District of Columbia v. Heller ruptured the one institution—the militia—that courts had used for centuries to implement the right to keep and bear arms. If the question was “what arms?,” one looked to the militia to find an answer; if the question was “whose arms?,” again, one looked to the militia. Heller loosened the fit between the militia and the right, causing a welter of conflict as to what institutions now facilitate and constrain the Second Amendment. This Article attempts to restructure the inquiry into Second Amendment rights by drawing from the literature on institutionalism and constitutional law. Although the institutional turn in constitutional law has been important to free speech scholarship, religion clause scholarship, and separation of powers scholarship, no one has consciously applied institutionalism to the Second Amendment. This Article fills that gap. In so doing, it situates institutionalism within the leading methodological approaches of today: textualism, originalism, common law constitutionalism, popular constitutionalism, and pragmatism. As such, this Article aims to reach beyond Second Amendment scholars and speak more generally to debates about constitutional law and constitutional theory.