Hillsborough Castle is where the agreement was signed.  On 7 August, Robinson led hundreds of loyalist supporters to an invasion of the village of Clontibret in the Republic of Ireland. The loyalists went back and forth on the main road, destroying property and attacking two Irish policemen (Gardaa) before fleeing across the border. Robinson was arrested and convicted of unlawful assembly.  In 2004, negotiations were held between the two DUP and Sinn Féin governments for an agreement to restore the institutions.
The talks failed, but a document published by governments detailing the changes to the Belfast agreement was known as the „comprehensive agreement.“ However, on 26 September 2005, it was announced that the Provisional Republican Army of Ireland had completely closed its arsenal of weapons and had „taken it out of service“. Nevertheless, many trade unionists, especially the DUP, remained skeptical. Among the loyalist paramilitaries, only the Loyalist Volunteer Force (LVF) had decommissioned all weapons.  Further negotiations took place in October 2006 and resulted in the St Andrews Agreement. Northern Ireland political parties that approved the agreement were also invited to consider the creation of an independent advisory forum, which would represent civil society, with members with expertise on social, cultural, economic and other issues, and would be appointed by both administrations. In 2002, a framework structure was agreed for the North-South Advisory Forum, and in 2006 the Northern Ireland Executive agreed to support its implementation. The agreement came after many years of complex discussions, proposals and compromises. A lot of people have made a great contribution. Tony Blair and Bertie Ahern were the leaders of the United Kingdom and the Republic of Ireland at the time.
The presidency was chaired by U.S. Special Envoy George Mitchell.  These institutional provisions established in these three areas of action are defined in the agreement as „interdependent and interdependent“. In particular, it is found that the functioning of the Northern Ireland Assembly and the North-South Council of Ministers is „so closely linked that the success of individual countries depends on that of the other“ and that participation in the North-South Council of Ministers „is one of the essential tasks assigned to the relevant bodies in Northern Ireland and the Republic of Ireland].