The author explores various theoretical approaches to the defence of necessity, rejecting both excusatory conceptions of the defence and those based on the notion of moral involuntariness. Rather, the author argues that necessity is properly understood as a justificatory defence based on a lack of moral blameworthiness. After extensively surveying the history of the defence in Canadian law, the author critiques the way in which the Supreme Court of Canada has restricted the defence. He contrasts the current Canadian approach with the treatment of the defence in other jurisdictions and concludes that Canadian law would be served best by a robust defence of necessity, which would acknowledge that, in some circumstances, pursuit of a value of greater worth than the value of adherence to the law can be justified.