An article today that is more interesting than the title might indicate. It compares two theories of how global peace can (and should) come about.
First, the "world federalism" or "cosmopolitan constitution" theory, which envisions supra-national organizations (like the United Nations or European Union) becoming larger and stronger to the point where there exists, essentially, a unified global state with an overarching government capable of exercising supreme sovereignty. In such a state, war could only exist in the form of civil war between member nations, and the supreme sovereignty would presumably be powerful enough to quickly squelch any outbreaks of such conflicts through force or economic coercion. Under this theory, people would eventually become "citizens of the world" instead of (or in addition) to merely citizens of whatever nation-state they happen to be born within.
Second, the "democratic peace" thesis. This thesis has a strong empirical foundation based on the fact that extensive research has shown that democratic countries have never warred with each other. However, democratic countries do have a statistical propensity to launch wars with non-democratic countries. Thus, if democracy is spread to more and more countries around the world, the likelihood of those countries warring with each other would drop accordingly. Various explanations are summarized in the article for why democratic countries, so far at least, refuse to engage in war with other democratic countries.
The article strongly favors the second approach, and argues that the United States should aggressively promote democracy overseas to help guarantee its national security. Delahunty and Yoo reject the "world federalism" approach both out of concerns for nation-state sovereignty and an argument that the United Nations will never become a global guardian of democracy and human rights, since it allows non-democratic member states to influence policy (even on the Security Council). Other supra-national organizations, such as the International Court of Justice and the European Union, however, are not analyzed, nor do the authors address the fact that recent U.S. attempts at spreading democracy overseas (Afghanistan, Iraq) have certainly not been unqualified successes. John Yoo, of course, is the infamous supporter of torture during the Bush administration, and from this article and other sources, seems rather skeptical of international organizations.
As I mentioned, the article addresses an interesting issue. However, I'm not sure at this early stage if policy-makers necessarily have to choose between the "world federalism" and the "democratic peace" theses. Nation-states can continue to support and strengthen international organizations while simultaneously spreading democracy through diplomatic, economic, and (occasionally) military means.