The study seeks to examine an aspect of the phenomenon of clandestine marriages following the promulgation of canon 51 of Lateran IV. It will explore the production and use of banns, the announcements read publicly before the marriage took place, within diocesan legislation and in the context of the trial between the 12th and 13th centuries. The objective is to ascertain how and to what extent this legal device was formulated and used within medieval legal production.