On 4th March 2018, a "nerve agent" - referred to as "Novichok" (newcomer) - was used in Salisbury, England - CBS News 13th March 2018. The UK Prime Minister - Mrs Theresa May - stated that it was "highly likely" that Russia was responsible for this - see her Statement of Monday 12th March to Parliament.
In this post of 23rd August 2013, chemical weaponry was discussed in connection with the conflict in Syria.
The Chemical Weapons Convention lies at the heart of the position in international law regarding chemical weaponry.