Which particular chemical weapons are we discussing?
Smouldering wood, used for gassing people in basements?
Chlorine - used in bulk for water treatment across the middle east?
Or nerve-agents, such as those used at Ghouta? Which were created by local fanatics using precursors smuggled in from Turkey.
I'm not seeing why the existence of these weapons would necessarily implicate the Russians.
During Obama’s reign, the Russians promised (evidently as part of out hands off the Ruskies with greater flexibility policy) to insure Syria destroyed all her chemical weapons - a year ago, sarin was used and now it seems as if chlorine gas was used...both Assad and Putin agreed to the deal.