Issues in relation to which referendums are optional at the national level

Bermuda
Referendum Act, 2012 Article 6
http://www.bermudalaws.bm/Laws/Consolidated%20Laws/Referendum%20Act%202012.pdf
Holding of referendum and answer to question
6. (1) Where an Act requires that a referendum be held—
a) the question or questions to be answered at the referendum shall be set out in that Act; and
b) subject to anything to the contrary in that Act, the referendum shall be conducted in accordance with the provisions of this Act.