Except in the case of exceptional circumstances, any department or agency of the Federal Government that has an unaccompanied alien child in custody shall transfer the custody of such child to the Secretary of Health and Human Services not later than 72 hours after determining that such child is an unaccompanied alien child.
You can read the dates at the bottom of those pages. The very latest one youll find on any law written on either of those pages is 2013, well before Trump was elected.
Laws do not equal enforcement. Still haven't seen evidence of past administrations on purposely separating children from parents. ---