Someone in a public business may not discriminate against people based on race, creed or color, etc. Putting a scarlet letter on someone may violate state law but even if not, there are other means of preventing certain persons from bidding on items such as private contact and having eBay bar them participating in any auction. In any event, legal or not, I don't like what that dealer is doing; it is too easy to abuse innocent people. Jim Reilly will tell you about a dealer who was committing outright fraud and whom both of us reported to eBay. He sent me a post saying I was never to bid on any item he therefore put up for auction. We had the last laugh when his eBay account was revoked by eBay.