Chemical weapons are banned under customary international law, the 1925 Geneva Protocol and the 1997 Chemical Weapons Convention (CWC). The CWC today has achieved near universal adherence; a small number of states, however, remain outside its realm. Syria-until 2013 one of them-was long presumed to possess chemical weapons and in 2012 effectively admitted so. The Syrian civil war always carried the risk that one side or another would use these weapons. Reports to this end began to appear in 2012. In March 2013, following separate requests by Syria and several Western States, the UN Secretary-General began to investigate these allegations. Whilst the investigation team was in Damascus, a large-scale sarin attack was launched on Ghouta, killing hundreds of people. This incident and its subsequent confirmation by the UN team set in motion a series of unprecedented events leading to the elimination of Syria's chemical weapons stockpile under strict international control, supported by financial and in-kind assistance by more than 20 countries. But this multilateral effort did not end the use of toxic chemicals in Syria, and OPCW fact-finding missions have since confirmed several cases of chlorine attacks. Also, ISIS/Daesh reportedly has used chemical weapons including chlorine and mustard gas in Syria and Iraq. The paper concludes that it will be important to identify the perpetrators of these attacks and bring them to justice in order to protect the international norm against poison gas.