The six counties of what would become Northern Ireland opt out of the Irish Free State on December 7, 1922 and become a separate political entity with allegiance to England.

The Irish Free State Constitution Act 1922 (Session 2) is an Act of the Parliament of the United Kingdom, passed in 1922 to enact in UK law the Constitution of the Irish Free State, and to ratify the 1921 Anglo-Irish Treaty formally.

As originally enacted, the Irish Free State Constitution Act 1922 consists of a preamble, five sections (three of which are very brief), and a schedule. The schedule is the text of the Constitution of the Irish Free State (Saorstát Éireann) Act 1922, which had been passed in Ireland by the Third Dáil sitting as a constituent assembly and provisional parliament for the nascent Free State. This Irish Act itself has two schedules, the first being the actual text of the Constitution, and the second the text of the 1921 Treaty, formally the Articles of Agreement for a treaty between Great Britain and Ireland.

The Irish Act had been approved by the Irish constituent assembly on 25 October 25, 1922. The bill for the UK Act is introduced by the Prime Minister Bonar Law into the Parliament of the United Kingdom in November 1922. The bill’s third reading in the House of Commons is on November 30. The Act receives Royal assent on December 5, 1922.

On December 7, 1922, the day after the establishment of the Irish Free State, the Parliament of Northern Ireland addresses King George V requesting its secession from the Irish Free State. The address is unanimous, with the abstentionist Nationalist Party and Sinn Féin members absent. The King replies shortly thereafter to say that he has caused his Ministers and the Government of the Irish Free State to be informed that Northern Ireland is to do so.

After the Statute of Westminster 1931, the UK government recognises the right of the Irish government to amend or repeal the UK act, but in fact the Irish government does not do so until it is formally repealed as spent by the Statute Law Revision Act 2007. The Irish government amends the Irish act in 1933 and the 1937 Constitution of Ireland repeals the entire Free State constitution. The UK Judicial Committee of the Privy Council rules in 1935 that the 1933 Act had implicitly amended the UK Act with respect to the jurisdiction of the Free State. The Supreme Court of Ireland has taken the view that the Free State constitution was enacted by the Irish Act, not by the subsequent UK Act. This reflects the view of popular sovereignty rather than parliamentary sovereignty, with the constitution’s legitimacy ultimately springing from the 1922 Irish general election.