Legal provisions for optional referendums at national level
Netherlands
Answer
Yes
Source
Wetraadgevend referendum (Consultative Referendum Law) 13-07-2015
http://wetten.overheid.nl/BWBR0036443/geldigheidsdatum_13-07-2015#Hoofdstuk7_Paragraaf2_Artikel44
Comment
The new law has been adopted in Netherlands in 2015, which allows optional referendum initiated by citizens.
