Fifteen years after the establishment of the Roman Republic, the plebeians were burdened by crushing debt and unemployment. A series of clashes between the people and the ruling patricians in 495 and 494 BCE brought the plebeians to the brink of revolt. In an act of mass protest the plebeians seceded en masse to the Mons Sacer, a hill outside of Rome. Panicked by this turn of events, the senate dispatched Agrippa Menenius Lanatus, a former consul who was well-liked by the plebeians. Menenius was well-received, and he explained that Rome could not survive without both the patricians and plebeians working in concert. The plebeians agreed to negotiate their return to the city; and their condition was that special tribunes should be appointed to represent the plebeians, and to protect them. In formoation of this office the tribunes were to be sacrosanct; any person who laid hands on one of the tribunes would be outlawed, and the whole body of the plebeians entitled to kill such person without fear of penalty. The senate agreeing to these terms, the people returned to the city.
As plebeian magistrates, the tribunes were elected by the plebeian assembly alone. They could convene the concilium plebis, which was entitled to pass legislation (plebiscita). The tribunes were entitled to propose legislation before this assembly.
Intercessio, was the power of the tribunes to intercede on behalf of the plebeians and veto the actions of the magistrates. Being sacrosanct, no person could harm the tribunes or interfere with their activities, doing so was regarded a violation of their sacrosanctity. This sacrosanctity also made the tribunes independent of all magistrates; no magistrate could veto the action of a tribune. Only a dictator was exempted from the veto power. 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, ego te provoco! 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. 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.Within the Modern Res publica:
The Tribunes of the Plebs are charged with monitoring the activities of all magistrates. They are also to insure the protection of citizens from injustice. In this capacity they represent the citizens. They may also oppose all proposed legislation and edicts which are deemed not in the interest of the people. In order to insure transparency the tribunes may attend all meetings of the senate and are to publically issue reports summerizing the minutes meetings
All Tribunes may issue a veto (intercessio) against any magistrate. This veto expires unless the Concilium Plebis ratifies any veto issued making it permanent. No magistrate may veto the activites of the Tribunes.The Concilium Plebis elects the Tribunes from citizens who belong to the plebeian order.