III defines that of the Judiciary. In addition to the document's text, Australian constitutional law is affected by the structure of the document. The division of the three branches of government into chapters is understood to establish a Separation of Powers doctrine in Australia. It is also known that a number of unwritten constitutional conventions are present within the document. E.g. the constitutional doctrines of responsible government, and the requirement of the governor-general to accept the advice of the prime minister. The Australian constitution is notable for not containing a bill of rights, and express constitutional restrictions upon Commonwealth power are minimal in number and scope. Nevertheless, some restrictions upon Commonwealth power have been recognized by implications drawn constitutional sections unconcerned with the establishment of rights. The stipulations of Section 7 and 24 that the members of the respective Commonwealth legislatures be 'directly chosen by the people'; have been interpreted by the High Court as giving rise to doctrines protecting freedom of political communication, and a right to vote. The constitution may only be amended by a national referendum, a provision inspired by the Swiss Canton system. The respective state governments of Australia also have constitutional documents, many of which have carried over from the colonial era. Those documents, however, are amenable to state legislation, and thus do not bind on the respective state parliaments in the same way that the Commonwealth and the States are bound by Australia's written constitution as supreme law. (see also: Marbury v. Madison) Statute law The legislative powers of the federal Parliament are limited to those set out under an enumerated list of subject matters in the Constitution. These powers include a power to legislate on matters "incidental" to the other powers. The Parliament of the Commonwealth can also legislate on matters referred to it by the Parliament of one or more States. In contrast, with a few exceptions the State legislatures generally have plenary power to enact laws on any subject. However, federal laws prevail in the event of collision, according to Section 109 of the Constitution of Australia. The process of creating a statute involves a Bill being drafted, usually by Parliamentary Counsel. The Bill is read, debated and sometimes amended in both houses of parliament before being approved. Once a bill has been passed it must be assented to by the representative of the sovereign. Legislation may also be delegated to