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Zhou, Jack --- "Chapter III, Due Process And An Implied Guarantee Of Legal Equality" [2022] UNSWLawJlStuS 37; (2022) UNSWLJ Student Series No 22-37




Unlike numerous other constitutional systems, Australia lacks an express Bill of Rights which entrenches the principle of legal equality and non-discrimination.[1] In Leeth v Commonwealth,[2] two judges of the High Court, Deane and Toohey JJ, sought to locate a doctrine of legal equality under the law by way of a constitutional implication. This has been unsuccessful and such a doctrine has been decisively rejected in subsequent cases. However, it is submitted that a more limited equality, or equal justice, guarantee can be established, sourced from the requirements of Chapter III of the Australian Constitution (‘the Constitution’). Gaudron J’s dissent in Leeth formulated a narrower doctrine, based on the proposition that it would be incompatible with the notion of ‘judicial power’ under section 71 for a Chapter III court to exercise its powers in a discriminatory manner. Despite some support for this guarantee, there has not yet been a comprehensive pronouncement on its content and scope.

Part I of this essay considers the reasoning of the judges in Leeth v Commonwealth and subsequent cases with respect to the doctrine of equality. Because such a guarantee finds no express provision in the Constitution, this discussion recalls the Court’s interpretive approaches to constitutional implications. While it has been unwilling to draw a guarantee of substantive equality of peoples under the Commonwealth, Gaudron J’s formulation remains constitutionally viable. It has not been decisively rejected and even commands some support in subsequent cases.

Part II provides an account of this limited form of equality under the Chapter III framework of ‘judicial power’ and defends it from the view that the Constitution does not guarantee ‘substantive due process’. It considers an important distinction when discussions of equality and non-discrimination have emerged in the case law, namely that of substantive equality of persons under the law and more procedural forms of equality before the law. The limited equality guarantee eschews this by focusing on the structural requirements of ‘judicial power’ and the conduct of courts. Part III argues that this guarantee is compatible with the High Court’s jurisprudence on Chapter III more broadly, particularly with respect to due process protections. It draws from commentary that have identified a particularly functionalist approach to interpreting Chapter III which emphasises the normative values underlying it. A limited equality guarantee accords with key values such as the separation of judicial power and the integrity of the judicial process. Part IV attempts to formulate a workable constitutional test for this implied guarantee, based on extant precedent and considerations of the federal structure of the judiciary. It proposes a substance-based test for discrimination and a defeasible application of the guarantee where the discrimination is ‘appropriate and adapted’ for a legitimate purpose.


The landmark attempt to formulate an implied constitutional guarantee of legal equality was made in Leeth. A Commonwealth law, section 4(1) of the Commonwealth Prisoners Act 1967 (Cth),[3] empowered a court to fix non-parole periods for federal offenders, not exceeding the minimum non-parole periods of the States or Territory in which the offender was convicted. This had the result that a minimum sentence differed depending on the State or Territory – some states imposed significantly lower non-parole periods than others. Mr Leeth was convicted for offences under the Customs Act 1901 (Cth) and was sentenced with a minimum non-parole period under section 4 in accordance with Queensland’s non-parole periods. It was argued that the Act was impermissibly discriminatory because federal offenders in like circumstances would receive differing non-parole periods depending on the State or Territory of their conviction.

Section 4 of the Act was upheld by a 4:3 decision. Three judges in the majority, Mason CJ, Dawson and McHugh JJ, held that the law was within power and did not infringe any constitutional principle. Even if the law was discriminatory, their Honours held that ‘[t]here is no general requirement ... that Commonwealth laws should have a uniform operation throughout the Commonwealth’.[4] Their Honours also considered the impact of the federal system of criminal justice on sentencing, which necessarily differs in practice according to state by state.[5] Brennan J joined the majority for different reasons, considering that the provision did not involve judicial power, as the granting of parole was an executive function.[6] Nevertheless, his Honour did appear open to the possibility of an implied equality guarantee, but considered any discrimination resulting from section 4 justified by the system of penal administration that relied on the states.[7]

The three judges in the minority recognised some form of equality guarantee in the Constitution. Deane and Toohey JJ expressly identified a more general equality doctrine which would affect the substantive content of laws. Their Honours relied on an accumulation of factors, ranging from specific non-discrimination guarantees (sections 51(ii) and 117),[8] the common law’s general conception of legal equality,[9] and the nature of the federal compact,[10] to establish a ‘doctrine of the underlying equality of the people of the Commonwealth under the law and before the courts’.[11] Section 4(1), by treating federal offenders in like circumstances in a discriminatory manner, infringed this principle and was invalid.

