Not sure, actually. I tried to search it up but it was very vague as to whether or not individual ownership and mining of bitcoin is disallowed in North Korea. I would assume that you are risking to persecution as the government does not want any sort of way for the citizens to be able to communicate and trade with the outside world.

Even if it is legal i doubt that many north koreans know about bitcoin at all. Internet coverage is probably less than 1% in that country as well, and they have their own OS that probably isn't compatible with any bitcoin software.

A guy did risk it by going into north korea and sending a bitcoin transaction, though. This just proves that btc can be used anywhere, even in totalitarian regimes. This is the definition of the ultimate hedge against fiat collapse, and government collapse.