The Trump administration policy of separating parents and children who have crossed the border between the United States and Mexico between ports of entry, including those who have come seeking asylum, should be considered cruel and unusual punishment and prohibited by the Eighth Amendment.
The administration’s justification for the policy is as a deterrent. I don’t know whether it will be effective in that regard, but for it to be, it would have to inflict sufficient misery as to discourage people from fleeing violence and persecution or seeking better economic opportunities. One of the few things I can imagine to be more cruel than my child being taken from me and not knowing what had happened to them for weeks or months afterward is imagining the utter trauma and complete sense of loss my child would experience in the same circumstance.