Unfortunately paypal can't do much if anything about it, the bank that issues the CC makes the determination if a chargeback is valid or not and their only interest is in keeping their customer happy. As long as the customer isn't to far out in left field the charge back will go through. Paypal can't win a lot of the charge back cases.
Your best option is to refuse CC payments or accept the risk of chargebacks unfortunately. It might also help to limit purchases to certain countries and or require phone verification of the order.