I hope to hear some answers as well. I saw a NYT article but of course they excused all other administrations as not using this policy even though it was in existence. However, one article spoke of Obama getting an unfavorable ruling from a judge on this issue. I do not believe we are getting the truth, just propaganda.
I tried the search engines but got nothing but the Leftist take on things, one from a website called the Socialist World Order.
I would like to have some leads and facts so I can ascertain where it all begun. What little I did found indicates this might be a part of the Immigration Law that has never been enforced.
But I will wait and hope someone with more knowledge can explain.
I found this that gives SOME background:
https://www.vox.com/2018/6/11/17443198/children-immigrant-families-separated-parents