EBay signed up a lot of sellers, mostly newbies, when they rolled out the GSP.
Most did not know they were enrolled.
This seller does not want to ship internationally.
It would be best to accept his preference and ask him to cancel the transaction.
While you are bound to be disappointed, this is not the seller's responsibility.
It is yet another failing of poorly designed, poorly introduced program.
It's up to you of course, but it would be polite to leave no feedback.
The rollout happened a couple of years ago. It is an indication of how few international sales that US sellers get (and of the strength of the US economy) that this is likely the first non-US sale your seller has ever seen.
