The question to be addressed is whether the war crime of perfidy exists in the law of war pertaining to non-international armed conflicts. Is it appropriate to apply this term outside of international armed conflict, where the rules are defined by treaty and customary international law? The Manual on the Law of Non-International Armed Conflict suggests that at least some of the conduct defined as perfidy when occurring during an international armed conflict is also perfidious when occurring during non-international armed conflicts. What are its parameters and how many of the concepts from international armed conflict are to be incorporated into the law of non-international armed conflicts? The law that applies to the conduct of armed forces in a non-international armed conflict is derived from treaty law and customary international law. However, the customary international law status of perfidy in non-international conflict is difficult to establish under the current U.S. view of customary international law. There is little or no evidence of perfidy violations being prosecuted under international law in non-international armed conflicts, nor is there clear opinio juris by States on this matter.