North Koreans not smuggling WMDs, says British expert

Hazel Smith, a British expert on North Korea, said in a report that North Korea's 242-vessel merchant shipping fleet is too old and faces too much scrutiny in foreign ports for it to be a significant conduit for weapons of mass destruction. 

Even "allies" like China, Russia, and Vietnam impose strict inspections of North Korean merchant ships, "which are frequently stopped and even detained for serious safety violations."

That doesn't mean Pyongyang doesn't transport WMDs to other countries; they do use their own aircraft or the vessels of allies for that purpose.