"brutal regime" describes tons of places however. You need to quantify what the charges are and why NK specifically would come under them, that we wouldn't also apply to other places in general. I'm sure you can, but it needs to be specific and within the ICC's legal framework.
e.g. 120,000 people in North Korean labor camps seems like it must be a lot, because North Korea is small, but it's still far less than the total US prison population, on a per-capita basis. NK has about 0.5% of its citizens locked up, and USA has almost 1% of citizens locked up. So you're locking up Americans about twice as fast as NK locks up their own people.
However, if you look at just black people, they make up 34% of the US prison population and only 12.1% of the total population. They're a total of around 3 times more likely than "average" to be locked up. This makes a black American about 6 times more likely to be locked up than a North Korean. This is in possible breach of the "crimes against humanity" law of the ICC:
- "systematic attack directed against any civilian population"
including
- "Persecution against any identifiable group or collectivity on political, racial, national, ethnic, cultural, religious, gender"
- Imprisonment or other severe deprivation of physical liberty in violation of fundamental rules of international law
- Enslavement
https://www.hrw.org/world-report/2018/country-chapters/united-statesOther longstanding US laws and practices—particularly related to criminal and juvenile justice, immigration, and national security—continued to violate internationally recognized human rights.
So ... good reasons why you guys don't actually sign up to the ICC, but also good reasons why you should
harass your government to do so.