There've been several threads where pay-pal have refused a refund or suspended/cancelled accounts siting that their terms exclude guns, but these seem to be where an actual gun changes hands but there is then a dispute.
Equally when it's a straight forward scam where there is no physical item, they seem to refund the payment,
I wonder if it's the legal knife edge between the "intent to buy" as opposed to actually "buying", if it's a scam you don't technically "purchase" anything so how can it be prohibited