Frederick Warmbier went to a country that you are advised not to visit. (bad idea) Furthermore, it happened to be a country that we recently bitch slapped with sanctions. (another reason it was a bad idea) Then, he got caught trying to steal a political banner from the hotel he stayed at. Congratulations, your officially an idiot. You just had to have that souvenir didn’t you! (source)
It doesn’t matter if 15 years is a bit steep. When you are in another country, you need to play by their rules. No matter how stupid they are. If for whatever dumbass reason you feel compelled to venture into North Korea, you should know they pretty much make them up as they go along. So sit quietly in your hotel room and hope for the best.