I believe the only way to do this is to strenghthen, and grow, the cross-border alliances and Institions such as the EU, NATO, the AU, the OAS, the Commonwealth, La Francophonie, and even APEC. I believe that only through the enlargement and strengthening of current military alliances, economic fora, and political groups, will the threat of state-vs.-state war be averted in the future.First off, many of these organizations are currently working at cross-purposes when it comes to international security. Take the example of the EU vs. NATO. France and Germany, not to mention Russia, would love to see a strong EU security aparatus (to remove the American preponderance from Europe.) If the Atlantic community faces another rift similar to Iraq, I can definitely see NATO falling apart.
A lot of people see the EU as a military weakling, and in many senses this view is correct. But there are two important caveats to this: First off, the EU is already putting together a military force, which already is seeing action in Macedonia. Secondly, the EU members actually have more men under arms than the US - and most of them are members of NATO, so combining some of these forces should be less difficult than it might otherwise be. In relatively short order, the EU could put together a larger force than most individual countries. This is really a matter of paperwork more than anything else.
But what could force the EU to go this route? Well, if the US continues to be unpopular in Europe, it's imaginable (though perhaps not likely) that the US might leave or be forced out of Europe. Of course, this would only happen if the NATO member states were ready to see their security as being threatened, not guaranteed, by a continuing US presence. The EU would also need to be prepared to guarantee it's own security for the first time since 1945. Actually, I think this is one of the easier aspects of this scenario - Germany and France are both looking for ways to flex their muscle internationally, and it's no accident that they've both been the loudest voices calling for a EuroArmy. The EU army would still be a small fraction of the size of America's, but would certainly be able to play a role in regional peacekeeping.
More importantly, the EU increasingly has greater "soft power" than the US-based NATO. There are many countries that would welcome a European force, but would shun an American one, or one that was perceived as being an American facade.
I think this is a process we'll see more of in the future. In Asia, ASEAN members have already proposed adopting much of the adornments of the EU. A similar process is already underway in South America, and the AU is already slowly taking shape. Regional organization will, where possible, take over their own security in places where the US or foreign organizations have played that role.
Where I disagree with Chrisale is the possibilty of international organizations to enforce international law. Certainly, the idea of some international court of appeal is appealing on an emotional level, but I think it's impossible to imagine China or the US agreeing to that. Given the problems Ontario is having on the issues of Muslim jurisprudence, I find it hard to imagine one international court. Several regional courts is a far more likely possibility, in my mind.
The other thing I'll say is that I think none of this will happen to consciously guard international peace. Rather, we'll see a shift from national to regional security for simple national-interest reasons, not out of a "Duty to Protect." Let me say that I certainly would like to live in Chrisale's future - I just don't think we'll see it in our lifetimes.