Students in the medieval universities enjoyed certain exemptions from the jurisdiction of the ordinary civil courts. These privileges were normally safeguarded by a conservator Apostolic, usually a bishop or archbishop appointed by the pope. By the Papal bull "Parens scientiarum" ("Father of the Sciences") (1231), the charter of the University of Paris, Pope Gregory IX authorised the masters, in the event of an outrage committed by anyone upon a scholar and not redressed within fifteen days, to suspend their lectures. This right of cessation of lectures was frequently made use of in conflicts between town and gown. On various occasions, the popes themselves intervened to protect the scholars against encroachments by the local civil authorities. Pope Nicholas IV in 1288 threatened to disrupt the "studium" at Padua unless the municipal authorities repealed within fifteen days ordinances they had framed against scholars. It became quite common for the university to lay its grievances against the city fathers before the Holy See, and its appeal was usually successful. (See The Catholic Encyclopedia for a more in-depth discussion.)