The rule of law is indispensable for sustained peace, good governance, and economic growth, especially in countries recovering from civil war. Yet for all its importance, the rule of law has received surprisingly little attention from political scientists and international relations scholars. This book proposes a new theory to explain how international organizations can restore the rule of law in the world’s weakest and most war-torn states, focusing in particular on the crucial but underappreciated role of the UN. The book tests the theory by combining analysis of original, highly disaggregated survey data from Liberia with cross-country analyses spanning all post-conflict countries in Africa since 1989. The book combines these quantitative results with qualitative insights gleaned from hundreds of interviews with UN officials, local leaders, citizens, and government and civil society representatives in Liberia and beyond. The book shows that UN intervention can have a deeper, more lasting, and more positive effect on the rule of law than the prevailing pessimism would lead us to believe.