Critics of public reason liberalism often object that a commitment to the public justification of law is too conservative: It prohibits the passage of controversial reforms. Laws that would promote justice are thwarted by recalcitrant but reasonable citizens. This objection presupposes a popular but empirically false theory of legal regulation on which laws affect behavior primarily through the threat of punishment. Against this position, this chapter argues that laws effectively regulate behavior when they cohere with social norms but are typically ineffective and sometimes counterproductive when they conflict with them. And laws and social norms are stable only when they approximate public justification. So, laws do not possess the autonomy and power that critics of public reason liberalism suppose. Without public justification, justice is difficult to secure and, if secured, is all-too-likely to be fragile.