Very proper. Cancel and re-vet.
The previous visa were vetted by the UN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Well, the UN did not necessarily vet the current batch of USA visas to these countries. So my previous statement is not completely correct.
The UN is the, only (that I now of), agency that vetted the _refugees_ which Obama started bringing in. That would mean those impacted by the Trump ban would probably be a subset the UN vetted people.