The US Passed Laws Such as the 1983 Cultural Property Implementation

The U.S. passed laws such as the 1983 Cultural Property Implementation Act and signed treaties with several countries that specifically prohibit the importing of artifacts without established "pedigrees.' Some of these "grandfather in" artifacts excavated before the treaty's date. This means that

A) there is no longer control over the artifact trade networks and illegal transfer of artifacts across national boundaries.
B) an importer cannot be held responsible for artifacts that they did not know were illegal.
C) an importer must now prove that artifacts were excavated prior to the treaty's date or were otherwise obtained in ways not prohibited by the treaty.
D) it will become easier and easier for someone to import illegally acquired artifacts.