I guess I was thinking about a unilateral intervention by a single country's army. UN peacekeepers are a different thing altogether, both the scope of the mission and the goals are usually very different. I don't have enough information to know how would that turn out. Keep in mind that they would be going into a very complex system that includes actors such as: the drug cartels, federal and state police, the Mexican army, federal and state political bodies, (multiple) self-defense civilian armies, (multiple) organized protest movements. The more official of those actors are - to an unknown degree - corrupted/infiltrated/colluded with the cartels. The more unstructured ones might very well consider peacekeeper intervention forcing them to disarm or stopping them from protest acts (which have included burning a state police building, an act that had surprising public support) to be further government repression.

In general I think just having independent media and investigators from outside the country can be helpful, since they can be perceived as not part of the system of internal corruption. I think it gets a lot more complicated when you have international actors as supposed to observers and/or pressure. Not saying it can't work, but it is far from simple to predict... (there are, of course, people who know great many orders of magnitude more about the issues involved than I do, both within and without Mexico, so maybe someone is looking into whether or not that sort of intervention would help).

I just visited Rwanda and Bosnia a couple months ago, and I heard stories about the UN failing miserably in both places only a couple of decades ago. A guide in Sarajevo even said the UN would sometimes accidentally return captured Bosnian civilians to the Serbian army on the hillside. With "friends" as competent as that, Mexico would probably be better off without UN soldiers.

The UN made plenty of mistakes. But that does not mean the situation with their actions is worse than what would have been without. Without such competent friends your guide in Sarajevo might not even be alive today.

Yugoslavia was an ugly war, the 'coalition' made plenty of grave mistakes but in the end it did stop a conflict that would have most likely ended much worse.

I have friends on just about all sides in that particular war and it is absolutely incredible how explosive Yugoslavia was under Tito and how vicious a conflict buried for decades flared up right after he died, it was really only a matter of time and even today I feel that it would possibly re-ignite if not for some dire threats.

Apologies, but I have to nitpick.

UN actions (ie. the arms embargo) made the conflict unbalanced - giving the advantage to one side, which then proceeded to run amok. Then, the UN repeatedly failed to protect civilian populations from this aggression. The current 'stability' in many places is an artificial equilibrium, maintained by outside forces and those 'dire threats'.

The conflict should reignite - for justice, but just as importantly, for lasting stability.