Nathan Elkins writes about German archaeologist Michael Muller-Karpe's refusal to hand over a gold vessel that Muller-Karpe claims to be stolen from Ur in Iraq to German customs authorities. See: http://coinarchaeology.blogspot.com/2009/07/curious-case-of-gold-vessel-from-ur.html
Muller-Karpe is certainly well-known in Germany for his anti-collector and anti-trade views. Thus, it is a bit surprising German customs ever viewed him as someone who could be trusted to provide an independent opinion on the origin of the vessel in question. Now, Muller-Karpe has evidently taken the law into his own hands because he disagrees with the efforts of German authorities to take the vessel back into custody. Presumably, he fears it will be returned to the action house from which it was seized.
US law enforcement should also be wary of similar "free help" from US archaeologists with an axe to grind against collectors. Such archaeologists have their own agendas as Muller-Karpe's recalcitrance suggests.