Aim of the contribute is to offer a new key to analyse the matter concerning the influence of Byzantine law sources on the development of the legal system in Southern Italy. In addition to a historical and juridical survey about the reception process of the Isaurian Ekloge in the territories controlled by the Byzantines, a comparison is tried considering the diffusion of the compilation also in the Slavian world and especially in the Balkan regions: to study the reasons, which persuaded Stefan Du{an to use the text to compose his Zakonik, could be very useful to understand the characters - totally different because of political grounds - of the preservation of the Isaurian Ekloge in the manuscripts coming from Southern Italy.