I don't see any requirement for any nation to remain a member of the body. Therefore, it is unable to act as a worldwide governing body.
Bolton took a stand against the gun grabbers in the UN. To me his message to the UN is to stop trying to reach into areas of national sovereignty that have nothing to do with relationships between countries, while at the same time redirecting the UN into areas that *do* affect relationships between nations. Terrorism crosses borders. If it didn't, UN the shouldn't be actively involved with it.
It doesn't matter whether they're "required" to or not. The fact is that they almost univerally (or perhaps completely universally) do remain, and that wouldn't be the case if there weren't consequences for leaving that countries aren't willing to accept. Once you have that basic element, you effectively have the beginnings of a government. Governments have a tendency to get more powerful over time, especially when few people are paying serious attention.
To me his message to the UN is to stop trying to reach into areas of national sovereignty that have nothing to do with relationships between countries, while at the same time redirecting the UN into areas that *do* affect relationships between nations.
We should know from our own constitutional history (think "commerce clause") that there's almost no problem of government that can be incontrovertibly considered a purely internal matter. It's a total fiction to say that by confining a superintending authority to "external" matters only, it won't end up swallowing all powers. Either you're a sovereign nation, or you're not a sovereign nation. That's all there is to it.