Like others have said, report him to ebay. That is a violation of policies and would get him kicked off.
I just dealt with a seller (zikster_ii) this last week who after the auction ended sent me an invoice that included sales tax. Now I live in Oregon and we don't have sales tax so I sent him a message letting him know that and asking them to revise the invoice appropriately. They responded back saying that while they don't like paying taxes either but they have to and won't change the invoice. After going back and forth a couple of times (all on the ebay system) with the seller refusing to change the invoice, I contacted Ebay. The Ebay rep did a quick search and found that I was indeed correct and said that I could just pay it then follow up with a dispute or I could send a message to the seller asking them to cancel the sale. I said I would ask for them to cancel it since they weren't listening to me and I no longer trusted them. I sent the seller a message saying that I had contacted Ebay and with their permission, I was asking the seller to cancel the transaction. The next day the seller sent me a new invoice using google checkout and sent me a message outside of Ebay's system saying that they would this 1 time take the hit on the taxes to get this resolved (they still wouldn't check and see that Oregon residents don't have to pay sales tax). They added that if I didn't pay that was they would report me to Ebay. I responded back saying very directly that since they had not listened to me about the taxes I was not going to pay and that I had already spoken to Ebay and it was their suggestion that I asked the seller to cancel the auction. I then copied their message and my response into another message from the Ebay system so that there would be a record that Ebay could see as necessary. The seller's response was very nasty saying a number of rude things about me...again outside Ebay's system. I contacted Ebay again and showed them the latest message. They filled a personal complaint against the seller for me due to the last message. They also had me reported the listing for not following listing guidelines (due to it just saying "follow local tax laws" when the seller wasn't following them), and they had me forward the original invoice received to them at firstname.lastname@example.org. The department responded back and said that invoice was indeed a fake because one submitted through there system would have not had any sales tax for Oregon.
This was not a brand new seller. This person currently has 81 feedback items with a 96.6% rating and has been a member since September of 2010 (I am at 440 with 100%, a member since 1999). There are a number of things you can do to protect yourself while still using the system effectively. First, be leery of new sellers. That doesn't mean never use them but certainly be careful. Second, read auction completely. Check for condition of items, size, etc. 2 big things to verify are payment methods and shipping. Sometimes you'll see a price really low but then find they are asking for $50 for shipping. Also, verify they accept Paypal. If you pay that way, you will have some protection if you don't receive the item. Third, correspond only through Ebay's messaging system. That way if there is a dispute, the Ebay folks can easily review the correspondence. In my case here they could see that I made every attempt to work with the seller in a straight forward and diplomatic manner and that helped my case. And lastly, go through Ebay to see the listing and pay the item. I made that mistake here and clicked on the link through the Ebay invoice the seller first sent me because it "looked legit". Luckily I saw the sales tax error and didn't do anymore than that. I shudder to think what would have happened if I had attempted to log into Paypal from that fake page. Keep in mind that I work in software for a security company. I checked URL's and look for the lock icons and the like (those verify you are in secure mode). This was a really good fake in a situation where you wouldn't expect one. The only way to completely protect yourself is to go through Ebay's system for things which includes Paypal.