This is just straight up false, as usual with far-right propaganda.
The UN isn't the one preventing travel between regions of the DPRK itself, and shooting anyone who crosses the border. The resolution clearly states that people, ships or anyone cannot be sent back to the dictatorship if it causes humanitarian issues (which basically prevents anyone from being sent back, since living in North Korea is in itself a humanitarian issue). Besides, the resolution applies to North Korea nationals, but if they happen to have dual-citizenship with, say, South Korea (which is automatic), they will not be affected.
my favorite part about that is that there's literally a fucking memo from the state department in the 50s where an undersecretary is like "yeah basically we're going to starve cuba to force regime change" in, you know, not those words. Like they fucking say it.
so yeah sanctions have no effect (but the people doing the sanctions have literally said "we're going to put the screws to the people to make them so desperate, diseased, and plagued by death that they revolt")