A discussion about extralegal import restrictions on coins took place at the recent ACCG gathering conducted during the New York International Coin show. See http://www.numismaster.com/ta/numis/Article.jsp?ad=article&ArticleId=24783
Import restrictions under the Convention on Cultural Property Implementation Act were meant to be narrowly tailored to protect archaeological sites in specific countries. Unfortunately, due to the extralegal activities of State Department bureaucrats and their allies in the archaeological lobby, these restrictions have instead morphed into grossly over broad import bans on whole categories of ancient coins regardless of their find spots.
As such, these extralegal restrictions appear designed to suppress the trade as a whole so that cultural bureaucrats in source countries and their allies in the archaeological lobby can monopolize the study and preservation of even the most common artifacts from the past. That was not the intent of the CPIA. It was instead meant to balance all interests, including those of the trade and collectors.