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

Venezuela
- Transfer of authority to international bodies
- National sovereignty, national self-determination
- Any issue of national importance, except those excluded
- Any bill being discussed by the Legislature
Constitution ofVenezuela (1999)
http://venezuelanalysis.com/constitution/
Article 71: Matters of special nationaltranscendence may be referred to a consultative referendum, on the initiativeof the President of the Republic, taken at a meeting of the Cabinet; byresolution of the National Assembly, passed by a majority vote; or at therequest of a number of voters constituting at least 10% of all votersregistered on the national, civil and electoral registry.
Matters of special state, municipal and parishtranscendence may also be referred to a consultative referendum. The initiativeshall be taken by the Parish Board, the Municipal Council and to theLegislative Council, by the vote of two third of its members; by the Mayor andthe Governor or by a number of voters constituting at least 10% of the totalnumber of voters registered in the pertinent circumscription.
Article 73: Bills under discussion by theNational Assembly shall be submitted to a referendum when at least two-thirdsof the members of the Assembly so decide. If the referendum ends in anaffirmative vote of approval, provided that the 25% of the voters registeredbefore the Civil and Electoral Registry have concurred to the election, thebill conceded shall be enacted into law.
Any international agreement, convention or treaty whichmight compromise the national sovereignty or transfer authority tosupranational organs, may be submitted to a referendum on the initiative of thePresident of the Republic, taken at a meeting of the Cabinet by a two-thirdsvote of the members of the Assembly or by 15% of the voters registered on thecivil and electoral registry.
Article 74: Statutes whose abrogation arerequested on the initiative of a number of voters constituting at least 10% ofthe voters registered in the civil and electoral registry, or by the Presidentof the Republic taken at a meeting of the Cabinet, shall be submitted to areferendum for its abrogation in whole or in part.
Decrees with the force of law issued by the President ofthe Republic, making use of the authority prescribed under article 236, section8 of this Constitution, may also be submitted to an abrogatory referendum, whenit is requested by a number of voters constituting at least 5% of the totalnumber of voters registered in the civil and electoral registry. In order forthe abrogatory referendum to be valid, a number of voters constituting at least40% of the total number of voters registered in the civil and electoralregistry shall be essential.
It shall not be possible to submit budget laws to anabrogatory referendum, neither those establishing or modifying taxes, relatingto public credit, to amnesty, the protection, guaranteeing and developing humanrights, nor those which ratify international treaties.
There shall not be more than one abrogatory referendum onthe same matter during the same constitutional term.
Article 345: The constitutionalreform shall be declared approved if the number of affirmative votes is greaterthan the number of negative votes. A revised constitutional reform initiativemay not be submitted during the same constitutional term of office of theNational Assembly.