The unregulated international trade in conventional arms, especially in small arms and light weapons, has come to be viewed as an exacerbating factor in armed conflict, violent crime and internal repression. Concern about the negative humanitarian, development and security impact of this trade has been growing over the last decade. Against this backdrop, the UN General Assembly invited states in December 2006 to consider the feasibility of an instrument establishing common international standards for conventional arms transfers-also known as the ‘Arms Trade Treaty' (ATT). The legality of arms transfers has traditionally been treated as a question of arms control law, but in the recent debate about legal restrictions on states' liberty to transfer arms, norms of international humanitarian and human rights law have frequently been invoked. This article surveys the existing international legal regulation of state-authorised conventional arms transfers, examines how humanitarian law, and in particular states' duty to ensure respect for humanitarian law, affects the legality of these transfers and shows why human rights law does not make a significant contribution to the legal regulation of the international arms trade today.