Northern Ireland national football team
In 1920, Ireland was partitioned into Northern Ireland and Southern Ireland. In 1922, Southern Ireland gained independence as the Irish Free State, later to become a republic under the name of Ireland. Amid these political upheavals, a rival football association, the Football Association of Ireland, emerged in Dublin in 1921 and organised a separate league and international team. In 1923, at a time when the home nations had withdrawn from FIFA, the FAI was recognised by FIFA as the governing body of the Irish Free State on the condition that it changed its name to the Football Association of the Irish Free State. The Irish FA continued to organise its national team on an all-Ireland basis.
Northern Ireland Constitution Act 1973
When the Republic of Ireland ceased to be a member of the British Commonwealth, Westminster had responded with the Ireland Act 1949. Amongst its other provisions, the Act had guaranteed that Northern Ireland would not cease to remain a part of the United Kingdom "without the consent of the Parliament of Northern Ireland" (s. 1(2)); this declaration had proven to be controversial both with the Irish government and with Northern Ireland's nationalist community.