that was not at all certain yesterday, and even now there's the constant fact that a border agent can decide to be nasty and use this as a pretext to deny you entry, with no real recourse on your part.

as a parallel example, trump recently decided that you could no longer get your visa stamped in a third country (which a lot of indians did as a matter of course, because wait times for an appointment can be very high back home). there was an explicit carve out for people who had already made appointments at some third country embassy, but a lot of those people went to their stamping appointment and not only did not get the renewal but had their existing visa cancelled (which is apparently within the powers of the embassy official), so they could not even return to the US while waiting for an appointment date in their country of residence, and are basically on unpaid leave right now (best case scenario, would not be too shocked if some of them lose their jobs if they are away for too long).