What was veto in Ancient Rome?

Answer 1

The ten Tribunes of the Plebs were each able to impose a veto on legislation in the Senate - this veto invalidated legislation the veto was imposed on.

This was part of the arrangements brought in as the plebs progressively limited the powers of the traditional patrician rulership.

When Augustus was trying to settle the political disorganisation of the Roman revolution, he gave himself the permanent powers of a tribune of the plebs - that is the ability to introduce legislation into the senate, and the power to veto legislation, and effective way of controlling laws selectively on their merits.

Answer 2

During the 482-year period of the Roman Republic magistrates (executive officers of state) of the same rank could veto each other's actions and magistrates of higher rank could veto the actions of magistrates of lower rank. The plebeian tribunes could veto each other's actions and those of any magistrate. The power to veto was related specifically to actions and therefore required the physical presence of the vetoing magistrate or plebeian tribunes to stop the action. Besides the veto of actions, any magistrate or plebeian tribune could veto a senatum consultum. This was a written opinion issued by the senate in response to having been consulted by a consul (on of the two heads of the Republic) on the drafting of bills before submitting them to the vote of the popular assemblies or by a praetor (the chief justice) on the amendment of existing laws . Despite this being meant to be merely advice (the senate was an advisory body, not a legislative one) a negative response by the senate would customarily lead to the abandonment or amendment of a bill. The plebeian tribunes could also veto each other's bills before they were put to the vote of the Plebeian Council. This was the system of checks and balances of power of the Roman Republic which was due to the fact that the Republic did not have a centralised government, like an administration or a cabinet, and each magistrate operated independently within the remit of his office.

Ther demise of the Roman Republic and the creation of rule by emperors, the magistrates ceased to be elected. Some magistracies were abolished and with the remaining ones the magistrates became appointees of the emperor, who was an absolute ruler. The power to veto disappeared.