This penultimate chapter turns to MacCormick’s institutional theory of law. This theory sought to answer questions about how law existed and how it was knowable. This chapter reads over four decades of this theory with character, doing so in two parts. In the first part, it explores the sense in which the very substance of the theory can be understood relationally, i.e., as underpinned by sensitivity to the dangers of domination, and a commitment to respect, decency, considerateness, and civility. The second part reads the institutional theory of law as a relational act in another sense, i.e., as mediating across what are otherwise often divisions or separations, such as between philosophy and sociology, or scholarship about law and the practice of law. The chapter tracks various changes in how MacCormick theorised law institutionally, from his early interest in law as institutional fact, to his later law as institutional normative order.