Along with a simple majority required for the proposal to be passed, Article 208 provides for an approval quorum when the referendum concerns the issues of sovereignty and the form of government (half of the registered voters, see Article 142(1) of the Constitution) and the dismissal of the President or a mayor (equal or a greater number of voters that elected the President/mayor but no less than half of the voters who cast ballots in the referendum). Moreover, a one-third participation quorum is required for a constitutional, legislative or local referendum to be valid (Articles 211 and 240). The Code of Good Practice on Referendums notes that introducing an approval quorum for referendums on matters of fundamental constitutional significance is acceptable but advises against a turnout quorum as it encourages disengagement campaigns and may lead to failed referendums, frequently observed in Europe. ODIHR and the Venice Commission recommend reviewing referendum quorum requirements.