The most significant constitutional power that a magistrate could hold was that of "Command" (Imperium), which was held only by consuls and praetors. This gave a magistrate the constitutional authority to issue commands (military or otherwise). Once a magistrate's annual term in office expired, he had to wait ten years before serving in that office again. Since this did create problems for some magistrates, these magistrates occasionally had their command powers extended, which, in effect, allowed them to retain the powers of their office as a promagistrate.