North Korea is seen as an oppressive regime, but they have one specific freedom that Americans don't. They can smoke weed whenever they want without a care in the world. In fact, the government actually promotes the use of marijuana over tobacco as a healthier alternative. It is also cheaper than smoking tobacco.
Weed grows freely on the side of the road and on farms in North Korea. They also promote the use of opium. Their weed is of a much weaker strain than the strong stuff in the U.S. And other parts of the world. Plus, they don't advertise or tell foreigners where to find weed, because they don't want to become the next Amsterdam.
They've never had laws against the use of plants they see as harmless, and marijuana and opium are seen as just that. It is is very socially and legally acceptable in the society to toke up whenever. In fact, they're known to pick a plant on the way home from work and smoke it to unwind as they stroll home.