 Each state and major mainland territory has its own parliament — unicameral in the Northern Territory , the ACT and Queensland , and bicameral in the other states . The states are sovereign entities , although subject to certain powers of the Commonwealth as defined by the Constitution . The lower houses are known as the Legislative Assembly ( the House of Assembly in South Australia and Tasmania ) ; the upper houses are known as the Legislative Council . The head of the government in each state is the Premier and in each territory the Chief Minister . The Queen is represented in each state by a Governor ; and in the Northern Territory , the Administrator . In the Commonwealth , the Queen 's representative is the Governor @-@ General . 
