Not Foreigners, Not a Foreign Country
Although most of Ireland became an independent state in 1922, it was as a dominion of the British Empire known as the Irish Free State. This came to an end in 1937 following a referendum on a new constitution, but some powers were still reserved to the United Kingdom. The final vestiges of constitutional attachment to the United Kingdom were only brought to an end when the Irish passed the Republic of Ireland Act, 1948.
In response to this, the United Kingdom Government passed the Ireland Act, 1949. Section 2(1) of this Act is particularly interesting.
Read @ Syniadau