So who died and made the UN King?

Here's something I just don't understand:  The United States along with much of the rest of the world is all up in arms because Iran and North Korea* are developing nuclear weapons.  I certainly understand why we don't want them to have nuclear tipped spears....the leadership of both countries are f__king nut cases.  OK, that might be unfair.  They might be totally rational and just have sinister regional ambitions.  I dunno.

Here's where I get lost....the world is hammering them because they have ignored a UN mandate that they cease pursuing their nuclear ambitions.  Since when does the UN have the right to unilaterally tell a sovereign nation what they can and cannot do?  

If the UN votes to tell the United States they must stop pursing the production of oil and natural gas via hydraulic fracturing, for example, because the rapid increase in worldwide oil/gas supply this would cause would upset the decades-old energy-producing status quo, would we be obligated to just say, "OK, whatever you say UN.  We'll stop.  You da boss,"?

If we didn't would the world be justified in saying they would boycott everything American, and if any country didn't support their boycott they would be in some way punished, too?  

I understand this particular scenario can't happen as long as the US has a UN Security Council veto, but still it bothers me that this international body with a....let's face it....rather lackluster record can just dictate what they will and won't allow.  Who died and made them King?  Any time they actually do anything it's the US that does 90% of it.  They write checks, then expects the US to cash them.

I would much prefer to see a multinational network of economic inter-dependency as the "carrot" one country or group of countries could use to get an errant state back in line vs a unilateral edict from the UN.  "Sugar catches more flies than vinegar."

Don't you think military conflict between the US and China is greatly reduced now that we do so much business with each other?  Why would you want to blow up your biggest customer?

Counterpoint anyone?

S

*N. Korea just today had another successful underground nuclear test.