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

Iceland's Constitution (1944, last amended in 2013)

Article 26.

If Althingi has passed a bill, it shall be submitted to the President of the Republic for confirmation not later than two weeks after it has been passed. Such confirmation gives it the force of law. If the President rejects a bill, it shall nevertheless become valid but shall, as soon as circumstances permit, be submitted to a vote by secret ballot of all those eligible to vote, for approval or rejection. The law shall become void if rejected, but otherwise retains its force.

Article 79.

Proposals to amend or supplement this Constitution may be introduced at regular as well as extraordinary sessions of Althingi. If the proposal is adopted, Althingi shall immediately be dissolved and a general election held. If Althingi then passes the resolution unchanged, it shall be confirmed by the President of the Republic and come into force as constitutional law.

If Althingi passes an amendment to the status of the Church under Article 62, it shall be submitted to a vote for approval or rejection by secret ballot of all those eligible to vote.

Article 81.

This Constitutional Law shall enter into force when the Althingi so resolves, provided that the majority of all people in the country having the right to vote have expressed their approval of the Law by secret ballot.