Non-state actors, such as insurgents, rebel groups or dissident forces, militias, organizations led by warlords and criminal gangs, often bear the potential to disturb, undermine, or completely truncate processes of peace and State building, leading violence to flare up again. Such non-State actors often shape the situation during and after armed conflict in manifold ways. On the one hand, they are often perceived as responsible for violence against unarmed civilians in breach of human rights and humanitarian laws, as well as for the establishment of criminal and informal economies. On the other hand, they are often the expression of social problems because they see themselves as representatives of distinct interests and may build on broad support within communities. Modern military operations take place in complex environments characterized by challenges that affect the civilian population and host communities. Prominent among these challenges are displacement of civilian population, economic and infrastructure collapse with its attendant human suffering. Consequently, the military and other security agencies are confronted with non-combat tasks as a social responsibility to underscore the importance of managing the civil-military interface, along with humanitarian organizations, while working towards the restoration of peace and security in the area of operation. Nigeria, like most other nations stand the risk of external threats and aggression due to her vast economic resources and global political influence. However, her experience since independence in 1960 has shown a potent internal threat situation. The 1967-1970 Civil war was largely caused by internal political and ethnic antagonisms amongst the nation’s political class and disparate nationalities. After more than five decades as an independent nation these political and ethnic antagonisms rather than abate are exacerbated by various threats. These threats include ethnic militancy, religious fanaticism, electoral violence, rising poverty, youth unemployment, proliferation of small arms and light weapons, insurgency and various acts of terrorism. These challenges have often over stretched the capacity of Nigeria Police whose primary statutory duty it is to contain any internal crisis. However, the Armed Forces and other law enforcement agencies have the additional responsibility to assist civil authority in times of complex emergencies and violent conflicts. They also conduct domestic counter-insurgency and counter-terrorism operations for the stability of Nigeria. This is in addition to Nigeria’s involvement in peace support operations (PSO) and their attendant complex exigencies, including humanitarian assistance as may be requested by the ECOWAS, AU and UN. It is against this background that this paper seeks to achieve the following objectives: 1. To underscore the importance of understanding non-state actors, why and how they should be engaged;2. To clarify insurgency as a crime and a human rights violation;3. To examine the rationale and legal basis of Nigeria’s counter-insurgency/counter-terrorism measures;4. To explain the applicable rules relating to the legality for combating non-state actors; and 5. To conclude with viable options for Nigeria.