Veto

A veto – Latin for "I forbid" – is the power (used by an officer of the state, for example) to unilaterally stop an official action, especially the enactment of legislation. A veto can be absolute, as for instance in the United Nations Security Council, whose permanent members (China, France, Russia, United Kingdom, United States of America) can block any resolution. Or it can be limited, as in the legislative process of the United States, where a two-thirds vote in both the House and Senate may override a Presidential veto of legislation. A veto gives power only to stop changes, not to adopt them (except for the rare "amendatory veto"). Thus a veto allows its holder to protect the status quo.

The concept of a veto body originated with the Roman consuls and tribunes. Either of the two consuls holding office in a given year could block a military or civil decision by the other; any tribune had the power to unilaterally block legislation passed by the Roman Senate.

The institution of the veto, known to the Romans as the intercessio, was adopted by the Roman Republic in the 6th century BC to enable the tribunes to protect the interests of the plebs (common citizenry) from the encroachments of the patricians, who dominated the Senate. A tribune's veto did not prevent the senate from passing a bill, but meant that it was denied the force of law. The tribunes could also use the veto to prevent a bill from being brought before the plebeian assembly. The consuls also had the power of veto, as decision-making generally required the assent of both consuls. If one disagreed, either could invoke the intercessio to block the action of the other. The veto was an essential component of the Roman conception of power being wielded not only to manage state affairs but to moderate and restrict the power of the state's high officials and institutions.

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.

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