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

Lithuania

Answer

Any issue of national importance, except those excluded

Source

REFERENDUMLAW

(Adopted 2002; lastamended 2012)

http://www3.lrs.lt/pls/inter3/dokpaieska.showdoc_e?p_id=437744

Article 5. Consultative (Deliberative)Referendums

Consultative(deliberative) referendums may be held with respect to other issues of utmostimportance to the State and the People, regarding which it is not necessary tohold a mandatory referendum, they are being proposed for a referendum by 300thousand citizens having the right to vote or the Seimas.