What caused the problem?
Previously, many families caught sneaking across the border — especially those seeking asylum — were released into the United States while their immigration cases were processed. But in April, Attorney General Jeff Sessions announced that federal prosecutors would now pursue a zero-tolerance policy of criminally prosecuting every adult who illegally crossed the border or tried to do so.
Sending adults to jail for prosecution prompted a set of court-imposed rules stemming from a class-action lawsuit over how the government handled unaccompanied minors in immigration detention. In the Trump administration’s view, the government cannot hold children in immigration detention for over 20 days.
That meant that if adults were sent to jail or long-term indefinite detention while their asylum requests or removal orders were processed, the children could not stay with them. As a result, the Trump policy of prosecuting adults has also led to a practice of separating families and holding children separately while trying to place them with relatives or in a licensed facility.
Courtesy NY Times