Overaggressive US Prosecutors Basing Sotheby's Seizure on Repealed Foreign Law?

It appears that the US Government is hinging its seizure of a valuable statue from Sotheby’s based upon French colonial era laws that were repealed when the Khmer Rouge took power. See http://www.nytimes.com/2012/02/29/arts/design/sothebys-caught-in-dispute-over-prized-cambodian-statue.html?ref=design

However, even assuming such colonial era laws vested absolute title over the statue in question in the Cambodian state, there is a real question whether they remain in force today. This is what a UN Report has to say on the subject.

According to Article 158 of the 1993 Constitution, laws and regulations which safeguard state property, as well as the rights and property of private individuals, and are consistent with the national interest, continue to be in force unless and until they are amended or repealed, except to the extent that they are contrary to the spirit of the Constitution. There have been sharp disagreements in the interpretation of this Article, between those who would prefer to limit its effect to those laws and regulations which were actually in force immediately before the entry into force of the 1993 Constitution, and those who seek to use its provisions to revive laws which had been in force prior to the Khmer Rouge regime, but have in effect been repealed by the Khmer Rouge. It is an issue which would need to be addressed and successfully resolved, through passage of fresh legislation, if need be, if the objectives of the publication of laws are to be fully achieved.

See http://unpan1.un.org/intradoc/groups/public/documents/APCITY/UNPAN004695.pdf

This issue obviously requires additional research, but it again raises the legitimate question whether collectors, museums, dealers and auction houses should be subject to civil and/or criminal liability based on the vagaries of foreign law.