Conflicts over independance in Ireland
The issue of self-governance or independence in Northern Ireland goes back a long way. In the 17th century, the whole of Ireland was part of the UK and was ruled from London. In 1641, the nine counties from the North of Ireland (also known as Ulster) were annexed by the British Crown. English and Scottish Protestants colonised the region which was originally Catholic. Many conflicts arose from this situation.
In the beginning of the 20th century, Westminster initiated legislation to grant Ireland independence (sometimes called Home Rule), but the outbreak of World War I interrupted the process. In 1916, the Easter Uprising was a revolutionary attempt to grant Ireland independence, but it was crushed by the British who executed all the leaders of the movement. In 1919, the Catholic nationalist movement, Sinn Fein, proclaimed independence once again and started a terrorist campaign against the British forces on Irish soil.
The independance of Southern Ireland
In 1920, the Government of Ireland Act led to the partition of Ireland that took place in 1921: Southern Ireland and Northern Ireland. The Irish Free State Agreement Act of 1921 made Ireland independent, and the country was renamed Eire (Irish Gaelic for Ireland) in 1937 when it became sovereign, independent and democratic. The country became the Republic of Ireland in 1949.
Home Rule in Northern Ireland
This is how Northern Ireland experienced "Home Rule" from 1921 onwards. Indeed, Northern Ireland was part of the UK but had its own separate devolved parliament. It had power over domestic affairs and could vote its own legislation, except for defence and foreign policy, still in the hands of London. The original Northern Ireland Parliament was in Stormont, near Belfast. It was suspended in 1972 after the Bloody Sunday events.
After much armed conflict, including "The Troubles", a referendum was held in 1998 in both Northern Ireland and the Republic of Ireland which led to the ratification of the Good Friday Agreement. The Northern Ireland Assembly was established in 1998 and has powers over domestic affairs only, and not on issues regarding criminal justice, prisons, policing and security matters in general.