Indeed, if you want to think really long term, you could imagine this norm further evolving into a principle of international law that is truly enforceable. But of course, this train of thought could lead to discussion of an international criminal court, and even after yesterday this administration probably isn't prepared to countenance such a thing. For now I'll settle for a simpler goal: Don't do anything rash, and don't do anything unilateral unless our friends desert us.
Any military action—including the one I've described—will have a big downside: fomenting Islamic radicalism, a radicalism that, at the grass-roots level, is simply not susceptible to normal deterrence. The object of the game is to outweigh that downside with an upside: 1) Deter the future financing of these radicals; 2) deter the future hosting of these radicals by state governments; 3) give the mechanism of deterrence the broadest possible base of geopolitical support, and hence the most enduring effect.