Scott Shapiro has posted Totally Exclusive Positivism on SSRN. Here is the abstract:
Recent controversies among inclusive and exclusive legal positivists have focused on the question whether the social facts that determine legal content can incorporate moral norms. Inclusive legal positivists, notably Jules Coleman, have argued that such incorporation is consistent with the conceptual structure of law. Exclusive legal positivists, including Joseph Raz, have argued that such incorporation is inconsistent with an essential conceptual feature of law, namely that law claims legitimate authority, which requires that the law be capable of providing reasons for action that avert the necessity for direct reliance on moral reasons. Although this discussion has continued for quite some time, none of the participants in the debate has noticed the significance of the fact that neither exclusive nor inclusive legal positivism results in actual exclusion of moral reasons from the content of legal deliberations. Framed in terms of H.L.A. Hart's theory of the core and penumbra, this point can be expressed as follows: in the penumbra, judges and other law appliers have discretion to rely on moral considerations in the resolution of vagueness in existing rules, as the basis for the creation of new rules, or as a ground for the resolution of contradictions between discordant elements of the existing rule set. For this reason, all existing versions of legal positivism do not provide a potent principle of exclusion: such theories can be called "impotent positivisms."
The alternative to impotent positivism is offered by the planning theory of law. The planning theory of law is based on the insight, familiar from the work of Michael Bratman, that plans can provide content-independent reasons for actions. In previous work, I have demonstrated that law can be understood on the model of plans. In this Article, the planning theory is deployed to develop a legal positivsim that provides a potent principle of exclusion. I demonstrate that the planning theory of law leads to the conclusion that morality can never be considered in the execution or interpretation of the plan (where the plan refers to the complete set or code of laws). This leads to the principle of total exclusion: law can only be coherently understood as providing content-independent reasons for action if moral considerations are totally excluded once the plan is set by the planning committee (or legislature).