From a Guardian article: "North Korea is banned from nuclear tests .... under UN sanctions dating 2006 and most recently ..."
What is the exact relation between UN and North Korea ?
Where comes the UN jurisdiction over North Korea from ?
The jurisdiction of the UN is derived from the fact that North Korea joined the United Nations in 1991. UN resolutions are binding for all member-states. Enforcement of UN resolutions is usually not done through force but rather through sanctions. Sanctions usually mean that countries refuse to trade or cooperate in other ways with the violating country.