In truth, because most humans were believer of Church of the Saints, it was forbidden to sell or turn humans into slaves. Even so, criminals among human race could become trade goods. It was okay to sell or enslave those who betrayed God. However, the trembling children before their eyes couldn’t have possibly fall into such circumstances where they turned into criminals. To begin with, human who turned into slaves with regular procedures would not be sent to an auction. As such, they have been captured and to be sold illegally.