plays a central role in debating government ideas as well as scrutinising the government's business and its agenda. However, the opposition's power is limited while the government commands a majority in the Legislative Assembly due to the traditionally strong party discipline throughout Australia. Parties must have at least 500 members on the Victorian electoral roll, have a party constitution and register with the Victorian Electoral Commission to receive official status. The Labor Party has been in Government since 4 December 2014, led by the Premier and leader of the Labor Party in Victoria, Daniel Andrews. The Leader of the Opposition Coalition is Matthew Guy, who was elected as the leader of the Liberal Party on 7 September 2021. He replaced Michael O'Brien as party leader in a leadership spill and became party leader and Leader of the Opposition for the second time. The Greens are led by Samantha Ratnam. Parliamentary sovereignty Parliamentary sovereignty within Australia is a complex matter due to the nature of the monarchy, federation, and the gradual centralisation of power into the federal government over time. Victoria's Parliament is subjected to the limits of the Commonwealth constitution and its powers stem from the Crown. Furthermore, the Commonwealth Parliament has exclusive powers in some matters that the states may not exercise at all. In matters where the powers of the Victorian and federal parliaments overlap, the federal parliament's powers prevail. There are no other restrictions to Parliament's authority, though, and the largely ceremonial role the crown has in governance makes Victoria's parliament sovereign over Victoria in practice. Such power is nonetheless approved by the governor whose power stems from the monarch. Parliament's sovereign power over Victoria is supreme when compared to the equivalent federal parliament's power over Australia as a whole; Victoria's Constitution does not rigidly define a separation of powers as the Commonwealth's constitution does, meaning that all powers residing within the executive and judicial branches of government stem from Parliament. There is no legal impediment, therefore, to Parliament exercising control over the other branches of government. Parliamentary sovereignty was legally tested following the passage of the Victorian Charter of Human Rights and Responsibilities 2006, which delegated powers to the judiciary to oversee human rights violations within Victoria. Although this allows the judiciary to intervene in Parliament's role in certain circumstances, subsequent legal analyses have determined that the courts only have such power as they have been