Gaudron J also dissented but on a different basis than Deane and Toohey JJ’s implied equality doctrine. For her Honour, section 4(1) of the Commonwealth Prisoners Act raised ‘the much narrower issue of whether the Parliament may require a [Chapter III court] to exercise a power by reference to a criterion or to criteria which will necessarily result in discrimination’.[12] Accepting that the fixing of non-parole periods could form the subject of ‘judicial power’,[13] Her Honour focused on the requirements of section 71 of the Constitution and its vesting of ‘judicial power’ in Chapter III ‘courts’.[14] In determining whether section 4(1) was compatible with Chapter III, her Honour formulated a requirement that ‘judicial power’ could not be exercised in a discriminatory manner. Because section 4(1) made the State or Territory non-parole periods the ‘dominant consideration’ in the exercise of discretion it conferred, it failed to treat like offences alike.[15] Section 4(1) ‘would necessarily involve impermissible discrimination’ and it could not be ‘part of the judicial power of the Commonwealth’.[16]

Since Leeth, numerous judges have rejected a broad guarantee of legal equality under the Constitution of the kind put forth by Deane and Toohey JJ. This included Brennan J (now Chief Justice), Dawson, Gaudron, Gummow and McHugh JJ in Kruger v Commonwealth.[17] The proposition that there is no requirement that Commonwealth laws have a uniform operation was also endorsed in Putland v The Queen.[18] Nevertheless, in Kruger, Gaudron J reaffirmed her position in Leeth, stating that

Ch III operates to preclude the conferral on courts of discretionary powers which are conditioned in such a way that they must be exercised in a discriminatory manner. ... There is a limited constitutional guarantee of equality before the courts, not an immunity from discriminatory laws ...[19]

Her Honour’s narrower formulation of the equality guarantee not directly contracted by the majority in Leeth.[20] There are also dicta by other judges that appear to align with the fundamental aspects of her Honour’s reasoning. In Cameron v The Queen,[21] McHugh J said:

If there is one principle that lies at the heart of the judicial power of the Commonwealth, it is that courts, exercising federal jurisdiction, cannot act in a way that is relevantly discriminatory.[22]

These remarks were dicta as this particular issue was not argued.[23] Since Cameron, the status of this limited implied equality guarantee has not been further developed by the High Court. Judges and commentators have nevertheless considered Gaudron J’s equality doctrine open for further development.[24]


A cornerstone of the rule of law is the principle of legal equality.[25] Yet there are competing accounts of this; it can be taken to mean that all subjects have equal protection of the law and that the law cannot be discriminatory in its content or application.[26] In this context, an important distinction is that of substantive as opposed to procedural equality. The former connotes equality under the law, such that the substantive content of laws enacted by parliament cannot operate in a discriminatory manner.[27] However, procedural equality before the law focuses more on the judicial process and conduct of courts.[28] It must be emphasised that the implied guarantee formulated by Gaudron J in Leeth excludes substantive forms of equality, which may allow for its acceptance by the High Court.[29]

There are numerous conceptions of equality and non-discrimination contained in the Constitution,[30] but a general doctrine of equality has struggled to find acceptance. Indeed, historical or originalist considerations strongly militates against a broad doctrine of equality. There is scant historical support from the drafting of the Constitution in favour of this, where an Equal Protection clause drawn from the Fourteenth Amendment of the United States Constitution was vocally rejected.[31] Despite certain express provisions prohibiting discrimination in particular subject-matters, the Constitution still permits substantive discrimination on its citizens,[32] with the races power – section 51(xxvi) – furnishing the most conspicuous example of this.[33] Amelia Loughland has shown that the High Court’s jurisprudence has made unlikely any broad constitutional protection for ‘discrete and insular minorities’ from a majoritarian legislature in the form of an equality guarantee.[34]

