The Principle of Legality: Issues of Rationale and Application

The term ‘principle of legality’ has most commonly been associated with one particular common law interpretive principle — the presumption that Parliament does not intend to interfere with fundamental common law rights, freedoms and immunities. The rationale is that it is in the last degree improbable that Parliament would abrogate or curtail such matters without clear and unambiguous language. The principle of legality is concerned with actual legislative intention. In recent times, it has been argued that a competing rationale has emerged, and the rationale of the principle is also facing contemporary challenges. In light of this, the nature and conceptual basis of the principle is briefly discussed. Moreover, the principle of legality, despite being long established, has been criticised for lacking clarity in its scope and operation. The purpose of this article is to comprehensively examine the principle’s scope and operation, having regard to the above-mentioned issues of rationale. This article focuses on the subject matter protected by the principle and the principle’s strength, including whether justification and proportionality considerations can have any role to play. It identifies and analyses methodological issues which remain unsettled, reaches conclusions as to methodological inconsistencies between the principle’s rationale and its application in practice, and provides some suggestions as to how this might be rectified.