So are they able to be detained, or free to roam?
I think the only way to circumvent this immediately is to void all visas and refugee status from affected countries that are not in transit. Of course the ACLU will seek another court order. This will get sticky.
As I understand the judge’s “emergency stay” order, they don’t have to be released but they can’t be sent back to their countries, either, pending further judicial rulings.
So if there continued to be new arrivals in the coming hours and days, they could be detained, but of course everyone should want that situation resolved quickly, I would hope.
I do not see why the EO should apply to existing visas & green cards, but I’m no lawyer or diplomat.