The Constitution of Bermuda came into force on 1 June 1967; it was amended in 1989 and 2003. The head of government is the premier. A cabinet is nominated by the premier and appointed officially by the governor. The legislative branch consists of a bicameral parliament modelled on the Westminster system. The Senate is the upper house, consisting of 11 members appointed by the governor on the advice of the premier and the leader of the opposition. The House of Assembly, or lower house, has 36 members, elected by the eligible voting populace in secret ballot to represent geographically defined constituencies.