The ethical basis of suicide prevention is illustrated by contrasting helpline emergency rescue policies of the Samaritans in the UK and the US National Suicide Prevention Lifeline network. We contrast moralist, relativist and libertarian ethical premises and question whether suicide can be rational. Samaritans respect a caller’s right to decide to die by suicide; US helplines oblige emergency intervention during an attempt even against the caller’s will. We analyse the effect of emergency rescue when there is high suicide risk but an attempt has not been initiated. Issues of legal imperatives, jurisprudence and leeway given to helpers are analysed. We examine links between values and actions, the need for empirical evidence to guide practice, and propose vigorous dialogue about values in the grey zone of moral practice.