In the context of my ongoing skepticism about the effectiveness of regulation for improving biosecurity, here is a quick note on the utility of export controls for restricting transfer of sensitive technology.
Over at Wired News, Noah Shachtman has a post pointing to an article in Mother Jones about all the US weapons that are winding up in the hands of Iran. Re-sale by third parties seems to be the short answer, but read the article to get the full story.