In post-conflict settings where state and non-state legal orders coexist within the same territory in a situation of 'legal pluralism,' what factors determine individual preferences among alternative providers of justice and order? When and why do people choose to resolve disputes through non-state systems of adjudication-whether tribal or religious-rather than resorting to state police or courts? Does the type of dispute and the identity of the other party affect which legal system is chosen? Through a survey experiment conducted in the Iraqi city of Mosul, where the population has been exposed to three different justice systems--state, tribal, and the Islamic State's extreme interpretation of sharia-we explore the relationship between state legitimacy and support for non-state legal authorities. We also expect, among other hypotheses, that Iraqis who stayed in Mosul after the Islamic State (IS) arrived in June 2014 ('stayers') are more likely to prefer non-state legal authorities, whether tribal or Islamic, over state legal authorities in comparison with those who fled to government-controlled areas ('leavers'). Our results have important implications for efforts by governments to establish legitimacy in areas where their sovereignty has been challenged by non-state actors.