 tribunes, the only true representatives of the people, had the authority to enforce the right of Provocatio, which was a theoretical guarantee of due process, and a precursor to our own habeas corpus. If a magistrate was threatening to take action against a citizen, that citizen could yell "provoco ad populum", which would appeal the magistrate's decision to a tribune. A tribune had to assess the situation, and give the magistrate his approval before the magistrate could carry out the action. Sometimes the tribune brought the case before the College of tribunes or the Plebeian Council for a trial. Any action taken in spite of a valid provocatio was on its face illegal.
