If he is purchasing again with another account, and you can prove (address, name etc) report it via the automated "report a buyer" system. I would just ship and see. You will pretty much have him by the balls on any ebay claim.
Assuming you blocked the first buyer. If so...If it is the same ship to address, he is in violation of eBay policy concerning circumvention of block list. Report them and then just wait and see what he does.