Behind paywall, so I can’t see the real reason they picked him up.
Summary, please.
The only reason given in the article was that ICE picked him up as an alien.
He came to the US with his parents, but the point is that the parents and he, as a child, all came here legally, the US let them in. They did not sneak across the border.
So it is terrible that ICE would arrest him.
I think the article is trying to equate this serious bungle by ICE with their legitimate activities of deporting real illegals, who really came to the US illegally.