A sample of old & new with English (or Englished) works first: a lot will be in a Bodleian History Reading Room rather than the Law Bod.
The name of a Milanese tenure judge, Obertus de Orto (fl 1150), has become associated with a summary of the feudal system of Langobardia/Lombardy, the Libri Feudorum. As these were appended to Justinian's CJC, Italian feudal law was known to the faculties of universities as these institutions spread across Europe.
Evidence for the operation of feudal laws in other regions also survive. See MA:country tabs in this guide