Alright - I'm at work so I'll have to make this quick.

I talked ot the local USFWS inspector today, and her answer was:
  • Even though Phoca sp. is not endangered, they do fall under the Marine Mammals Protection Act, so new products cannot be imported.
  • Because eBay is involved, these would be considered commercial entries (no matter the size or cost of the shipment), so all of the regulations that we've already discussed would apply.
Now, she did state that if the sporran was a heritage item (family heirloom or the like), and the owner presented a certified letter stating such, then he would be allowed to keep it.
(She actually used the example of ivory on bagpipes, but the principle is the same.)

So - now that we've got the facts straight from the horse's mouth, who wants to tell eBay that this seller is making false claims?
(Or at the bare minimum, let everyone here know not to buy from them.)