<P> In Westminster systems and most constitutional monarchies, the power to veto legislation by withholding the Royal Assent is a rarely used reserve power of the monarch . In practice, the Crown follows the convention of exercising its prerogative on the advice of its chief advisor, the prime minister . </P> <P> Since the Statute of Westminster (1931), the United Kingdom Parliament may not repeal any Act of the Parliament of the Commonwealth of Australia on the grounds that is repugnant to the laws and interests of the United Kingdom . Other countries in the Commonwealth of Nations (not to be confused with the Commonwealth of Australia), such as Canada and New Zealand, are likewise affected . However, according to the Australian Constitution (sec. 59), the Queen may veto a bill that has been given royal assent by the Governor - General within one year of the legislation being assented to . This power has never been used . The Australian Governor - General himself or herself has, in theory, power to veto, or more technically, withhold assent to, a bill passed by both houses of the Australian Parliament, and contrary to the advice of the prime minister . This may be done without consulting the sovereign as per Section 58 of the constitution: </P> <P> When a proposed law passed by both Houses of the Parliament is presented to the Governor - General for the Queen's assent, he shall declare, according to his discretion, but subject to this Constitution, that he assents in the Queen's name, or that he withholds assent, or that he reserves the law for the Queen's pleasure . The Governor - General may return to the house in which it originated any proposed law so presented to him, and may transmit therewith any amendments which he may recommend, and the Houses may deal with the recommendation . </P> <P> This reserve power is however, constitutionally arguable, and it is difficult to foresee an occasion when such a power would need to be exercised . It is possible that a Governor - general might so act if a bill passed by the Parliament was in violation of the Constitution . One might argue, however, that a government would be hardly likely to present a bill which is so open to rejection . Many of the viceregal reserve powers are untested, because of the brief constitutional history of the Commonwealth of Australia, and the observance of the convention that the head of state acts upon the advice of his or her chief minister . The power may also be used in a situation where the parliament, usually a hung parliament, passes a bill without the blessing of the executive . The governor general on the advice of the executive could withhold consent from the bill thereby preventing its passage into law . </P>

Both the president and congress may veto a bill