The feasibility constraint on the concept of justice roughly states that a necessary condition for something to qualify as a conception of justice is that it is possible to achieve and maintain given the conditions of the human world. In this paper, I propose three alternative interpretations of this constraint that could be derived from different understandings of the Kantian formula ‘ought implies can’: the ability constraint, the motivational constraint and the institutional constraint. I argue that the three constraints constitute (...) a sequence in the sense that accepting the motivational constraint presupposes that we accept the ability constraint, and to accept the institutional constraint presupposes that we accept both previous constraints. Adding the possibility of rejecting all three constraints, we get four distinct metatheoretical positions that theorists could take vis-à-vis the feasibility constraint on justice. (shrink)