Legal provisions for mandatory referendums at national level

Constitution 2007

https://www.constituteproject.org/constitution/Montenegro_2007.pdf

Article 157: Confirmation in the referendum Change of Articles 1, 2, 3,4, 12, 13, 15, 45 and 157 shall be final if minimum three fifths of all thevoters support the change in the national referendum.

Law on Referendum (2001)

http://www.legislationline.org/documents/id/3934

Article 3

The republican referendum must be called for the purpose of a priorpronouncement of citizens on any changes in the status of the country, changesin the form of a government and any changes of frontiers.