Optional referendum
The second category of referendum is the optional referendum. These are referendums which do not by law have to be held, but can be initiated by the government, and in some cases by other parties. Optional referendums may or may not be binding.
A government can decide to initiate a referendum on a major political issue. It might do so because public pressure for a referendum forces it to hold one, or it might choose to hold a referendum because it is divided on the issue at hand. Optional referendums initiated by the government have been held frequently in Europe on the issue of European Union integration (although in some cases, such referendums have been mandatory because they involve an amendment to a country's constitution). These referendums may not be legally binding, although it may be politically difficult for a government to ignore the outcome.
In addition, in some countries, Parliament or a Parliamentary minority may also be able to call a referendum.
A further type of optional referendum is the abrogative referendum. Abrogative referendums are held when citizens force a vote on a piece of new law passed by the legislature, usually by collecting a certain number of signatures in support of a vote, see citizen initiatives. In some countries, abrogative referendums can also be used in relation to existing legislation. If the law is defeated in a vote on the issue, it may be required to be repealed or amended.