I don't believe they are banned by the government, just eBay. EBay doesn't want to be responsible for deciding what is OK and what isn't so they just ban everything. At least that's how it's been for the last five years or so.
This. They ban more than the sanctions dictate because they just don’t want to deal with it and it protects them legally if something slips through. PayPal bans them too unless they’ve changed their policy recently
Update on this if you are curious. I had a bunch of Cuban coins I wanted to sell, so I listed them in the historical memorabilia category like the other people who are doing it. It went fine and I sold a bunch of them (Cuban coins are popular, which is why I hate that they won't let you sell them). Then today all of my remaining listings were removed. Here's the email they sent me: After reviewing your account, we've had to take the following action: - Some or all of your listings may have been removed. A list of any removed items will be listed further down in this email. - We have credited all associated fees except for the final value fee for your listing(s). The coin you listed originated from Cuba, a country against which the United States is imposing an embargo. Because eBay is a company based within the United States, it and its subsidiaries are bound by the trade restrictions of the United States Government. As a result, we do not allow any products from Cuba regardless of if they were made or brought into the country before the embargo. We appreciate that you chose to utilize our site, but we must ask that you please not relist in this case. Here are the listings we removed: 263381518875 - 1916 Cuba 2 centavos 263390286958 - 1916 Cuba 2 centavos If you have any concerns or questions, click "Help & Contact" at the top of most eBay pages. We appreciate your understanding.