Should auction houses adopt 1970 when dealing with archaeological material?

The 1970 UNESCO Convention on the Means of Prohibiting and Preventing the Illicit Import, Export and Transfer of Ownership of Cultural Property provides a convenient benchmark when discussing recently surfaced archaeological material. The Association of Art Museum Directors (AAMD) has adopted this date when considering new acquisitions. The objects returned to Italy from North American museums have included objects that were acquired during the 1970s.

Lord Renfrew of Kaimsthorn, speaking in the House of Lords last week, drew attention to the October 2008 sale of archaeological material at Bonham's in London when several lots had to be withdrawn. These controversial lots all surfaced after 1970.

There is now news that two further pieces, an Apulian situla and an Attic pelike, have been seized in New York. It seems that they passed through an auction in New York City in June this year. Both appear to have surfaced through a Beverly Hills Gallery.

On 1 June this year a Corinthian column-krater was seized at Christie's. It apparently surfaced at a London auction. Items that featured in the same London auction back in the 1980s have also been returned to Italy.

Would auction-houses and dealers be wise to adopt the 1970 date for handling archaeological material?