From the beginning of the Roman expansion in the Mediterranean Sea in the Third Century B.C., the Roman State became aware of the necessity to protect subjects, friends and allies of Rome against abuses committed by its own citizens : generals and soldiers, provincial governors, publicans and negotiatores. From 170 B.C., senatus consulta and laws of general range are attested, aiming at defending the authority of the Senate in matters of foreign policy, and regulating the activities of the generals and governors. At the same time, some ambitious imperatores introduced themselves to the allies as the true guarantors (auctores) of the measures taken in their favour. This is well illustrated by letters and decrees emanating from Flamininus, the Scipiones, Lucullus, Caesar or Octavian, which all foreshadow the discourse held by the emperors.