This book elaborates and defends the idea of law without the state. Animated by a vision of peaceful, voluntary cooperation as a social ideal and building on a careful account of non-aggression, it features a clear explanation of why the state is illegitimate, dangerous, and unnecessary. It proposes an understanding of how law enforcement in a stateless society could be legitimate and what the optimal substance of law without the state might be, suggests ways in which a stateless legal order could foster the growth of a culture of freedom, and situates the project it elaborates in relation to leftist, anti-capitalist, and socialist traditions.