Who can initiate an optional referendum at the national level?

Constitutionof 2014

https://www.constituteproject.org/constitution/Tunisia_2014.pdf

Article 82: Referendum power

The President of the Republic may, in exceptionalcircumstances, within the deadlines for return of a draft law, submit for areferendum draft laws related to the ratification of treaties, to freedoms andhuman rights, or personal status, which were adopted by the Assembly of theRepresentatives of the People. The submission to referendum shall be deemed awaiver of the right to return the draft law to the Assembly.

If the result of the referendum is the ratification ofthe draft law, the President of the Republic shall sign it and order to publishit within a period not exceeding ten days from the date of announcement of theresults of the referendum.

The election law shall regulate the procedures for conductingthe referendum and announcing its results.