Australian legislatures and courts interact through the process of statutory construction. As part of this process, the principle of legality represents a subtle constraint by courts on Parliament. It is a rule of statutory interpretation that courts assume that Parliament abides by fundamental rights and freedoms and ‘the general system of law’ when it enacts legislation. When a court has a choice between different interpretations of a law, it will choose the interpretation which better accommodates these rights and freedoms, unless Parliament has clearly intended otherwise. The traditional justification of the principle of legality was an assertion about Parliament’s subjective intentions. However, in recent times, this justification has been discarded in favour of a more normative justification: the principle of legality is an onus placed on the legislature by the courts, which subtly guides Parliament to respect common law values.  This post puts forward two arguments. First, this justification for the principle of legality is not a recent development, but is consistent with and can be traced back to British constitutional law and its reception in Australia. Secondly, the principle is democratically legitimate because it is consistent with the constitutional role of the judicial branch of government in a liberal democracy.

The History and Principles Informing the Principle of Legality

Parliamentary supremacy is a cornerstone of Australian constitutional law. In Blackstone’s Commentaries, Sir Edward Coke described its power as ‘despotic’, and ‘transcendent and absolute.’ But the power of Parliament is not without constraint. Legislative power is constrained in the strict legal sense by the Australian Constitution. But in a more general sense, the supremacy of Parliament is premised on the rule of law. In his Introduction to the Study of the Law of the Constitution, A.V. Dicey spoke of the rule of law, through the common law, as a moderating influence on Parliament. While the two fundamental principles of Parliamentary supremacy and the rule of law seem to conflict, in reality the two facilitate each other. Parliament changes and enacts the law of the land flexibly and with democratic legitimacy, and the norms and values of the common law and the rule of law generally guide the Parliament in its law-making task. These values are essentially liberal values. The common law is ‘the law of liberty, of freedom and free peoples.’ Rights connected to personal liberty, such as the remedy of habeas corpus and rights connected with the criminal trial, are the result of the history of the common law. The relationship between Parliamentary supremacy and the rule of law articulated by Dicey is also present in the Constitution. While based on the English model in which parliamentary supremacy is a core principle, as Dixon J observed in Australian Communist Party v Commonwealth (1951) 83 CLR 1, the Constitution is also premised on the assumption of the ‘rule of law’. In Wik Peoples v Queensland (1996) 187 CLR 1 the common law was described as the ‘ultimate … foundation’ of the Constitution. So too are its liberal values and traditions.

In Australia these values have practical application in the law of statutory interpretation. In Zheng v Cai (2009) 239 CLR 446, the High Court explained that statutory interpretation was a key component of the constitutional relationship between legislature and the judiciary. Legislation is not simply a hollow proclamation, but exists to be applied and interpreted by courts. In the House of Lords case of Ex parte Pierson [1997] AC 539, Lord Steyn observed that Parliament does not legislate in a vacuum, but for a liberal democracy ‘founded on the principles and traditions of the common law’. These are, in the words of Pearce and Geddes, ‘liberal values shared by lawyers, legislators and the broader community.’ The principle of legality is what gives content to those values and traditions. It is enmeshed in the common law of statutory interpretation, its antecedents going back to 1772 and possibly earlier. To demonstrate the role of the principle as a normative influence on Parliament, it is critical to understand that this presumption is anterior to the subjective intent of the legislator.

The Competing Justifications for the Principle of Legality

The traditional justification

The earliest authority in Australia using the principle dates from 1908. In Potter v Minahan (1908) 7 CLR 277, O’Connor J held that it was ‘improbable’ Parliament would ‘intend’ to abrogate fundamental rights or depart from the general system of law, without expressing itself with ‘irresistible clearness.’ Justice O’Connor’s decision was the source of the ‘traditional justification’ for the principle of legality (Brendan Lim, ‘The Rationales for the Principle of Legality’ 2, 5).  This justification relies on a view of statutory interpretation as a deductive search for Parliament’s intent.

The problem with this rationale is that Parliament cannot actually have an ‘intention’, as Parliament itself is an artificial composite entity. Even if it did, it is unlikely that Members of Parliament, many of whom are not lawyers, have read or fully understood the legal nuances of what they are voting on when called to vote on a motion to read a Bill for a third time (Jeffrey Goldsworthy, ‘The Principle of Legality and Legislative Intention’ 46, 58-9). Additionally, the Australian legal system has fundamentally changed since 1908. We now live in a ‘statutory universe’. As McHugh J found in Malika Holdings Pty Ltd v Stretton (2001) 204 CLR 290, given the reach of the contemporary regulatory state, it can no longer be assumed that Parliament does not intend to abrogate fundamental rights. Given that the ‘traditional justification’ relies on an outdated view of statutory interpretation, an alternative justification is needed.

The normative justification

Speaking extra-curially, Justice Stephen Gageler has noted that the modern understanding of statutory interpretation is that intention is ascribed to Parliament constructively, based on the text and context of a statute, rather than interpretation being a deductive search for Parliament’s intent. This view of statutory interpretation also has historical antecedents. Dicey acknowledged that once a Bill received royal assent, while Parliament could amend it, its interpretation was entirely the court’s domain. He acknowledged that the process of statutory interpretation, informed by ‘the general spirit of the common law’, risked a construction of a statute which ‘would not commend itself … to the Houses of Parliament, if the Houses were called upon to interpret their own enactments.’ As this suggests, the view that statutory interpretation may lead to a result that does not reflect Parliament’s subjective intent predates Potter v Minahan. On this understanding, a better view of the principle of legality is that the central ‘intention not to abrogate rights’ is imputed to Parliament by the courts. When understood this way, the principle of legality is revealed to be a soft constraint on legislative power. This is the ‘normative’ justification of the principle.