In relation to Chapter III, judges have consistently denied the possibility of ‘substantive due process’ under the Constitution, which would import an equality guarantee.[35] The most extensive discussion was that of Dawson J in Kruger, who considered that

it is possible to regard the separation of judicial power from the other powers of government as affording a measure of due process but it is due process of an essentially procedural rather than a substantive kind ... Ch III contains no warrant for regarding a law as invalid because the substantive rights which it confers or the substantive obligations which it imposes are conferred or imposed in an unequal fashion.[36]

However, this would assume that notions of equality are invariably tied to the ‘substantive due process’ doctrine. The link may the product of the United States’ jurisprudence on the Fourteenth Amendment’s Equal Protection clause, which is said to apply to the federal government by virtue of the ‘due process’ clause of the Fifth Amendment.[37] His Honour’s characterisation is more relevant to the broader equality implication advocated by Deane and Toohey JJ in Leeth, but it does not undermine Gaudron J’s proposition of a ‘narrower formal limitation on the exercise of judicial power’.[38]

At any rate, the procedural/substantive due process dichotomy is uneasy to maintain,[39] as the court may be confronted with seemingly procedural matters that will affect substantive outcomes, such as rules of evidence, burdens of proof and other ‘quasi-substantive’ issues.[40] Rather, it is more useful in this context to focus on the notion of ‘judicial power’, particularly where a court is vested with a discretionary power and is also directed to exercise it in a prescribed manner.[41] Such discretion must be circumscribed and exercised judicially,[42] and, in Nicholas v The Queen, Gaudron J also considered equality as an essential feature of ‘judicial power’.[43] Denise Meyerson has suggested that Gaudron J’s equality guarantee in Leeth ought to ‘closely follow the contours of natural justice’ as between parties during proceedings.[44] However, this equality guarantee should not be limited to matters affecting the conduct of curial proceedings. Her Honour’s treatment of s 4(1) of the Commonwealth Prisoners Act in Leeth shows that it should apply to the exercise of judicial power generally. Accordingly, courts cannot exercise its powers upon a subject unfairly, singling them out beyond what is reasonably necessary for a legitimate purpose.[45] Section 71 requires that ‘judicial power’

should be exercised in accordance with the judicial process ... All are equal before the law. And the concept of equal justice – a concept which requires the like treatment of like persons in like circumstances, but also requires that genuine differences be treated as such – is fundamental to the judicial process.[46]


Although Chapter III contains no express guarantees or prohibitions, it has been accepted that it impliedly guarantees certain forms of ‘due process’. Its textual basis is said to be the essential attributes of ‘judicial power’, which is ‘vested’ in Chapter III ‘courts’ by s 71 of the Constitution, and the separation of powers doctrine from the Boilermakers’ Case.[47] It has also been said that these principles form an important manifestation of the rule of law under the Constitution.[48] In Chu Kheng Lim v Minister for Immigration, Local Government and Ethnic Affairs, the Court held that a law cannot be ‘inconsistent with the essential character of a court or with the nature of judicial power’.[49] However, there is considerable uncertainty as to its scope,[50] and there is no general due process requirement.[51] The principle may now guarantee a fair trial,[52] natural justice,[53] and certain rules of evidence.[54] Parliament cannot enact bills of attainder,[55] and cannot, in general, provide for punitive non-judicial detention.[56] Moreover, legislative interference with judicial proceedings have been invalidated. [57] An implied equality guarantee of the kind advocated in this essay would be related to these other due process requirements.[58] Its primary concern is the exercise of discretionary powers of a court, so that while parliament may of course regulate a Chapter III court’s powers,[59] it would be incompatible if it would cause a court to act in a discriminatory manner.[60]

Recognition of this guarantee is complicated by the fact that it is implied from the Constitution. Compared with Deane and Toohey JJ’s ‘liberal approach to constitutional implications’ in establishing their substantive guarantee of equality in Leeth,[61] the High Court has since become notably hesitant in drawing implied constitutional rights as opposed to more structural doctrines.[62] This ‘structure-rights dualism’, which might be attributed to legal-cultural factors and a doctrinal fixation on the ‘text and structure’ of the constitutional document,[63] has prevented an expansion of implied constitutional rights.[64] It is worth noting that Chapter III principles have often been considered a substitute ‘bill of rights’ by protecting these forms of due process.[65] George Winterton was sympathetic to this view but insisted that this should not include substantive rights, although he considered that Chapter III would ‘invalidate Commonwealth legislation which required a court to enforce laws inconsistent with civilised standards of humanity and justice’, such as manifestly excessive criminal sentences.[66] Nevertheless, the line of authority following Leeth has decisively rejected a broader, rights-based conception of equality.[67]

