How will "civilized nations" deal with countries that use banned (nukes, chemical, bio..)?
Given the trends underway, we're likely to see less of a conventional response than in the past. Not only is a conventional response potentially catastrophic -- as we saw when the Bush administration trumped up evidence of WMDs in Iraq and invaded the country in response -- it's not that effective.
What can we expect to see? A more direct approach. The targeting of specific individuals in the hierarchy that made the decision to use the banned weapons. An extralegal process that doesn't look much like traditional warfare and much more like how nation states hunt "terrorists."
In the case of Syria, the evidence would be presented and adjudicated in an extralegal process. The portion of the national hierarchy involved in the use of the banned weapon would be deemed a terrorist organization and specific people would be placed onto a target list, prioritized, and then hunted as individuals.
I suspect, as this process matures, targets will be made public (listed on the Internet) and given 60 days to give themselves up). After that, it's a one way ticket. Drones away...crowdsourced manhunts...NSA big data...and an eventual explosive death (with the requisite collatoral damage that nobody seems to care about).
In short, warfare in the 21st century IS becoming very, very direct and very public.
The countries that continue to pay for the the big weapons and large organizations of the last century are just wasting their money.