The Philippines is an Asian rule of law success story: an authoritarian state that transitioned peacefully to democratic, civilian rule. But the real test comes in 2013-14, when the Acquino administration finalises a peace settlement with separatists in Mindanao, an autonomous Muslim majority region. The settlement means de facto federalism: Islamic and customary legal norms will no longer be marginalised. Whose rules will prevail in post-conflict Mindanao? With what effect? By mapping today’s legal institutions in Mindanao we can better predict the future of rule of law in the Philippines, and the range of trajectories for peace-building in post-conflict societies.