On the other hand, this more limited guarantee of equality applicable to Chapter III courts arguably has a more compelling textual basis as a structural limitation on legislative power.[68] It is connected with the other due process principles, which may not require a ‘rights-understandings of the separation of power[s]’.[69] The text of Chapter III along with the traditionally understood ‘methods and standards’ of the judicial process furnish the source for these implications.[70] It is based on the essential attributes of ‘judicial power’ vested by s 71 of the Constitution, and the strict separation of powers which: (1) makes only a Chapter III ‘court’ capable of exercising ‘judicial power’ and (2) a Chapter III court cannot exercise anything other than ‘judicial power’.[71] Against this background, the limited equality guarantee can be plausibly accommodated by the structural requirements of Chapter III. The position advocated in this essay is thus less radical than it seems despite the language of ‘equality’ and ‘non-discrimination’, which are evocative of more contentious constitutional rights.[72] It is better conceived as a limitation on governmental power imposed by the Constitution’s requirement of an independent judiciary exercising ‘judicial power’. The limited equality guarantee’s association with Chapter III limitations on interference with the judicial function thus provides a more secure basis for its acceptance.

1 Functionalism and Chapter III

Equal justice, as a matter of principle, is also consistent with prominent approaches to interpreting Chapter III. Peter Gerangelos and Rebecca Ananian-Welsh have advocated for a purposive formalist interpretation of Chapter III,[73] shifting away from the more purely formalistic approaches to the separation of powers doctrine.[74] While they emphasise categorical definitions of ‘judicial power’ in their application of the doctrine, they resort to the values of judicial impartiality and independence where they prove ambiguous.[75] However, functionalism has also played an important role in approaching Chapter III, with its emphasis on interpreting the Constitution in a manner that expressly recognises and gives effect to particular values,[76] in addition to engaging with formal legal sources.[77] This is of particular importance because some members of the High Court appear to have exhibited this interpretive methodology in Chapter III cases.[78] Recently, in Minister for Home Affairs v Benbrika,[79] Gageler and Gordon JJ seemed to adopt a more functionalist reading of Chapter III in their analysis of continuing detention orders, drawing on fundamental values,[80] namely, the liberty of the subject.[81] Other important values are recognised to include judicial independence and impartiality,[82] as well as the protection of the subject from governmental power through judicial processes.[83]

Equal justice and the non-discriminatory exercise of judicial power are consistent with these values, ‘especially so where the liberty of the individual is at stake’.[84] But aside from its connection with the attributes of ‘judicial power’, discussed above in Part II, the principle could play a constitutionally important role. The integrity of the judicial process would be compromised if a court was to exercise its powers in a way that discriminates against a person or class of persons. Such a concern is apparent in the development of the Kable ‘incompatibility’ principle: state laws that have conferred powers on courts singling out individuals or groups as the subject of court orders are considered a significant factor in the incompatibility analysis.[85] Although this applies at the state level and the inquiry is concerned with the ‘institutional integrity’ of state courts (rather than the more formal attributes of judicial power), this particular line of Kable doctrine cases are ‘likely to be integrated with the due process line of cases in this respect’.[86]

A further reason why such a limited equality guarantee is justified is that it will effect another underlying value that informs the separation of powers doctrine, namely as a check and balance against arbitrary authority.[87] This value is borne out in the original formulation of Boilermakers doctrine, which had the rationale of an independent and impartial judiciary in order to determine the respective powers of the states and the Commonwealth.[88] The framers of the Constitution were alert to the possible abuse of legislative authority by laws that affect or regulate the judicial process. Early commentators recognised this, such as William Harrison Moore, who described the nature of Chapter III’s separation of judicial power as a ‘safeguard against arbitrary power’.[89] Pragmatically, discrimination has been regarded as a readily identifiable manifestation of an infringement of a constitutional guarantee.[90] The insulation of ‘judicial power’ from incompatible powers assigned by the legislature (or executive) may thus be strengthened by a limitation that turns on the conferral of discriminatory powers.


