The Rawlsian model of public justification is proposed for the assessment of politics of moral enhancement, in alternative to the neo-republican model proposed in these debates by Robert Sparrow. The central idea of the Rawlsian model of public justification is represented by the liberal principle of legitimacy, although it is extended in relation to the domain that Rawls sees as proper for its application (constitutional essentials). The liberal principle of legitimacy in its extended application requires that a law or public policy be justified on the base of reasons for which we can reasonably expect that other citizens can accept as free and equal citizens. The application is extended to children as prospective agents, as well. From the standpoint of the liberal principle of legitimacy, valid public reasons put forward in the moral enhancement debate are represented by the assessment of whether emotional modulation is progressive or regressive in relation to the capacity of moral judgment. The conclusion is that, at the actual stage of the debate, there are no victorious reasons to endorse any of the two proposals. Consequently, this is a domain of reasonable pluralism. Compulsory moral enhancement is ruled out, but mandatory moral enhancement is allowed. Usages of public funds for researches that concern moral bioenhancement are proper matter of democratic decision making.
