A Line Tribune was a title held by certain members within the Romulan Star Empire.
They were representatives of the High Tribunal who were sent into the field which made its role different compared to that of a Tribune. Individuals who hold the post were officers that were typically chosen from the Romulan Star Navy's Tal Diann. Their purpose was similar to that organizations Legate's in that they observe fleet deployments as well as operations from close proximity. The duties of a Line Tribune were to report anything unusual to the High Tribunal.
These Romulan's were rarely assigned during peacetime but were more of a crisis position and were selected during crisis threats in order to watch over specific wings or Commander's whose actions have been called into question.