Thus far, I have attempted to show that an implied equality guarantee sourced in Chapter III’s notion of ‘judicial power’ is both plausible as a matter of precedent and conformable with the High Court’s jurisprudence on Chapter III. The following is partly an attempted restatement of principle, discussing how this limited equality guarantee would operate as a free-standing constitutional rule. Certain conceptual issues arise with a test which turns on the concept of ‘discrimination’,[91] and there are also difficulties posed by the federal structure of the judicial system. Once again, functionalist considerations will play a role.

1 Discrimination and Uniformity in Federal Jurisdiction

This implied guarantee would take effect at the Commonwealth rather than state level, given its basis in the strict separation of judicial powers understood in the Boilermakers’ Case.[92] However, the cases which have discussed this notion of equal justice have unfolded against a more complex background involving the application of state laws and federal choice of law rules. While in Leeth, the impugned law was federal legislation operating as the ‘governing provision’,[93] in Cameron and Putland, the question was whether a state sentencing law could be picked up in federal jurisdiction. A possible objection to this limited equality guarantee is that it must account for the reality of the federal judicature system established by the Constitution. As Gummow and Heydon JJ cautioned, ‘to utter the term “discrimination” as a solvent to issues arising in a federal court structure itself dictates no easy or universal answer’.[94]

The laws of a state or territory wherein federal jurisdiction is exercised by a court of that state or territory are picked up by section 79 of the Judiciary Act 1903 (Cth) in order to regulate the exercise of federal jurisdiction.[95] Section 68 also performs a similar function where federal jurisdiction is exercised over federal offences,[96] such that state laws with respect to trial, conviction, and appeals – including sentencing[97] – are picked up. Thus, different outcomes in matters under federal jurisdiction may also produce discriminatory results, as state and territory laws conferring powers on courts will not only differ,[98] but will also not be subject to this implied equality guarantee.

This was the case in Putland, where a Northern Territory sentencing law was picked up by s 68 of the Judiciary Act to impose an aggregate sentence for multiple offences in a single indictment, subject to a prescribed maximum term. It was argued that this resulted in impermissible discrimination with other federal offenders, who would not have aggregated sentences. This argument was rejected, based on the majority decision in Leeth and the proposition that Commonwealth laws need not have a uniform application.[99] Gummow and Heydon JJ relied on the doctrine in Erie Railroad Co v Tompkins to suggest that the application of State law would better promote uniformity, even if it may produce different results in the Commonwealth as a whole.[100]

It must be recognised that this forms an area of uncertainty. Can a State law be picked up in federal jurisdiction if imposes legal consequences based purely on the State in which those proceedings take place?[101] In Cameron, a Western Australia District Court judge had sentenced an offender while exercising federal jurisdiction, as the offence took place in a Commonwealth place (ie, Perth Airport). The offender received a discount on his sentence, which was provided by section 8 of Western Australia’s Sentencing Act 1995 for early guilty pleas. That law was picked up by the Commonwealth Places (Application of Laws) Act.[102] As noted in Part I, based on the principle of equal justice, his Honour doubted the ability for state laws to be picked up in federal jurisdiction if it would cause a Chapter III court to operate in a discriminatory manner. His Honour considered it ‘at least arguable’ that sentencing mitigation provisions could not be picked up in federal jurisdiction.[103] If this limited equality guarantee is broadly accepted by the High Court, it could potentially operate to make state sentencing laws that provide varying discounts incapable of being picked up in federal jurisdiction. In this area of uncertainty, functionalist considerations may inform the scope of the implied legal equality guarantee and how it can be accommodated in the federal judicial structure. This will be considered in formulating a test for this implied guarantee.

