A person born in the Republic before January 1949, with a parent born in Ireland before March 1922, was entitled to a British passport.
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The United Kingdom's Ireland Act 1949 came into force on 18 April 1949 and recognised the end of the Irish state's status as a British dominion, which had been effected under the Irish Republic of Ireland Act 1948 brought into force in 1949.
Section 5 of the 1949 Act conferred Citizenship of the UK and Colonies (CUKC) on any Irish-born person meeting all the following criteria:
- was born before 6 December 1922 in what became the Republic of Ireland;
- was domiciled outside the Republic of Ireland on 6 December 1922;
- was ordinarily resident outside the Republic of Ireland from 1935 to 1948; and
- was not registered as an Irish citizen under Irish legislation.