According to the testimony of Tacitus (Germania), the early Germanic peoples had an elective monarchy already in the 1st century.
“They choose their kings by birth, their generals for merit. These kings have not unlimited or arbitrary power, and the generals do more by example than by authority.”
The Germanic peoples’ traditions of government and law differed from those of the Romans. The Germans gave loyalty to a tribal chief, whereas the Romans belonged to an impersonal state that ruled citizens of many nationalities. Roman law was written and applied to all citizens throughout the Empire, regardless of nationality. At the time of the invasions, Germanic law consisted of unwritten tribal customs that applied only to people of a particular tribe and permitted blood feuds and trial by ordeal.
The duties of the Germanic kings varied from nation to nation; all were expected to be effective warriors, but few seem to have been law-givers like the Roman emperors. The powers of Germanic kings were limited by tribal custom and by their need to win the consent of the assembled leaders of the people for any new policy affecting people’s lives or property. The kings were subject to the customary law, and their role in law enforcement was quite limited compared to the police powers exercised by Roman emperors. The right of people to settle disputes among themselves by blood feud was generally recognized.
Germanic ideas of kingship and law underwent slow modification under the influence of the Christian church and Roman imperial traditions. The church promoted a new model of kingship, that of the biblical Hebrew King David. In the eighth century, to Christianize the traditional religious character of Germanic kingship, the church began to anoint and inaugurate the Germanic kings in liturgical ceremonies similar to those used to consecrate bishops and priests. In time, the secular Germanic practice of selecting kings was combined with new liturgical ceremonies, through which the chosen king was given sacral dignity. According to church theory, the king was chosen for royal office by God; he was called upon to uphold divine law, to defend Christianity, to protect the weak, and to rule justly.