They do give exceptions for "promising young players," but that's more than a little bit subjective. One way to do an end-around on the whole work permit thing is to acquire a second nationality, which players like Friedel and Gregg Berhalter have. It's a little soon to be naturalized, but Ahn could always marry in.
Ahn's case has some other problems. Both Perugia and Busan claimes that they own Ahn. With no real set club, they couldn't give the permit to Ahn.