The use of chemical agents as a weapon of war has a history that extends back over two centuries. The first instance of a large-scale deployment of chlorine gas, for instance, occurred in April 1915 when German troops attacked Ypres (France Diplomacy, 2022). Moreover, the two world wars saw the greatest proliferation of chemical weapons on the battlefields of Europe, in Nazi concentration camps or in Asia (Office for Disarmament Affairs, 2023).

Despite the current regulatory framework, specifically the Chemical Weapons Convention, which prohibits the use of chemical weapons as well as their production and acquisition, these continue to be used today and not solely by states but also by non-state actors, as evidenced by the 1995 sarin terrorist attack on the Tokyo Underground (France Diplomacy, 2022). The evolution in the nature of armed conflicts, and in particular the emergence of asymmetrical conflicts, has led to a resurgence in the use of chemical weapons (Lion, 2009) and recent reports indicate that the threat of their use has intensified, particularly in the context of the ongoing armed conflicts (France Diplomacy, 2022; Amnesty International, 2023; HRW, 2023).

This paper examines the prohibition of the use of chemical weapons and the most recent instances of chemical weapon use. Firstly, the 1993 Chemical Weapons Convention (CWC) and the EU’s support to the Organisation for the Prohibition of Chemical Weapons is examined. After, the articles of the 1998 Rome Statute of the International Criminal Court, which explicitly identify the use of poison, poisoned weapons, prohibited gases, liquids, materials, or devices as war crimes are analysed, as well as the mens rea element required to prosecute the perpetrators of said crimes. Finally, the paper will evaluate several instances of the international community’s response to the use of chemical weapons in armed conflicts, with a consequent violation of the CWC, such as in Iraq, Syria and Ukraine.