In Iraq and the Police Principle, Nathan Smith examines the “world policeman” analogy:
While the notion of America as ‘world policeman’ is often mocked, to understand the principles by which a police force maintains order in a city is essential to good foreign policy.A police force must (1) be (and be known to be) stronger than anyone else in the city, and (2) operate according to the law, i.e. by a set of well-defined and public rules and procedures. If these conditions hold, citizens live under a generalized credible threat that illegal behavior will be punished. Prosecuting a crime is costly — to the taxpayer who pays cops’, judges’ and wardens’ salaries, to the criminal who loses his freedom or his life, and to the occasional innocent who is convicted by mistake — and does not right the wrong — murder victims cannot be revived, rape cannot be reversed. But the prosecution signals to other potential criminals that obeying the law is in their interest, and society benefits from the crimes that are not committed (or even contemplated) for fear of the police. In the same way, a judicious use of military force can establish a generalized credible threat against potential aggressors or murderous tyrants, thus amplifying the returns, in peace and freedom, to the occasional intervention.
The first Gulf War is a shining example of foreign policy that exploits the police principle. In expelling Saddam’s forces from Kuwait, we applied overwhelming force against one aggressor, and in the process established a generalized credible threat that overwhelming force would be, or at least was likely to be, used against aggressors elsewhere.
The threat was credible not only because we won the war handily — everyone (but Saddam) knew we would do that, once we started — but because air power enabled us to do it with few casualties, which made it more likely that we would be willing to do it again.
The threat was generalized because our intervention had the firm backing of international law. International law is conceptually problematic and morally inadequate: it habitually legitimizes dictators while often denying democracies the means to defend themselves. (The Israelis ignore it to survive.) But it is an efficient tool for defining thresholds of acceptable behavior.