Disolve the U.N. as a law-giving body, and make it a humanitarian organization.
Also, create an institution which every country is required to attend, and make it for mediation purposes only. Kind of a round table discussion on what is going on in the world. The institution will be used for nation mediation only - it will not disburse military aid, nor humanitarian aid (that will be the U.N.'s new function) - its sole purpose will be for point of contact and mediation, making the countries themselves settle the matters, thus dropping the beauracracy. Since there are no leaders there, only mediators, every country will be treated equally - meaning the U.S. is treated as an equal to Uganda for instance, and vice versa.
Nations need to learn to work together, not against each other, and having a global body that gets in the way of that and tells each what to do, especially when they reinforce practically none of it, will only divide nations.
Thus, if 2 countries want to go to war, let em.
This may sound very cold hearted, but many people won't understand the value of peace until they have experienced war, or have someone who can relate it to them.
Essentially, you can only be successful in the long run if you do one of 2 things:
1) Become a mediating body that teaches nations to work with each other - this means if 2 nations after mediation decide to go at each other - you let them, and let them find out the hard way about how to settle their differences.
2) Create a humanitarian body with its own army, that reinforces every article it passes. If a nation has been uncooperative in a search for WMD's, then THAT power goes in, and takes no crap from anyone. It doesn't just create laws - it enforces them, and strictly.
You wanted a better solution - there is 2. Not saying they are great, but they are better than what is in place right now, and to be honest, they are the only 2 that could effectively work in the long run.
As much as people want to say "no, we can't have war, no matter what!", its a necessary evil, that only becomes unneccessary when you have everyone in the world willing to not go to war. The biggest mistake these people make is treating everyone in the world as if they have the same thought process as they do - a cultural ignorance.
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*Joren, Legend, Alleged Egomaniac, Thread-Killer, 2-time Ban Recipient, and 6th Grade Spelling Champ*
*Joren, Legend, Alleged Egomaniac, Thread-Killer, 3-time Ban Recipient, and 6th Grade Spelling Champ*