or any other assembly disregarded the orders of a tribune, he could "interpose the sacrosanctity of his person" to prevent such action. Only a dictator (or perhaps an interrex) was exempted from the veto power. The tribunes could veto acts of the Roman senate. The tribune Tiberius Sempronius Gracchus imposed his veto on all government functions in 133 BC, when the senate attempted to block his agrarian reforms by imposing the veto of another tribune. Tribunes also possessed the authority to enforce the right of provocatio ad populum, a precursor of the modern right of habeas corpus. This entitled a citizen to appeal the actions of a magistrate by shouting appello tribunos! ("I call upon the tribunes") or provoco ad populum! ("I appeal to the people"). Once invoked, this right required one of the tribunes to assess the situation, and determine the lawfulness of the magistrate's action. Any action taken in defiance of this right was illegal on its face. In effect, this gave the tribunes of the people unprecedented power to protect individuals from the arbitrary exercise of state power, and afforded Roman citizens a degree of liberty unequalled in the ancient world. If the tribune decided to act, he would impose his ius intercessionis ("right of intercession"). Limitations Although a tribune could veto any action of the magistrates, senate, or other assemblies, he had to be physically present in order to do so. Because the sacrosanctity of the tribunes depended on the oath of the plebeians to defend them, their powers were limited to the boundaries of the city of Rome. A tribune traveling abroad could not rely on his authority to intervene on behalf of the plebeians. For this reason, the activities of the tribunes were normally confined to the city itself, and a one-mile radius beyond. History The tribunes in the conflict of the orders In 471 BC the Lex Publilia transferred the election of the tribunes from comitia curiata to the comitia tributa, thus removing the influence of the patricians on their election. In 462, the tribune Gaius Terentillius Arsa alleged that the consular government had become even more oppressive than the monarchy that it had replaced. He urged the passage of a law appointing five commissioners to define and limit the powers of the consuls. By threat of war and plague, the issue was postponed for five contentious years, with the same college of