Turkish and US dealers named as sellers of "Illicit Antiquities"

Over on Christopher Jones' Gates of Nineveh blog under an important post about the weaponisation of cultural heritage by the Syrian regime, dugup antiquities trade lobbyist Peter Tompa employs the usual trade fixation with "the numbers game" to draw attention away from the potential involvement of a no-questions-asked approach to commerce in dugup antiquities and illicit artefacts from the MENA region. I suggest that we should also be looking at another area of Churkin's letter, published as an official document of the UN which is the specific naming of certain outlets which the writer alleges are involved in the trade of illicit artefacts with documentation which is forged.
 These not only include US-based eBay, but also:

vauctions.com, ancients.info, vcoins.com, trocadero.com and auctionata.com. 

Sites some of which have connections with the Ancient Coin Collectors Guild. How do these dealers verify that the documentation legitimising the items they sell is not forged?