Yes / Article IV of the Biological and Toxin Weapons Convention sets out the obligation for States Parties to implement the BTWC through appropriate national measures. Although some States have enacted such legislation, others have not and the Aum Shinrikyo incident in Tokyo in March 1995 underlined the importance of appropriate penal legislation both to implement the BTWC (and the Chemical Weapons Convention) and to criminalise any development, production, stockpiling or acquisition of such weapons for terrorist or criminal purposes. This Briefing Paper reviews the development of the language relating to Article IV of the BTWC by the four Review Conferences, notes the requirements of the Chemical Weapons Convention and then addresses the opportunity provided by the Ad Hoc Group negotiations to strengthen the BTWC through stronger implementation measures.