Irish nationality law is contained in the provisions of the Irish Nationality and Citizenship Acts 1956 to 2004 and in the relevant provisions of the Irish Constitution. A person may be an Irish citizen through birth, descent, marriage to an Irish citizen or through naturalisation. The law grants citizenship to individuals born in Northern Ireland under the same conditions as those born in the Republic of Ireland.
A person born on the island of Ireland on or after 1 January 2005:
A person who is entitled to become an Irish citizen becomes an Irish citizen if:
Dual citizenship is permitted under Irish nationality law.
Ireland previously had a much less diluted application of jus soli (the right to citizenship of the country of birth) which still applies to anyone born on or before 31 December 2004. Although passed in 2001, the applicable law was deemed enacted on 2 December 1999 and provided that anyone born on the island of Ireland is:
The previous legislation was largely replaced by the 1999 changes, which were retroactive in effect. Before 2 December 1999, the distinction between Irish citizenship and entitlement to Irish citizenship rested on the place of birth. Under this regime, any person born on the island of Ireland was:
The provisions of the 1956 Act were, in terms of citizenship by birth, retroactive and replaced the provisions of the previous legislation, the Irish Nationality and Citizenship Act 1935. Under that legislation, those born in Northern Ireland on or after 6 December 1922 did not have an entitlement to Irish citizenship by birth. Citizenship of the Irish Free State was determined under the 1922 constitution, as amended by the Constitution (Amendment No. 26) Act 1935.
Like most countries, Ireland does not normally grant citizenship to the children of diplomats. This does not apply, however, when a diplomat parents a child with an Irish citizen, a British citizen or a permanent resident. In 2001, Ireland enacted a measure which allowed the children of diplomats to register as Irish citizens if they chose to do so; however, this was repealed three years later. The option to register remains for those born to diplomats before 2005.
A person is an Irish citizen by descent if, at the time of his or her birth, at least one of his or her parents was an Irish citizen. Place of birth is not a deciding factor. In cases where at least one parent was an Irish citizen born in the island of Ireland or an Irish citizen resident abroad in the public service, citizenship is automatic and dates from birth. In all other cases citizenship is subject to registration in the Foreign Births Register.