Quorum requirements for a referendum to be valid

Ireland, Constitution (1937, as amended in 2019), accessed 14 September 2022

ARTICLE 47.

1. Every proposal for an amendment of this Constitution which is submitted by Referendum to the decision of the people shall, for the purpose of Article 46 of this Constitution, be held to have been approved by the people, if, upon having been so submitted, a majority of the votes cast at such Referendum shall have been cast in favour of its enactment into law.

2.1 Every proposal, other than a proposal to amend the Constitution, which is submitted by Referendum to the decision of the people shall be held to have been vetoed by the people if a majority of the votes cast at such Referendum shall have been cast against its enactment into law and if the votes so cast against its enactment into law shall have amounted to not less than thirty-three and one-third per cent of the voters on the register.

2.2 Every proposal, other than a proposal to amend the Constitution, which is submitted by Referendum to the decision of the people shall for the purposes of Article 27 hereof be held to have been approved by the people unless vetoed by them in accordance with the provisions of the foregoing sub-section of this section. […]

Mandatory referendum - no quorums requirements. Optional referendum - 1/3 of of the voters on the register.