I should say that I agree with the spirit of Reihan Salam’s argument that the egregious problems we’ve had with private military contractors in Iraq should serve, as such, to discredit the PMC problem. That the PMCs working in Iraq operate in a legal black hole is, in my mind, a huge problem but also an eminently solvable one.
That said, I’m not actually seeing the specific compelling argument in favor of such widespread use of PMCs. The arguments Reihan adduces sound to me like good arguments in favor of a professional military staffed by volunteers which, of course, is what we have.
I do, however, sometimes feel like there may be a decent case for something like the UN hiring PMCs do conduct certain kinds of humanitarian options. It’s pretty obvious why a standing UN military force might be a useful thing to have (could deploy quickly into a crisis as soon as the Security Council authorized it, etc.) and also pretty clear why you’re not likely to see one created. One could, however, much more easily imagine the Security Council creating a standing budget that could be used to fly a crack team of PMCs in somewhere to guard a refugee camp or impose a no-fly zone. Other times, this seems like a terrible idea: does Africa really need more mercenaries?