There is intense debate over the legitimacy of interventions which seek behavioural change on the part of street homeless people. 'Hard' measures, such as arresting people for begging, are particularly controversial, but 'softer' interventions such as motivational interviewing have also prompted objections on grounds that they are paternalistic. At the same time, the 'non-interventionist' stance of some service providers has been accused of perpetuating harmful street lifestyles. Inspired by Ruth Grant's philosophically informed interrogation of the ethics of incentives, we propose a normative framework for application in this field. Via systematic exploration of Grant's three 'legitimacy standards' (legitimate purpose, voluntary response, effects on character), and an additional outcome-focussed fourth (effectiveness, proportionality and balance), we attempt to unsettle any intuitive assumption that noninterventionist approaches are necessarily more morally defensible than interventionist ones. We also, however, explicate the high ethical and empirical bar required to justify social control measures.