Former Obama National Security Adviser Susan Rice and others who say the U.S. can live with a nuclear-armed North Korea cite deterrence and the North’s certain destruction if it attacks Americans. This is a convenient faith, but alas it ignores the threat of proliferation to other regimes or actors that might also use weapons of mass destruction against Americans.

This proliferation threat was in sharp relief Tuesday with leaks from a confidential United Nations report alleging that Pyongyang is circumventing trade and financial sanctions and plying its military wares and knowhow to dozens of nasty foreign customers, including Bashar Assad’s Syria.

The Journal’s Ian Talley reports that the North has shipped 50 tons of supplies to Syria, including “high-heat, acid-resistant tiles, stainless-steel pipes and valves,” likely for use in a chemical weapons plant. The report, written by the Panel of Experts that oversees North Korea’s compliance with U.N. resolutions, reveals more than 40 shipments between 2012 and 2017. It also claims Pyongyang sent weapons experts to Syria multiple times as recently as the past two years.

This would solve the mystery of how Assad obtained the sarin gas he used against his people in 2013 and again in 2017. The U.S. believes he is still using chlorine gas against civilians. In 2007 North Korea worked with Syria to build a nuclear-weapons facility at Al Kibar—until Israel destroyed it in a military raid, against the advice of George W. Bush and Condoleezza Rice.

The chemical-weapons news also underscores the porousness of U.N. sanctions as the North sells whatever it can for cash to keep its dictatorship afloat. If sanctions are going to stop North Korea, the U.S. and its allies will have to start boarding ships and commandeering aircraft believed to be carrying WMD material. North Korea will sell anything to any bad actor for a price.