Abstract Despite apparent agreement on the approach to the interpretation of statutes in Canada, a system of limited parliamentary sovereignty, judges differ on a fundamental point: how purpose is used in interpretation. Some judges craft arguments that view the text as the medium through which the legislature expresses its intention, using purpose to shed light on the meaning of the text in defined ways (‘text-as-medium’ interpretation). Others see the background purposes or values of the statutory context as binding constraints in a coherent legal order, with text as merely a signal to meaning (‘purpose-as-medium’ interpretation). This paper argues that text-as-medium interpretation offers the most persuasive account of the use of purpose in interpretation, especially in a system of legislative sovereignty, which constrains interpretive choice. By bringing to light the commitments of these two interpretive arguments in the Canadian context for the first time, the paper also raises deeper normative questions about how to view legislation in a Westminster parliamentary democracy. These questions are fundamental to the relationship between sovereign legislatures and courts.