When the Nice Treaty was put to a second vote, the wording of the constitutional amendment excluded participation in common defence.

The Government of Ireland and the European Council jointly made the Seville Declarations on the Treaty of Nice in June 2002 to recommit themselves to shared interests ahead of the second vote.

The Twenty-sixth Amendment permitted the Republic to choose to exercise these options, provided its decision was approved by the Oireachtas.

The Twenty-sixth Amendment of the Constitution Bill was proposed in Dáil Éireann by Minister for Foreign Affairs Brian Cowen on 4 September 2002 on behalf of the Fianna Fáil–Progressive Democrats coalition government led by Taoiseach Bertie Ahern.

This is because the Twenty-fourth and Twenty-fifth Amendment of the Constitution Bills were both rejected in referendums, and the government decided not to reuse the numbers.