I asked this question before and didn't get much in the way of a response: If you buy a forgery from them, sue them and bring experts to court who agree it's a forgery, and the court agrees you've been sold a forgery - can you not then require them to divulge the consignor? And if you did this a few times, and the consignors were always the same group of guys, and there was no realistic, proveable provenance for the items, couldn't that lead to a bigger action of some sort?