Well, sure, it's never been a question NK would be flattened if they actually did anything. It's just a question of how many (hundreds of) thousands precede them, because day after probably isn't quick enough.
And eh smj, if you're talking technical legalities, as near as I can recall internal conflicts have been largely exempt from anything chemical weapon wise basically forever. It's possible assad hasn't actually been really violating the geneva protocol in a technical sense, ferex, and then you get into the mentioned riot suppression stuff. There'd be a pretty definite CWC violation but there's apparently a non-negligible chance they're otherwise largely legally okay to gas their own populations, as fucked up as that sounds.
... though yeah, I'm like 60% sure it being a civil war would have some pretty substantial issues so far as intervention goes, insofar as the legal side of it. Like it or not, you'd still be dealing with a sovereign nation under most circumstances, and oddly enough a lot of people don't much like nation states attacking other ones and interfering in that sort of thing (and hell, I can see why: If you want a recent example, just look at ukraine, because that's exactly why a country would be sketchy as fuck about legitimizing interfering on any side of a civil conflict except the recognised government). UN intervention and coalition stuff mitigates a lot of that, as does being called in by the originally recognized government, but the US just kinda' blatantly rolling in and rolling over assad probably does have some pretty significant issues vis a vis international law et al. Mind you, we've probably done it before and will probably do it again, but it looks like there's got to be more gaf than we seem to have for syria before we dick whip international law in that particular manner.
Russia, meanwhile, would be getting a pass because they are backing the original (and so far as I can recall still recognized) government. Makes shit complicated, particularly when we've never really cared enough (and, let's be honest about our government, still don't) to push international relations towards being actively against the assad regime.