  On this view, it is essential to law that the legality of a demand—its being grounded in institutional history in the right way—is a condition of its permissible enforcement. This is a claim that is at once metaphysical—a claim about the nature of law—and normative—a claim about the morality of coercion. It says that the correct explanation of why institutional history should have the role of constraint on coercive enforcement (a substantive normative explanation of a political ideal that makes history morally relevant to the permissible enforcement of claims) determines the correct explanation of how institutional history determines legal rights and obligations (the constitutive explanation of what it is, more precisely, for a claim of right and obligation to be grounded in institutional history in the legally appropriate way).