Traditional retailers of used goods like pawn shops are usually subject to pretty stringent regulation - not necessarily to determine if goods are stolen, but to record identification of the seller to enable an investigation later. In some places this does include proactively sending a report of items to the police for checking against stolen reports. So there's a pretty clear precedent for regulation of this kind directed towards online marketplaces, but you can no doubt predict the questions around the difference between a pawn shop (being the seller) and Facebook (being not the seller but just a provider of listings).

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