@Bansri,
During the Roman Republic magistrate held a power called coercitio. By this
power he could compel a citizen to obey his decrees. If the citizen refused,
the magistrate could impose punishment. As a balance to this, the citizen had
the right of provocatio. If he exercised this right by declaring "provoco ad
populum", then a tribune would intervene. The magistration could not carry
out the punishment (including capital punishment) until the tribune made his
decision.