the members of the electoral bodies. Bodies responsible for the implementation of the elections are the State Election Commission, county election commissions, the Election Commission of the City of Zagreb, town and municipal election commissions and polling boards. European Parliament elections Croatia first elected 12 members of the European Parliament (MEPs) in a by-election held after its accession to the EU in 2013. Thereafter, its number of members in the European Parliament was reduced to 11 and the country elected them as part of the regular election in 2014. Reallocation of seats followed Brexit so Croatia have returned to 12 seates in 2019 elections. The elections are regulated by special legislation enacted by the Sabor. Provisions of the legislation are very similar to the parliamentary-election legislation, with the main difference being that the 12 members of the European Parliament are elected in a single constituency encompassing all of Croatia, instead of multiple constituencies used in the parliamentary elections. Referendums A referendum in Croatia can be called by the Parliament or the President on any issue falling within the purview of parliament, or on any other issue the president considers important to the independence, unity and existence of the republic. Since the constitution was amended in 2001, parliament is obligated by the constitution to call for a referendum if signatures of 10 percent of registered Croatian voters are collected. The signatures, by law, must be collected within a 15-day period. Referendums are regulated by Article 87 of the constitution of Croatia which requires that the parliament passes an act on each referendum and that the outcome is binding unless the referendum is called as an advisory referendum. There have been three referendums in modern Croatia: Croatian independence referendum, Croatian European Union membership referendum and Marriage definition referendum, and in all three majority voted in favor. There have been four other public initiatives to collect the support of 10 percent of voters for a referendum, none of which were successful: concerning Croatian cooperation with the International Criminal Tribunal for the former Yugoslavia, concerning accession of Croatia to NATO in 2008, concerning Arbitration Agreement on Croatian-Slovenian border issues in 2009, and concerning Labour Act in 2010. Political campaigns Any Croatian citizen aged 18 or over may become a candidate in presidential, parliamentary or local elections. In order to become an official candidate, 10,000 signatures from Croatian citizens aged 18 or over must be