The Praetorian Guard was the Roman police force on the planet 892-IV. The Guard served the First Citizen during the tenure of Merikus. They were also responsible for rounding up rebellious or runaway slaves and placing them in the City Prison. Some of them were fans of Empire TV as one of the guards recognized Flavius Maximus when he was captured.
After the capture of the landing party from the USS Enterprise by runaway slave Flavius Maximus, it was recognized that they wore unfamiliar uniforms, causing him to theorize that they must be part of "some new Preatorian Gaurd unit." (TOS: "Bread and Circuses")