This is a small collection of the surviving correspondence of Pope Leo IV, bishops of Rome. In a synodal council held in Rome, Pope Leo IV and Emperor Lothair addressed ongoing disputes between the bishops of Siena and Aretine regarding jurisdiction over parishes and dioceses. Bishop Cantius of Siena presented evidence of territorial invasions by Peter, bishop of Aretine, prompting the council to reaffirm the importance of canonical authority and the need for peace within the Church. The decree emphasized that bishops must respect territorial boundaries and not encroach upon one another's jurisdictions, reinforcing the necessity of unity and adherence to ecclesiastical law to prevent discord among the faithful.