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

Kazakhstan
- Constitutional amendments
- Any issue of national importance, except those excluded
Law on Referendum (1995, last amended in 2008)
http://aceproject.org/ero-en/regions/asia/KZ/kazakhstan-constitutional-law-on-referenum-1995/view
Article 2. Subject of the republican referendum
The subject of referendum shall be:
1) adoption of the Constitution, constitutional acts,laws of the Republic, introduction to them of any changes and additions;
2) solution of other most important issues of the public life of theRepublic.