In a plebiscite held on 1 July 1937 the people enacted a new Constitution, Bunreacht na hÉireann, to replace the 1922 Constitution of the Irish Free State.
Even though the 1922 Constitution had been approved by Dáil Éireann, there continued to exist throughout the country a substantial body of opposition to it owing to its being circumscribed by the terms of the Treaty, its recognition of the British monarch as part of the national legislature and its requirement that members of the Oireachtas swear an oath of faithfulness to that monarch.
Much of the case for a new Constitution was the need to make perfectly clear that the source of authority in Ireland and of the fundamental law of the state is the people of Ireland. Hence the Preamble to Bunreacht na hÉireann says: 'We, the people of Éire,...do hereby adopt, enact, and give to ourselves this Constitution'. There was a desire to give the state all the characteristics of a republic (and so all references to the British monarch were removed).
There also seemed to be a desire to strengthen or entrench the rights of the citizen as against the state. It had been possible to amend the Constitution of the Irish Free State by a simple Act of the Oireachtas without recourse to the people in a referendum.
The proposal to adopt Bunreacht na hÉireann was carried by 685,105 votes in favour to 526,945 votes against, a majority of 158,160.