UNESCO Convention Farrago of Nonsense

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Jason Farago  ('Turkey's restitution dispute with the Met challenges the 'universal museum'...', Guardian Sunday 7 October 201) reckons Turkey has no right to ask the Met to show the licit origins of 18 Anatolian objects  from the  Norbert Schimmel collection:

both the US and Turkey are signatories to a Unesco convention stating that if a cultural object left the country in which it was produced before the year 1970, then it's free to circulate. 

What? Which of the Convention's 26 articles actually says that? It seems to me Mr Farago ought to tell his readers, or they might get the impression that he's trying to blacken the reputation of Turkey for daring to challenge the "right" of certain nations to hold clandestinely removed objects from other countries and unilaterally declare they are not giving them back as they've thought up the idea of a "Universal museum" which should have a carte blanche to do precisely that. Was any representative of Turkey invited to sign the declaration of the value of Universal Museums? Let's have a look, who is missing from this list? Museums signed up to the declaration:

• The Art Institute of Chicago
  
• Cleveland Museum of Art
  
• J Paul Getty Museum, Los Angeles
  
• Solomon R Guggenheim Museum, New York
  
• Los Angeles County Museum of Art
• The Metropolitan Museum of Art, New York
  
• The Museum of Fine Arts, Boston
  
• The Museum of Modern Art, New York 
• Philadelphia Museum of Art
• Whitney Museum of American Art, New York
  
  and from the rest of the world:
• State Museums, Berlin
• Bavarian State Museum, Munich (Alte Pinakothek, Neue Pinakothek)
  
• Louvre Museum, Paris
•  State Hermitage Museum, St Petersburg
•  Rijksmuseum, Amsterdam
•  Opificio delle Pietre Dure, Florence
•  Thyssen-Bornemisza Museum, Madrid
•  Prado Museum, Madrid

For the information of such of Mr Farago's readers who may be inclined to believe him, let me quote Article 15 of the Convention:

"Nothing in this Convention shall prevent States Parties thereto from concluding special agreements among themselves or from continuing to implement agreements already concluded regarding the restitution of cultural property removed, whatever the reason, from its territory of origin, before the entry into force of this Convention for the States concerned".