Derek Fincham has an interesting post on common misunderstandings about the UNIDROIT Convention on Stolen or Illegally Exported Cultural Objects”: Getting the UNIDROIT Convention all wrong
it was an ambitious effort aimed at harmonizing the private laws of various states so as to reduce the harmful effects that occur when laws conflict. It established common rules for the restitution and return of cultural objects between states party to the Convention. At present there are twenty-nine states party to the Convention. The UNIDROIT Convention primarily seeks to return objects to their original private owner. It attempts to fill the gaps in the UNESCO Convention by firmly placing regulatory efforts on the market end of the illicit supply chain. It recognizes the inherent difficulty in relying on developing nations to police their own borders and archaeological sites. UNIDROIT creates a uniform law which requires cultural property to be returned even if a theft cannot be firmly established. It also allows for a private right of action. Its major focus is the harmonization of private international law. It produced a number of excellent and innovative approaches to the problem. Unfortunately, a number of fatal flaws render its widespread application in most major art-market states highly improbable. Immediately after its completion, the UNIDROIT Convention was met with a great deal of criticism, especially among art and antiquities dealers.Unlike the highly selective manner in which some states, most notoriously the United States of America apply the 1970 UNESCO Convention:
The biggest provision preventing states from signing on to the Convention is, Article 18 provides, “No reservations are permitted except those expressly authorized in this Convention.” This means that States Party are unable to pick and choose which provisions they accept, making it an international legal instrument with real teeth...I's worth having a look at the rest of his text and following the links befoere considering why dealers of certain types of artefacts might be opposed to it.