None, Paypal don't give any sh* t about that. The only protection you are having if using paypal is if somebody is using your account without your concent or if the item you received is not what you paid for.
For the seller, you're basically scr*ewd. I just got scammed like this. Paypal didn't even gave me the time to show some proof that I actually gave the right product to the custommer. They just closed my case, and took back the money. The person basically got an item for free, and I was left empty handed.