Mistakes of this nature are unacceptable, even with a high volume of deportations. They trafficked a person who was very credibly neither a gang member nor a criminal to the Salvadoran government despite a standing court order not to deport him. People should go to jail for this.
He was caught with other gang members and a reliable witness according to the DOJ said he was a gang member. An immigration judge came to the conclusion he was one as well.
It's difficult to determine who's a gang member. They aren't going to admit to it and they don't have special decoder rings that say they are one.