2 A Test for Discrimination

The proposed test for this implied guarantee must contain a threshold question: this limitation would only apply to laws which regulate a Chapter III’s court’s exercise of ‘judicial power’. A general law conferring rights and obligations at large, though enforceable in Chapter III courts, would not be subject to this limitation. Without attempting an exhaustive definition of judicial power, it would embrace this can embrace all manner of discretionary court orders.[104] In practice, this would probably arise in sentencing cases, where judicial discretion consistently plays a significant role.[105]

The implied equality guarantee prohibits a Chapter III court from exercising its judicial power in a discriminatory manner. The concept of discrimination, in the relevant sense, can be drawn from other constitutional doctrines which are grounded on notions of equality and non-discrimination, such as the current approaches to sections 92 and 117 of the Constitution.[106]

A law that places a discriminatory burden on a particular litigant or class of litigants may well attract scrutiny under this rule.[107] The enacting of unfair processes may also amount to discrimination.[108] But taking ‘discrimination’ as the basis of a constitutional test raises further issues. Should the test be concerned with formal or substantive discrimination?[109] On one hand, Deane and Toohey JJ in Leeth doubted whether section 4(1) of the Commonwealth Prisoners Act could engage the limited equality guarantee grounded in Chapter III because it was addressed to courts in undifferentiating terms to apply the single set of local parole laws.[110] On their Honours’ construction, section 4 did not ‘require ... a court to act unjudicially by discriminating on irrelevant or irrational grounds’.[111] This may have led them to proposing a broader equality guarantee. On the other hand, Gaudron J preferred to regard the substance and effect of the provision – the criteria for the power’s exercise would necessarily result in discrimination based on the state and territory of the conviction.

If a functionalist perspective is adopted, the question of whether a formal/substantive non-discrimination test is appropriate should be answered in light of the values informing Chapter III discussed above. In her functionalist analysis of equality and non-discrimination principles under the Constitution, Amelia Simpson has pointed out that the form/substance dichotomy is better conceived as a spectrum, depending on the relevant doctrine and its underlying values.[112] Thus, section 99 of the Constitution, prohibiting preferences to the States, is better regarded as importing a form-based inquiry as the purpose of the provision is in ‘maintaining an appearance of even-handedness in this aspect of federal fiscal relations’.[113] Given Chapter III’s underlying values including the separation of powers, the integrity of the judicial process, and the protection of the subject, a more substance-based test is appropriate. The inquiry should be whether the court would practically treat a person or class of persons differently to those in like circumstances, even if the terms of the power are neutral on their face. Discrimination would involve an abrogation of the principle of treating like cases alike. As Gaudron, Gummow and Hayne JJ said in Wong v The Queen, while discussing the nature of a judge’s sentencing discretion, ‘[e]qual justice requires identity of outcome in cases that are relevantly identical. It requires different outcomes in cases that are different in some relevant respect.’[114] It would therefore not be open for a Chapter III court to exercise a power that fails to treat like cases alike or fails to account for genuine differences.

Nonetheless, it is clear that not all forms of discriminatory regulation of the exercise of judicial power should result in incompatibility with Chapter III. As the Court said in Austin v Commonwealth:

The essence of the notion of discrimination is said to lie in the unequal treatment of equals or the equal treatment of those who are not equals, where the differential treatment and unequal outcome is not the product of a distinction which is appropriate and adapted to the attainment of a proper objective.[115]

Thus, Gaudron, Gummow and Callinan JJ in Cameron found that application of the Western Australian law would not infringe equal justice requirements (accepting, provisionally, that such a requirement existed). Their Honours considered that discrimination would be prohibited if there was no ‘proper objective’ and if it was not ‘appropriate or adapted’.[116] Their Honours used the ‘appropriate and adapted’ formula, [117] citing Castlemaine Tooheys Ltd v South Australia,[118] to justify Western Australia’s sentencing discount regime. They were part of the state’s local sentencing practices that were said to facilitate the ‘course of justice’, which justified the differential treatment of offenders who plead guilty at the earliest opportunity.[119] It also appeared that the kind of legislation considered in Leeth attracted this type of inquiry. There, the majority judgment pointed out that, although consistency in the sentencing of federal offenders was desirable,[120] the administration of federal criminal justice relies heavily on the states.[121] This was contemplated by other express provisions in the Constitution such as sections 80 (trial on indictment to be held in the state where the offence was committed) and 120 (states to make provision for detention of federal offenders) such that state-based variations were inevitable.[122] In these cases, the suggestion seems to be that the requirements of the federal system of criminal justice and penal administration form legitimate purposes of discrimination.[123]

