The ideal solution for any peacekeeping force or "world policeman" would be to have a combination of people from many nations under the rule of specific and objective laws.

In theory, the U.N. is supposed to fulfill this role, but has largely decayed into a greedy and corrupt organization that treats free nations and totalitarian hellholes as though they were no different. The ideal of bringing "law to the Old West" doesn't work if you make Jesse James the sheriff. The failure and corruption of the U.N. is why the United States had to organize its own coalition to go into Iraq.

Either the U.N. has to be reformed somehow, or a new world organization, with extremely limited and objective roles in protecting rights around the world (defense and such), has to be created. If the new organization decides it wants to be a world government in the worst socialist EU sense, or yet another vehicle for looting the prosperous nations for the benefit of the totalitarian ones, the solution will be worse than the problem.