"Rules only stay rules if they are enforced."

Bookworm links to an article in The Week by Pascal-Emmanuel Gobry.

Whether you like it or not, America is the world's lone superpower, and its military dominance over the rest of the world has, despite all its flaws, produced an era of unprecedented peace and prosperity. The phrase "world policeman" is usually taken as a pejorative, but it is actually extremely apt: A policeman should not be a nanny or a busybody, but, by god, if he sees a thug punching a grandmother, he should intervene. It is actually the antithesis of that other pejorative word, "empire." In political theory terms, a policeman enforces a minimal rule set — what you must not do — whereas an empire enforces a maximal rule set — what you must do. A world empire would be a disaster, but a world policeman is a wonderful thing. And since there are no other credible candidates, America — meaning President Trump — must be it.

Now, one of the rules that America has decided to enforce — and it is a very good rule — is that if you are a state and use weapons of mass destruction, you will be punished. The problem is that rules only stay rules if they are enforced.

The purpose of the Syria strike was not to effect regime change in Syria, or even to alter the balance of power on the ground, it was to enforce the rule after it was flouted by Syria, with the almost certain aid of Russia and, probably, Iran. In this case, the Trump administration was simply doing its job as a policeman. The fact that Barack Obama had previously refused to endorse the rule, thereby imperiling it, made this action all the more necessary and laudable.

Read more here.