Is the recognition of a non-state armed group as the government of another state a violation of international law? On the face of it, the international law is quite straightforward on this issue. The principles of state sovereignty and non-intervention require states to refrain from interfering in the internal matters of other states, including their political independence. But, as is so often the case, things are less clear at the periphery, or where there is tension or conflict with other principles of international law. Indeed, state practice in this context tells a rather different story to the established law. This paper seeks to determine the circumstances in which the recognition of a non-state armed group during an ongoing civil war is lawful, as opposed to a violation of the principle of non-intervention and prohibition of the threat of force. This will be done through analysis of the legal limits on recognition of governments, in terms of both the criteria for recognition and the interaction between norms of recognition and other principles of international law. Recent state practice regarding the recognition of opposition groups in Libya and Syria will be assessed against prevailing international legal standards, and where practice diverges from established law this paper will consider whether the state practice is extra-legal or reflective of evolving law.