Legal provisions for mandatory referendums at national level

Switzerland
Answer
Yes
Source
FEDERAL CONSTITUTION OF THE SWISSCONFEDERATION
(Adopted1999; last amended 2013)
http://www.admin.ch/ch/e/rs/c101.html
Art. 140 Mandatory referendum
(1) The following must be put to the vote of thePeople and the Cantons:
- amendments to the Federal Constitution;
- accession to organisations for collective security or to supranational communities;
- emergency federal acts that are not based on a provision of the Constitution and whose term of validity exceeds one year; such federal acts must be put to the vote within one year of being passed by the Federal Assembly.
(2) The following are submitted to a vote of thePeople:
- popular initiatives for a complete revision of the Federal Constitution;
- popular initiatives for a partial revision of the Federal Constitution in the form of a general proposal that have been rejected by the Federal Assembly;
- the question of whether a complete revision of the Federal Constitution should be carried out, in the event that there is disagreement between the two Councils.