Abstract
How can we explain compliance with international humanitarian law (IHL) by armed, non-state actors (ANSAs)? All parties to armed conflicts are bound by the IHL. Still, the expectations for rebel group compliance with international law are low, because they are, by definition, political entities fighting against existing authorities. There are, however, ANSAs which express their will to commit or comply with provisions of IHL. This thesis seeks to explore why, and under what conditions, ANSAs comply with rules of IHL. The observation that two apparently similar Muslim separatist groups operating in the south of the Philippines, display substantial variation with regards to use of violence against civilians provides the basis for a comparative case study. The Moro Islamic Liberation Front (MILF) has showed restraint in direct and intended killings of civilians not taking part in hostilities, while the Abu Sayyaf Group (ASG) has shown little willingness to do so. My analysis reveals that there are several causal relationships explaining the variation observed between the two groups. Through a theoretical framework for compliance behavior, I discover that social vulnerability, material vulnerability and degree of centralization can contribute to explain why MILF has demonstrated a higher degree of compliance with IHL than ASG.