The capture of vast territories in Syria and Iraq by ‘Islamic State’ (IS or Da ‘ish) in 2013-14 placed civilian populations of several millions under the administration of an extremist Islamist (“jihadi”) insurgent group, whose brutal practices brought it worldwide notoriety. While in some ways unique this development is nevertheless emblematic of the new visibility of rebel groups, and in particular jihadi insurgents, as temporary rulers of civilians, highlighted also by recent similar cases in Somalia, Yemen, Mali and Afghanistan. Taken together, it demonstrates the importance of understanding not only why jihadis makes governance a priority, but also how they go about ruling and administering civilians. This paper examines how Da‘ish administered justice in its areas of control. Our starting point is the obvious dilemma which Da‘ish faced when seeking to balance between its ideological imperatives of imposing utterly extremist interpretations of Shari‘a on a large civilian population on the one hand and the military dictates of war requiring civilian consent and compliance on the other. Existing accounts on Da ‘ish administration of justice are highly contradictory, ranging from claims of widespread popular support for its harsh, but effective rule, particularly in its early phases, to portrayal of the Da‘ish justice as arbitrary, brutal, corrupt and universally rejected. This variation may suggests that IS justice system was far from uniform, as often assumed, but quite complex, flexible and adaptive to local contexts, and that it changed considerably over time, responding to changes in local power balances and Da‘ish military fortunes. One focal point for understanding how Da‘ish adapted its justice system to local context is to examine to what degree IS allowed customary law and conflict resolution mechanisms continue to exist in its areas of control. Drawing upon a vast collection of jihadi primary sources, media reports, court documents, and author interviews with civilians who lived under Da ‘ish rule in Iraq and Syria, this paper will explore Da‘ish administration of justice in Iraq and Syria with a specific focus its relationship to tribes and other local kinship-based organizations in the administration of justice. It asks questions such as to what degree did Da‘ish allow for local autonomy in the field of law enforcement and conflict resolution? When and under which circumstances were tribal leaders permitted to retain their positions as mediators in local conflict resolutions?