Ask him {her} why he/she can't do a normal on campus swap. There are two things that can happen,

A) he/she ignores you
B) a really long sob story, etc...

With the sob story, its becomes really interesting, because unless the person is a veteran scam artist, there will be holes or a very weak story. Might be fun to show him/her what a looser he/she is for trying to pull such a scam...