Originally Posted by
SingaporeDon
How will US CBP know for sure if the ESTA holder has visited one of the "problem" countries to revoke his existing ESTA authorization?
Depends on what data they have. For example visiting USA on a RTW ticket that includes one of the "problem" countries may mean they have this info from PNR data.
Originally Posted by
akb8812
Still valid here.
Surely this will then be a two year process, until the newest applications expire.
Yes for new ESTAs, however USA has said some ESTAs will be revoked (i.e. cancelled). Revoked ESTAs will only occur for some?/all? of those that have visited the "problem" countries - if you haven't visited then won't be revoked.