<p>Why do legal norms obligate? This paper offers a structural response grounded in insights from the contractarian tradition. It introduces the <i>Legitimacy Matrix</i>, a conceptual model that explains legal normativity as emerging from institutional structures that simulate or instantiate mutual justification between norm source and norm subject. Abstracting from classic social contract theory, the framework generalises its core insight: that obligation arises not from consent, coercion, or moral truth alone, but from the intelligibility of justificatory relations. The paper identifies two dimensions, agent (actual or symbolic) and contract (actual or symbolic), generating a theoretic architecture of structural arrangements through which legal obligation is produced. Rather than departing from existing jurisprudential theories, the model clarifies why they diverge: each implicitly privileges a different quadrant of this structure. The framework reveals grounds of compatibility across traditions and offers a unified account of normativity that explains why courts often feel more legitimate than parliaments, why constitutions bind even when unwritten, and why some norms obligate without enforcement. Through comparative case studies, the paper demonstrates the framework’s explanatory power, enabling a principled account of both national and international legal obligation. Law binds, we submit, when its structure makes obligation intelligible.</p>