Partition of Ireland
The partition of Ireland () divided the island of Ireland into two distinct jurisdictions, Northern Ireland and Southern Ireland. It took place on 3 May 1921 under the Government of Ireland Act 1920. Today the former is still known as Northern Ireland and forms part of the United Kingdom, while the latter is now a sovereign state also named Ireland and sometimes called the Republic of Ireland.
Republic of Ireland Act 1948
The UK's Ireland Act also gave a legislative guarantee that Northern Ireland would continue to remain a part of the United Kingdom unless the Parliament of Northern Ireland formally expressed a wish to join a United Ireland; this "unionist veto" proved to be controversial during the Act's passage through Westminster, as well as in the Irish state and amongst Northern Ireland's nationalist community. The guarantee was replaced in 1973, when the Parliament of Northern Ireland was abolished, by a new guarantee based on "the consent of the majority of the people of Northern Ireland".