Mariateresa Cellurale, Universidad Externado de Colombia, has published Romani Y Gothi En Italia. La Comunión De Derecho En La República Unida De Justiniano (Romani and Gothi in Italy: The Community of Law in Justinian’s United Republic) in Revista de Derecho Privado, no. 21 (2011). Here is the abstract.
The pragmatica sanctio pro petitione Vigilii of 554 did not extend Justinian’s codes to Italy, but rather reaffirmed more vigorously the obligation to apply such codes which had entered into force since the very moment of their previous transmission sub edictali programmate. The Ostrogoth kings acted as magistrates of the Empire and guardians of Roman law, which was applied as ius commune for Goths and Romans, while at the same time the “national” Goth law remained in force, in accordance to the federative principle that was the basis for the building and expansion of the imperium populi Romani.Download the article from SSRN at the link.