How do democratic societies establish and maintain order in ways that are conducive to growth? Contemporary scholarship associates order, democracy, and growth with centralized rule of law institutions. In this article, we test the robustness of modern assumptions by turning to the case of ancient Athens. Democratic Athens was remarkably stable and prosperous, but the ancient city-state never developed extensively centralized rule of law institutions. Drawing on the “what-is-law” account of legal order elaborated by Hadfield and Weingast (2012),we show that Athens’ legal order relied on institutions that achieved common knowledge and incentive compatibility for enforcers in a largely decentralized system of coercion. Our approach provides fresh insights into how robust legal orders may be built in countries where centralized rule of law institutions have failed to take root.