Ethics committees like Institutional Review Boards and Research Ethics Committees are typically empowered to approve or reject proposed studies, typically conditional on certain conditions or revisions being met. While some have argued this power should be primarily a function of applying clear, codified requirements, most institutions and legal regimes allow discretion for IRBs to ethically evaluate studies, such as to ensure a favourable risk-benefit ratio, fair subject selection, adequate informed consent, and so forth. As a result, ethics committees typically make (...) moral demands on researchers: require them to act in a way the committee considers ethically right or appropriate. This paper argues that moral demands are legitimate only if publicly justifiable; and as a result, committee decisions are subject to a public justification requirement. Ethics committees can permissibly request for more information, changes to the research protocol or that the research is delayed or even stopped only if these demands are publicly justifiable. This latter claim is in turn justified on the basis that moral demands to φ are permissible only if we are in a position to know that the addressee ought to φ and that we are in a position to know a proposition only if it is publicly justifiable. This argument suggests that ethics committees must consciously and explicitly appeal to public reasons in their decision-making. In cases where public reasons cannot be offered, committees would not be permitted to reject a given study or make approval conditional on an amendment. (shrink)