The chapter looks at when arms transfers to armed groups will be illegal under international law, when the use of certain arms by armed groups will be illegal and what are the factors which allow us to consider armed groups bound by these prohibitions at the international level. The situation in Syria is highlighted and there are references to the ongoing negotiations at the United Nations for an Arms Trade Treaty. Particular attention is paid to the issue of the obligations of armed groups under human rights law and recent developments which suggest that such groups are bound by international law even where, as in the early stages of the Syria fighting, the militia or armed group are not necessarily in control of territory or in a situation of armed conflict.