Botswana's political landscape is dominated by BDP, which currently controls 54 percent of the assembly, but opposition parties operate freely and are well-represented in the National Assembly, especially the BNF with 37 percent of the Parliamentary seats. The next parliamentary elections are due by October 1999. Botswana follows a republican and presidential variant of ex-colonial British model consitutions, which came into operation at independence in 1966. Its statutory legal system is a mixture of Romano-Dutch and English common law principles. There are also local systems of 'tribal' law and custom in rural district, which govern everyday disputes and property relations but are subordinate to statutory law.
Ultimate sovereignty is vested in parliament through the presidency.
There is also a House of Chiefs, with an advisory role on matters of legislation pertaining to 'tribal' law and custom. The constitution was amended in 1970 so that the president would no longer be an elected member of parliament standing for a constituency. Instead the president would be automatically elected as an ex-officio member and as president in parliamentary elections after prior nomination by the party with the majority of members elected. The president is assisted by a vice-president, who has usually also been minister of finance and development planning. The office of the president oversees foreign affairs, the security forces, and the various branches of administration, while the ministry of finance and development planning generally supervises other line ministries.