If you want to get round export controls, just sell the product to a front company in Dubai. The middlemen will take it from there. On paper the shipment was harmless enough. Sixty-six American-made spark gaps--high-speed electrical switches used in medical devices to break up kidney stones--traveled from the manufacturer in Salem, Massachusetts late last summer to a buyer in Secaucus, New Jersey. From there, according to the export declaration, they were to be shipped to their ultimate destination in Cape Town, South Africa. But these spark gaps can also be used to detonate nuclear bombs--and it turned out that...