The paper examines and critically reflects on Neil MacCormick’s theory of legal reasoning, and more specifically with his theory of interpretation. To begin with, I will try to summarize the main tenets of MacCormick’s theory of legal interpretation; I will then move on to consider a specific interpretive problem, that is the place of defeasibility in law. Lastly, I will try to put these ideas in the context of MacCormick’s ideas on the Rule of law. The perspective of the examination is diachronical in character: I will try to highlight what seems to me a substantial evolution of MacCormick’s ideas on these topics, and to put this evolution in the broader context of MacCormick’s position within the jurisprudential camp.