Denial that it has occurred won't be accepted by international community.
Evidence of culpability is not something the agents of such weapons will give out.
No one has brought forward convincing proof who the new enemy is! The new enemy knows how to use chemical weapons and then escape. Who would do that? How would they do it? Why would they do,it?
Use of chemical weapons is likely to be work of special teams who have knowledge of what to do, when to do it, and how to pull out without being caught hiding their tracks as they go about their nasty business. They have the ability to be unseen by regular troops. Such covert teams one has to suppose are trained by military staff already experienced in chemical warfare. Where do such people come from?