A Brief History of the Middle Ages

In theory, all the soil of the country was held by the king as a fief from God (in practice, the king's title was his good sword), granted on conditions of fealty to right and justice. Should the king be unjust or wicked, he forfeited the kingdom, and it might be taken from him and given to another. According to Papal theorists it was the Pope who, as God's vicar on earth, had the right to pronounce judgment against a king, depose him, and put another in his place.