As part of the agreement, the British Parliament repealed the Government of Ireland Act 1920 (which had founded Northern Ireland, divided Ireland and asserted territorial right to the whole of Ireland) and the people of the Republic of Ireland amended Articles 2 and 3 of the Irish Constitution, which asserted a territorial right to Northern Ireland. The main themes addressed by Sunningdale and dealt with in the Belfast Agreement are the principle of self-determination, the recognition of the two national identities, intergovernmental cooperation between the British and Ireland and legal procedures for compulsory power-sharing, such as inter-community voting and the D`Hondt system for appointing ministers to the executive.   Former IRA member and journalist Tommy McKearney says the main difference is the British government`s intention to negotiate a comprehensive agreement including the IRA and the most intransigent unionists.  With regard to the right to self-determination, two qualifications are recorded by the writer Austen Morgan. First, the transfer of territory from one state to another must be done through an international agreement between the British and Irish governments. Second, the population of Northern Ireland can no longer be alone in united Ireland; They need not only the Irish government, but also the people of their neighbouring country, Ireland, to support unity. Mr Morgan also pointed out that, unlike the Irish Act 1949 and the Northern Ireland Constitution Act 1973, drawn up under Sunningdale, the 1998 agreement and the resulting British legislation explicitly provide for the possibility of a unified Ireland.  DUP MP Sammy Wilson told the BBC, however, that he was “delighted… the government is now focusing on the fact that the withdrawal agreement has the potential to do a huge damage to Northern Ireland`s economy in the form of higher prices, job losses, loss of access to our largest market in Gb and, of course, the political consequences of all of this. The agreement was reached between the British and Irish governments as well as eight northern Ireland political parties or groups. Three were representative of unionism: the Ulster Unionist Party, which had led unionism in Ulster since the early 20th century, and two small parties linked to loyalist paramilitaries, the Progressive Unionist Party (linked to the Ulster Volunteer Force (UVF) and the Ulster Democratic Party (the political wing of the Ulster Defence Association (UDA).
Two of them have been widely described as nationalists: the Social Democratic and Labour Party and Sinn Féin, the Republican party affiliated with the Provisional Republican Army.   Apart from these rival traditions, there were two other assemblies, the Inter-Community Alliance Party and the Northern Ireland Women`s Coalition. There was also the Labour coalition. U.S. Senator George J. Mitchell was sent by U.S. President Bill Clinton to chair the talks between parties and groups.  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.