The Master Dominion Pandect for Martial Crisis was a Romulan regulation that was envoked in times of emergencies and allows an officer of the Romulan Star Empire to take command of a starship. It widely known though this Praetorian edict was rarely used.
Former Commander Jenyu invoked this law onboard the Galtizh and quickly took control of the ship. (TOS novel: Probe)
Later in 2376, Folan envoked the Master Pandect for Martial Crisis in order to take control of the science facility at the Caltiskan system. (TNG novel: Forever Dark)