Suzanne Nossell reminds us what the United Nations is good for. The best way to sum up her list might be to say that international organizations are extremely useful for solving certain collective action problemslike tackling AIDS or prosecuting war criminals or handling peacekeepingthat no one country can or would handle on its own.
What we've seen over the past few years, however, is that the Iraq War has transformed the debate over the UN into a debate about whether or not the body should be some sort of enforcer of international law. That's surely the wrong way to look at it; the UN can very rarely force countries to do things against their will. International law is, for the most part, only as binding as the force that backs it, period, as we've seen with regards to Sudan, Iraq, Iran and many other countries.
Indeed, because of the various competing interests in the Security Council, the United Nations, on its own, will very rarely be an adequate means of punishing "rogue" states that skirt the law. On the other hand, nor will it simply rubber-stamp ever foreign policy decision the United States decides to undertake, as many conservatives would no doubt prefer. And nor can it ever be a useful means of constraining American power, as many liberals might like. The United Nations is useful as a forum for coordinating international opinion and using it to pressure certain countries, but its utility there obviously has limits. For instance, like Gareth Evans and Ann-Marie Slaughter, I'd like to see the United Nations mandate that nations have a "duty to prevent" genocide. But after watching Western nations dig in their heels over intervention in Darfur, it would be foolish to assume that any such moral imperative would carry much weight. At any rate, if we can focus on the positive things the UN can realistically do, we'll be in a much better position to figure out how and why it needs to be reformed.