`In aliquibus locis est consuetudo': French Lawyers and the Lombard Customs of Fiefs in the Mid-Thirteenth Century

Jean de Blanot, the enigmatic Iacobus Aurelianus, and Jean Blanc de Marseille are the first known French lawyers trained in Italy to have shown interest in one of the most famous custumals in medieval Europe, the Lombard book of fiefs known by the name of Libri Feudorum. Considering that this compilation was increasingly gaining authority in the Italian law schools, this chapter shows how these three lawyers re-elaborated these teachings and compared (or opposed) them to local bodies of norms. By observing how they developed different notions of custom and argued about the validity of the Libri Feudorum outside Lombardy, the chapter unveils the problematic dialectics between Civil law, local custom, and practice, and provides some insights into the making of the ius commune, its practical and historical roots, its geographical dimensions.