The Legitimacy of the Normative Justification

The nature of the protection provided by the principle

The principle of legality facilitates legislative deliberation about traditional rights and freedoms, and in doing so forms a soft restraint on Parliament’s power. In Ex parte Simms [2000] 2 AC 115, Lord Hoffman held that the principle of legality placed an onus on Parliament, forcing it to have regard to fundamental rights and freedoms, and if it did not, to ‘squarely confront the political cost’ by using clear language to rebut the presumption provided by the principle. In Australia, this rationale is exemplified by the decision of a majority of the Mason Court in Coco v The Queen (1994) 179 CLR 427. Recent authority from the French High Court has approved of the majority’s justification of the principle in Coco, demonstrating that it remains an accepted rationale. This view of the principle of legality has been criticised as being incompatible with the proper relationship between Parliament and the courts. The remainder of the post will analyse this criticism.

The democratic critique

The principle of legality, premised on a normative justification, has been criticised as being counter-majoritarian and at odds with Parliamentary supremacy. This argument is that in a democratic system of Parliamentary supremacy, the court should be subordinate. In his book Parliamentary Sovereignty: Contemporary Debates, Jeffrey Goldsworthy, citing Dicey, argues that the traditional justification ‘was entirely consistent with parliamentary sovereignty,’ while by implication the normative justification is not. A view of the principle of legality as a structural onus placed on Parliament by the courts purportedly represents an undemocratic usurpation of the legislature by judges, specifically, a ‘manner and form requirement’ imposed by the judiciary.

It has also been criticised as a departure from the traditional role of the judiciary. In his dissent in North Australian Aboriginal Justice Agency v Northern Territory (2015) 256 CLR 569, Gageler J explained that a ‘strained’ application of the principle can amount to the court giving an unconstitutional ‘advisory opinion’ by allowing judges to articulate constitutional principles while the ‘real impact’ of those principles is ‘unfelt.’ There are two responses to this criticism. The first is that the principle of legality is entirely consistent with the constitutional role of the judiciary as a guarantor of the rule of law. The second is that when the normative role of the principle is properly understood as limited, it is entirely compatible with parliamentary supremacy.

The constitutional role of the court in a liberal democracy

The Parliament is not the sole institution that facilitates democracy. As an impartial arbiter of minority interests the court also has a legitimate role. The fundamental problem with a counter-majoritarian criticism is that its conception of democracy is too narrow. Liberal democracy does not mean simple majority rule. Lord Cooke of Thorndon, writing extra-curially, identifies that it must accommodate minority interests. Indeed, as explained in Blackstone’s Commentaries, being impartial and separate from the political branches of government, the judiciary is the guarantor of ‘public liberty’. An important component of the judicial department’s function in a tripartite system is to protect individual rights. Judicial functions including the exclusive determination and punishment of criminal guilt, and the process surrounding it, serve to protect the interests of the individual against a majoritarian democracy.

The role of statutory interpretation in the court’s constitutional role

Also falling within the judicature’s institutional check on the political branches of government is the task of statutory interpretation. As Chief Justice French has noted, statutory interpretation is the field in which the three branches of government interact in the exercise of their day-to-day functions. This role is exclusively the judiciary’s domain. As the principle of legality forms part of the law of statutory interpretation, it is understood as being imputed to Parliament.

At first glance, this may seem difficult to reconcile with the supremacy of Parliament within the Westminster system. However, Dicey acknowledged it was a legitimate constraint on legislative power that courts interpreted statutes consistently with the values of the common law rather than the subjective intention of Parliament. By encouraging Parliament to turn its mind to fundamental principles from the common law, including the protection of individual rights and freedoms, the judicature does not usurp its constitutional role.

The limited nature of the protection of rights

Critics of the normative justification of the principle of legality can overstate its strength or rigidity. It is argued to be a ‘common law constitution’ or ‘manner and form requirement’ imposed by judges undemocratically. While some argue the rule of law is superior to parliamentary supremacy, the principle of legality does not posit a bill of rights. The principle of legality promotes unenumerated rights and principles, but the protection it provides is subtle, and limited.

When properly understood, and as identified by the majority in Coco, rather than curtailing democracy, the principle enhances it, by promoting the rights and freedoms of the common law. As opposed to a positive mechanism for ensuring this outcome, such as a Bill of Rights, it is a mechanism that ensures the great power of the legislature is exercised, to quote Dicey, ‘in a spirit of legality’.

As held by French CJ in Momcilovic v The Queen, (2011) 245 CLR 1, the principle offers no hard constraint on legislative power, as it does not prohibit Parliament from altering rights and freedoms. It is not analogous to a manner and form requirement. This is because it is entirely within Parliament’s control to displace the principle, and not dependant on a certain majority in Parliament, or an electoral vote. Further, per Gleeson CJ in Al-Kateb v Godwin (2004) 219 CLR 562, the expression of legislative intent the principle encourages from Parliament requires no set form of words, and can be inferred from the object and purpose of the statute. When the principle of legality is understood as a soft normative constraint, ‘democratic’ criticism fails.


The principle of legality represents an important pillar of the structural relationship between Parliament and the courts in our constitution. The courts and Parliament mainly interact through statutory interpretation. As an important canon of statutory construction, the principle of legality gives content to the liberal tradition of the common law. As contemplated by Dicey, the principle of legality shows how parliamentary supremacy and the rule of law reinforce one another.


Dan Westbury is an undergraduate student at the University of Tasmania. This is an edited version of Dan’s 2017 Sir Anthony Mason Constitutional Law Prize winning essay.

Suggested citation:  Dan Westbury, ‘The Principle of Legality as a Reflection of the Constitutional Relationship between Parliament and the Courts’ on AUSPUBLAW  (19 February 2018) <>