Private Law Theory

ABTRACT
This chapter charts the decline and fall of the principle of legality in the UK and Australia. It explains the significant ways in which courts in both jurisdictions have reined in the doctrine in recent years. These techniques include a more restrained approach to identification of norms that trigger the legality principle; subordination of the legality principle to so-called ‘ordinary’ methods of statutory interpretation; and integration of proportionality balancing in a way that downgrades protection of trigger norms. The result has been marginalisation of the legality principle in statutory interpretation, and weakened protection of basic norms.

The chapter explains why these changes have occurred from legal and contextual perspectives. The current retrenchment phase is a response to significant legitimacy concerns that arose due to over-expansion of the legality principle, including an undisciplined judicial approach to selection of trigger norms and judicial application of potent variants of the legality principle which involved departure from even clear statutory terms. Wider factors have also contributed, including the realpolitik of the COVID-19 pandemic, and broader economic, social and political trends which tend to favour subordination of individual rights to collective goals. On the other hand there are countervailing factors that may yet prompt reinvigoration of the legality principle, including the rise of populism.

The chapter argues that while the legality jurisprudence required course-correction, there has been an over-correction: the extent of the doctrinal shifts risks hollowing out the legality principle completely.

Ultimately the chapter argues for a re-focusing on the classic version of the legality principle, so as to re-establish the principle’s legitimacy. This involves (i) disciplined application of the legality principle, by limiting trigger norms to vested common law rights or other basic norms, the fundamentality, existence and contours of which are well-established by pre-existing legal authority; and (ii) maintaining the legality principle as a straightforward clear statement rule, insisting on clear statutory words before concluding that interference with fundamental norms is authorised.

Varuhas, Jason NE, The Principle of Legality: Decline and Fall (August 10, 2026) in J Boughey, LB Crawford and O Tamir (eds), Cambridge Handbook of Statutory Interpretation in the Common Law World (CUP).