The form of the Government of New South Wales is prescribed in its Constitution, which dates from 1856, although it has been amended many times since then. Since 1901, New South Wales has been a state of the Commonwealth of Australia, and the Australian Constitution regulates its relationship with the Commonwealth. Under the Australian Constitution, New South Wales ceded legislative and judicial supremacy to the Commonwealth, but retained powers in all matters not in conflict with the Commonwealth.
Section 109 of the Australian Constitution provides that, where a State law is inconsistent with a federal law, the federal law prevails (to the extent of the inconsistency). The New South Wales Constitution says: "The Legislature shall, subject to the provisions of the Commonwealth of Australia Constitution Act, have power to make laws for the peace, welfare, and good government of New South Wales in all cases whatsoever." Initially the Australian states retained significant independence. Over time, however, that independence has been greatly eroded by both the proliferation of Commonwealth Law, and the increasing financial domination of the Commonwealth.
New South Wales is governed according to the principles of the Westminster system, a form of parliamentary government based on the model of the United Kingdom. Legislative power rests with the Parliament of New South Wales, which consists of the Queen, represented by the Governor of New South Wales, and the two Houses, the New South Wales Legislative Council (the upper house) and the New South Wales Legislative Assembly (the lower house). Executive power rests formally with the Executive Council, which consists of the Governor and senior ministers.
The Governor, as representative of the Queen, is the formal repository of power, which is exercised by him or her on the advice of the Premier of New South Wales and the Cabinet. The Premier and Ministers are appointed by the Governor, and hold office by virtue of their ability to command the support of a majority of members of the Legislative Assembly. Judicial power is exercised by the Supreme Court of New South Wales and a system of subordinate courts, but the High Court of Australia and other federal courts have overriding jurisdiction on matters which fall under the ambit of the Australian Constitution. New South Wales celebrated the Sesquicentenary of Responsible Government in 2006.