On 21 June 2002, the Irish Government made a National Declaration at the Seville European Council emphasising its commitment to the European Union's security and defence policy.
After the first failed Irish referendum on the Treaty of Nice, EU Leaders met to discuss the outcome of the Irish Referendum in Seville (Spanish Presidency of the Council of the European Union.) Out of the meeting came declarations known as the Seville Declarations on the Treaty of Nice
At the Seville European Council (21–22 June 2002) the other EU14 governments accepted an Irish declaration that spelled out the triple lock - UN mandate; cabinet approval; Dáil Éireann approval - on Irish participation in EU activities of a military nature. The triple lock was nothing new as the Government never deployed Irish defence forces without UN approval to maintain Military neutrality, and moreover the declaration had no legal status, so this measure on the part of the Irish government must be understood primarily as a political signal to the Irish electorate. In response to the Irish declaration, the European Council issued a declaration of its own. It recognised the right of Ireland (and all other member states) to decide in accordance with National Constitutions and laws whether and how to participate in any activities under the European Security and Defence Policy.
It led to the second Irish referendum on the Treaty of Nice.