Lots of conversation above about did he, or didnt he and if it could be proven.
Either way Northwest is going to pay big time "Go Away" money to avoid a civil Lawsuit.
The fact that the yo yo Stew had previously been nabbed for bringing in Chemicals is not going to sit well in court. I think his only saving grace may be that the stuff he used could have been over the counter medication in Europe, wheras it requires a prescription in the U.S. ,and it was done in International Airspace.
Either way bad judgement enough that he will be a passenger next time he steps on a plane.