Our aim in this paper is to study the institutional transformation of Byzantium into Constantinople according to the analysis of the subscriptions of imperial laws preserved in the Theodosian Code. Cons- tantinople, before becoming a new imperial capital, was conceived as a foundation to settle Italic veterans from the Sarmatic war (322) in the Roman province of Europa and to commemorate the victory over Licinius in 324. Only later, emperor Constantine considered the old Byzantium to be a suitable location to create an administrative centre for ruling the Eastern provinces of the Empire with loyal officials.