When was the picture taken? I have also seen them carrying the Daewoo version of the M4.
When I was going back to Korea about 3 years ago, they stopped me for a "sword." It was a gerber folder with a 3 inch blade. They were all concerned about it, even bringing in a supervisor, asking "why do you need it?" I explained I enjoyed camping, hiking, and fishing, and they were still very concerned. Eventually I showed my state issued firearms license, telling them I carry guns in the US, and am authorized in my state to do so. They took it well, and let me keep it, warning me to travel by train and not by air with it (there is NO security/metal detectors) in the trains or stations. Funniest thing of all was that they didn't say a thing about my Cold Steel trail hawk sitting in the bag.