Two decades ago, the notion of arming an uninhabited aerial vehicle (UAV) was little more than a niche pursuit. Today, at least 20 countries have weaponised UAV systems in their inventories, with other nations pursuing acquisition, while the capability is also proliferating to non-state actors. The air vehicles range from small, crude, hobbyist-style UAVs favoured by some non-state groups, to large, long-endurance platforms capable of being fitted with a range of sensors and air-to-surface weapons. Technological development continues apace with an increasing emphasis on greater automation and reducing the human workload, along with the emergence of a type of hybrid UAV and air-to-surface munition along side the more established loitering munition. While uninhabited systems are increasingly embraced by many armed forces, they remain an uneasy subject in the wider public realm, where the perceived lack of human control remains an ethical issue. There also continues to be concern in the legal community regarding how increasingly automated – and perhaps one day autonomous – weapon systems fit within the law of armed conflict – legal concept rather than legislation, sometimes also referred to as international humanitarian law. These subjects were the focus of a 21–22 June 2021 seminar organised by IISS Europe to help further the debate and to better understand the implications of weapons-capable uninhabited systems. This paper reflects the discussions and many of the issues raised by the participants.