The Irish Government cannot introduce legislation in Ireland that conflicts with Bunreacht na hEireann (the basic law or Constitution of the country). Sometimes it is necessary therefore, to change or amend the Constitution.
Each time the Government wishes to change or amend the Constitution, it must do it by holding a referendum. A referendum gives the people of Ireland the opportunity to express their opinion and vote for or against the proposed change or amendment.
In order to call a constitutional referendum, a proposal to amend the Constitution must be introduced in the Dáil as a Bill. The Bill sets out the proposed amendment to the Constitution. The Bill must be passed by both the Dáil and the Seanad.
The Bill is then submitted to the people so that they can vote for or against it. If the majority of the votes cast at the referendum are in favour of the change, the Bill is signed by the Irish President and the Constitution is then amended. Read more about the President and legislation here.
In October 2009, the 28th Amendment of the Irish Constitution (Treaty of Lisbon) Bill 2009 was passed in Ireland's most recent referendum.