Against the backdrop of the resurgence in the use of chemical weapons – particularly nerve, blister and lung agents – in recent years, as observed in the armed conflict in the Syrian Arab Republic, and the increasing volatility of international agreements, as demonstrated by the announcement of several African States to withdraw from the ICC Statute in 2016, a thorough analysis to determine the current state of customary international law with regard to the use of chemical weapons in non-international armed conflicts is in order. The paper first contextualizes the issue in relation to recent events involving chemical weapons before giving an overview of the ICRC Customary International Law Study’s approach taken toward these means of warfare. Thereafter, a short chapter sets the tone for the analysis by giving an account of the theory of customary international law. The actual analysis of the state of customary international law comprises an examination of incidents of confirmed use of chemical weapons in non-international armed conflicts. In addition, relevant resolutions of the UN General Assembly and Security Council are thoroughly scrutinized. Finally, relevant multilateral treaties are examined closely before final conclusions on the issue in question are drawn.