Actually, they did.....when they passed Resolution 1441 (stating that there would be severe consequences if Saddam didn't immediately join the human race) the USA proudly and forcefully enforced their resolution.
Strange, the UN didn't seem terribly happy about it.
Perhaps it was because they knew that it meant that their fraudulent oil-for-food gravy train would be run off the tracks pretty soon.....
If true they need to be sent a bill for services rendered. Oh wait....The US pays most UN costs ... never mind.
Their happiness is dwindling more so lately, even with the support of France, Germany, and Russia (which IMHO will dissolve soon) for the workings are in place to blast the worldly deceit funneled through the UN wide open.