The Independent explains the bind the auction houses are in with the Medici Dossier, a file of 20,000 photographs held by the Italian police identifying works sold by Giacomo Medici who dealt in looted antiquities. The auction houses and the Art Loss Registry have no access to the dossier which complicates the work of identifying looted works that find their way to auction:

Selling goods once owned by a notorious art thief would undoubtedly sour the reputation of Bonhams, one of the most reputable auction houses in the world. But Bonhams was aware of the potential criminal link between lots 94 and 95. Days before the auction the house received an email from an eminent academic alerting them to the questionable provenance of the lots, but it pressed ahead with the sale.

The Italian authorities refuse to share the Medici Dossier with auction houses or the Art Loss Register, the international body which authenticates ownership of works of art. This makes it difficult to remove items for sale even if they are cited as being pictured in the dossier, potentially leaving British auction houses open to the accusation that they are dealing in stolen goods.

“The onus is on Bonhams or any auction house to do a due diligence test and make sure that they are not selling anything that could have come to them via illicit activity,” said Dr David Gill, a reader in Mediterranean archaeology at Swansea University and the person who suggested to Bonhams that lots 94 and 95 in this month’s sale were from the dossier.

In their defence, auction houses say that they cannot be expected to withdraw an item which has been authenticated by the Art Loss Register – to do so would be breaking a contract with the seller – on the say-so of someone who has seen parts of a dossier to which the auction houses have no access.

Bonhams: Lots of Trouble on New Bond Street (Independent)