The page linked to below has a link to download a lengthy paper about the application of the National Stolen Property Act to return cultural property to its country of origin. Reading through the document however, starts to reveal that it is aimed mainly at shoring up the position of the Ancient Coin Collectors Guild  who are eager to argue that personal ownership (by its members) should over-ride normal legalities . This has been a long running saga, with large amounts of foot stomping in the hope that they can obtain special exemptions or get the US State Department to change its mind on the application of the various laws that are upsetting the ACCG.
Quite why the ACCG should be exempted from the law is entirely unclear to me. They seem to be carrying on the tradition of collecting for personal benefit at the potential detriment to others that ought to have died out at the end of the age of imperialism.
Social Science Research Network 
Unveiling the Executive Branch’s Extralegal Cultural Property Policy
Stephen Urice, University of Miami – School of Law
Andrew Adler, University of Miami
August 13, 2010
University of Miami Legal Studies Research Paper No. 2010-20
In this Article we reveal that the executive branch of the United States has consistently – and astonishingly – exceeded constraining legal authority with respect to the movement of cultural property into the United States. To illustrate this assertion, we identify three distinct categories of extralegal cultural property practices. First, we describe how the Department of Justice, misapplying the National Stolen Property Act, has obtained the return of cultural objects to their countries of origin by filing legally-deficient civil forfeiture complaints. Second, we describe how the Justice Department has pursued this same objective by proceeding under a legally-erroneous interpretation of the Archaeological Resources Protection Act. Third, we describe how the Department of State has repeatedly undermined the statutory structure and mandatory criteria of the Convention on Cultural Property Implementation Act, resulting in significant import restrictions on cultural property. All of these practices exceed constraining legal authority and lead to a similar result. Accordingly, we describe this pattern of practices as forming an extralegal cultural property policy. We express no opinion about the wisdom of this policy. Rather, our purposes in unveiling this policy are to promote a rigorous and transparent review of the executive’s practices and to restore the rule of law. In our conclusion we speculate as to why the executive has undertaken these practices and, among other observations, suggest with some sympathy that the current legal framework is outdated.
Working Paper Series
Date posted: August 15, 2010 ; Last revised: August 16, 2010
The full article can be downloaded from the link at the top of the page linked to above (marked one click download).