You're only allowed to if you're form a country like China. Which pisses me off, because how are genuine sellers suppose to compete with that? If they're going to allow it they should allow it for everyone. Or not allow it at all, but I believe in freedom so I say allow it, but for everyone. Perhaps put a requirement that you MUST state it's not the real thing. A lot of the time people actually want the real thing but trying to search Ebay/Amazon is a gamble as you don't know what you're getting. So I say allow it, but require that it needs to be marked.
Same with ULC approvals etc on electronic stuff. China is allowed to sell stuff that has zero safety recognition but if you want to try to sell something then it has to be certified. The cost of doing that makes it not worth it. The system is pretty much designed to prevent locals from having a chance. They government even went as far as cutting trade deals that make it so shipments from China are free.
These rules are not the site's (Ebay and Amazon etc) jurisdiction but the government. The sites just have to follow the rules that the government laid out by not allowing certain items or allowing certain items.