According to the constitution of 1959, Tunisia is an Islamic republic, although since independence it has been a thoroughly secular state. The president, who is chief of state, must be a Muslim and a Tunisian citizen, born of a Tunisian father and grandfather, and at least 40 years old. He serves a five-year term. The president enjoys extensive powers, initiating and directing state policy and appointing judges, provincial governors, the mayor of Tunis, and other high officials, The cabinet, headed by a prime minister, varies in size and is under presidential domination.
The unicameral national assembly (Majlis al-Ummah) was expanded in 1993 to 163 members and again in 1997 to 182 members, elected by general, free, direct, and secret ballot. Since 1994 the opposition has been guaranteed a number of seats in the assembly, with the changes introduced in 1997 guaranteeing them 20% of the assembly seats. All citizens 20 years of age or older may vote; candidates must be at least 25 years old and born of a Tunisian father or Tunisian mother. The assembly sits twice a year for five years, but may be extended in the event that a national emergency prevents new elections. Presidential ratification is required before a bill passed by the legislature can become law, but the assembly may override the president's veto by a two-thirds majority. The president may enact decrees in an emergency or when the assembly is in recess.
A series of constitutional amendments were overwhelmingly approved by voters in a 26 May 2002 referendum. Civil liberties were expanded, and human rights were guaranteed. Provisions for a second legislative body, a Chamber of Councilors, were made. Presidential term limits were abolished, and the age limit for a presidential candidate was raised from 70 to 75, thereby making Ben Ali, then age 65, eligible for reelection in 2004 and 2009.