such as the ability to dismiss the prime minister in exceptional cases. Section 3(1) of the Constitution Act states "Every power conferred on the Governor-General by or under any Act is a royal power which is exercisable by the Governor-General on behalf of the Sovereign, and may accordingly be exercised either by the Sovereign in person or by the Governor-General". Government institutions New Zealand's legislative, executive and judicial branches function in accordance with the Constitution Act 1986 and various unwritten conventions, which are derived from the Westminster system. New Zealand has a legislature called the New Zealand Parliament, consisting of the King-in-Parliament and the House of Representatives. According to the principle of parliamentary sovereignty, Parliament may pass any legislation that it wishes. Since 1996, New Zealand has used the mixed-member proportional (MMP) system, which is essentially proportional representation with single member seats (that can affect the proportionality of the House, but only to a limited degree). Seven electorates are currently reserved for members elected on a separate Māori roll. However, Māori may choose to vote in and to run for the non-reserved seats, and several have entered Parliament in this way. The Cabinet, which is responsible to Parliament, exercises executive authority. The Cabinet forms the practical expression of a formal body known as the Executive Council. The prime minister, as the parliamentary leader of the political party or coalition of parties holding or having the support of a majority of seats in the House of Representatives, chairs the Cabinet. Section 6(1) of the Constitution Act 1986 states, "A person may be appointed and may hold office as a member of the Executive Council or as a Minister of the Crown only if that person is a member of Parliament". The prime minister and all other ministers take office upon receiving a warrant by the governor-general; this is based on the principle that all executive power ultimately stems from the sovereign. A government must be able to gain and maintain the support of a majority of the MPs in order to advise the governor-general and sovereign; this is the principle of responsible government. New Zealand's judiciary is a hierarchy consisting of the Supreme Court of New Zealand, the Court of Appeal of New Zealand, the High Court of New Zealand, and the District Courts. These courts are all of general jurisdiction. There are several other courts of specialist jurisdiction, including the