It looks like Etsy's policy is a little more explicit about it being the seller's job to make sure whatever it is is legal wherever it is.
> Due to the potential harm caused by hazardous materials, as well as complex legal regulations surrounding such materials, including shipping restrictions, hazardous materials are prohibited on Etsy
Etsy doesn't define "hazardous materials" in their policy though, just provides a few examples.
> Our marketplaces provides a direct connection between buyers and sellers around the world. If you buy or sell an item from another country, or if you enter into a transaction with someone across international borders, you are responsible for complying with international trade restrictions, including restrictions put into place by the US Office of Foreign Assets Control (“OFAC”), regardless of your location.