Posted By:
JoshI would think decertifying the serial number is equivalent to theft. At some point in time, someone paid $10-50 to have that card graded/authenticated, with the primary purpose being to add value to the card, which PSA declares is one of their main offerings in their business statement. By decertifying, they have theoretically removed nearly the entire value of their service.
PSA didn't have a leg to stand on in asking for the card to be returned, but the seller is quite the dirty one himself, for refusing to turn the card over, and instead attempting to bilk someone for money that was never entitled to him in the first place.