Sometimes it is necessary for the UN, or whoever is the global nanny, to step into a country with force to end government-led atrocities. Here's a sketch of one way to do it, and when I see it as being appropriate. First, how to do it, then when to do it is based on the cost of how to do it.
This is a tremendous disruption to the citizens even if it goes smoothly. It causes people to move, breaking social ties and business connections. And there can be a lot of death and destruction removing the current government. Often the displaced population will remember the previous arrangement centuries, and agitate for restoring it. So, this is not justified unless the cost is expected to be less than the benefit. The country has to be actively killing people and destoying/confiscating propery at a greater rate than this cure would cause, and they would have to have been doing it for years, because the cure usually takes a long time too.
For example, let's apply this to North Korea. This procedure would take out Kim Jong-un, maybe by defeating the military. It would have North Korea split between South Korea, China, and staying as North Korea but with a new leader, based on the votes of the citizens of North Korea. And it is currently not justified. As far as I know North Korea is not actively killing its citizens and confiscating their property or harming anyone outside of North Korea. It would be justified if North Korea starts dropping nukes on populated places.
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