Yunseo Chung was not a visitor. She came to the United States from South Korea at age 7. She was arrested last year for peacefully protesting. Charges against her were dropped but the govt. canceled her green card.
The govt. has been trying to deport her since then, but the courts keep blocking it.
https://humanrightsfirst.org/yunseo-chung-v-trump-administra...
While the legality of these actions are being debated in courts, I think most of us can agree that this is reprehensible behavior on part of the Trump admin.