Geektastic: The UN should be running the world on the basis that there are Rules. If you break the rules and won't cease after reasonable requests, you should be 'cut off' for the good of the remainder.
But the UN doesn't run the world and UN member nations can't and shouldn't have their sovereignty overruled. They can deplore the actions of a member nation but can't compel then to comply with demands. If a sovereign nation asks for our help we should consider it, but if they don't, we really have no right to be there and showing up is an invasion, which is certainly how many in those nations see it.