A report by Benjamin Sutton ("More Antiquities Woes for U.S. Museums Loom, As Turkey Demands 18 Artifacts From the Metropolitan Museum", Artinfo March 20, 2012) discusses the post on Chasing Aphrodite that suggests that the Turkish Government is requesting objects from the Norbert Schimmel Collection. It appears that the claim is covered by Turkish legislation and precedes the 1970 UNESCO Convention.
It will be interesting to see if Turkey pursues the series of bronzes that were removed from the Sebasteion at Bubon. One of the statues now resides in a private collection in New York.