A UN army is not forthcoming in Somalia either...

In his Financial Times column today, Gideon Rachman makes the argument for a "United Nations army." His test case, interestingly, is Somalia, where offshore piracy has galvanized international cooperation, but 18 years of onshore violence and instability has rumbled on unchecked. Would it be easier, or any more advisable, to send UN peackeepers to Somalia if there were, as Rachman proposes, "a proper UN force on permanent stand-by?"
Maybe, but many of the same problems with deploying UN personnel in Somalia would still apply: militants would be all too eager to turn their violence onto UN blue helmets, the presence of foreigners could inspire radical nationalist sentiment, and the ensuing deaths and difficulty would only make countries more skeptical of contributing their troops to UN peacekeeping.
And herein lies a problem that Rachman does not consider. In his view, the chief obstacle to creating a "UN army" is a general wariness, primarily on the part of conservatives, to cede such power to an internationalist institution. He cites the proverbial UN "black helicopters" synonymous with world government and counters conservative skepticism by quoting the Gipper himself:
Even perfectly sane American conservatives regard the idea of a permanent UN force with horror. They might be surprised and enlightened to learn that the hero of the conservative movement, Ronald Reagan, once spoke approvingly of the idea of “a standing UN force – an army of conscience – that is fully equipped and prepared to carve out human sanctuaries through force”. And, of course, to take on the Martians, whenever they finally invade.
But a problem possibly even greater to overcome than (conservative) discomfort with the idea is the reluctance of UN member states to contribute troops. The mission in Darfur has been short on personnel for over a year and a half, and its counterpart in DR Congo can't even muster a requested addition of 3,000 troops. However one conceives of this "UN army," the soldiers would have to come from somewhere, and countries that don't contribute troops now (ahem, the United States) wouldn't be likely to sign on to a permanent deal.
Rachman's Martian example -- that fighting an alien invasion is a perfect example of when a global UN force would be appreciated -- is also revealing. For as I've argued before, UN peacekeepers are not invasion-repellers. They are peacekeepers. So I'd hope that the powers that be on Earth would be smart enough to only deploy them after a peace has been reached with these hypothetical invading Martians