Functionalist considerations will also be of importance where the Court will be faced with these constitutional choices. In this regard, the test should account for these competing values:[124] on the one hand, Chapter III-values supporting the integrity of the federal judicial process, and, on the other hand, federalism-related values, or ‘judicial federalism’ as James Stellios has described it,[125] which emphasise the State’s interests in applying their own local sentencing regimes in the administration of their penal system. There is much force in the proposition that federal offenders should be treated consistently across the Commonwealth as a whole, as pointed out by Kirby J in Cameron and Putland.[126] However, a functionalist approach would consider the practical effects of invalidating these laws, taking into account the alternative regulatory regimes and actors that come with a federal system.[127] The High Court has noted that the federal judicial system provided ‘distinct alternatives’ for the legislature: it can either impose uniformity across the Commonwealth in dealing with federal offenders; or utilise the infrastructure of state courts and create uniformity within the state in its treatment of federal and state offenders.[128] The latter was the legislative choice taken.[129] The non-discriminatory exercise of judicial power would therefore be a defeasible limitation. It is questionable whether the differential treatment of federal offenders in these circumstances should be treated as invalid discrimination, given that there are also doubts as to whether certain state laws that provide for sentencing mitigation for guilty pleas apply to federal offences.[130]

Accordingly, the implied guarantee of legal equality in the exercise of judicial power would contain: (1) a substance-based inquiry into whether the conferral of power would cause a Chapter III court to act in a discriminatory manner; and (2) if such discrimination is found, whether it is appropriate and adapted to a legitimate purpose.


Although an implied constitutional guarantee of substantive equality is highly unlikely to be accepted, a more limited doctrine of legal equality, or equal justice, attached to the ‘judicial power’ vested in Chapter III courts remains tenable. Drawing from Gaudron J’s judgment in Leeth, this eschews a rights-based understanding of equality, in the nature of equal protection of the laws, in favour of a more limited, structural guarantee affecting the exercise of judicial power. Accordingly, discretionary power conferred on courts, such as the sentencing of federal offenders, cannot be exercised in a discriminatory manner. It is submitted that this conforms with the High Court’s jurisprudence on constitutional implications as well its approach to Chapter III due process principles. From a functionalist lens, the non-discriminatory exercise of judicial power gives effect to the values underlying Chapter III. Consistent with a functionalist reading which highlights the values of impartiality and the integrity of the judicial process, that discrimination should be assessed holistically, whether there has in effect been differential treatment even if the law appears to be of general application on its face. The proposed test for this guarantee also recognises its defeasible nature and is thus capable of taking into account competing values, drawing from the line of cases in which the federal system of criminal justice has grappled issues of discrimination and uniformity. In light of these, such an implied constitutional guarantee of legal equality calls for further examination.

[1] See, eg, Canada Act 1982 (UK) c 11, sch B pt I (‘Canadian Charter of Rights and Freedoms’) s 15; Convention for the Protection of Human Rights and Fundamental Freedoms, opened for signature 4 November 1950, 213 UNTS 221 (entered into force 3 September 1953) art 14; Constitution of India, 1950 (Ind) art 14; New Zealand Bill of Rights Act 1990 (NZ) s 19.

[2] (1992) 174 CLR 455 (‘Leeth’).

[3] The impugned provisions of the Commonwealth Prisoners Act 1967 (Cth) were repealed before the proceedings in Leeth, but his non-parole recommendation made under the former provisions were preserved by section 30(1) of the Crimes Legislation Amendment Act (No 2) 1989 (Cth). The latter amendment was also upheld by the Court in Leeth.

[4] Leeth (n 2) 467.

[5] Ibid 470.

[6] Ibid 476.

[7] Ibid 475–6; GJ Lindell, ‘Recent Developments in Constitutional Interpretation’ in Geoffrey Lindell (ed), Future Directions in Australian Constitutional Law (Federation Press, 1994) 1, 36 (‘Recent Developments’).

[8] Leeth (n 2) 484, 487.

[9] Ibid 486.

[10] Ibid 486.

[11] Ibid 492.

[12] Ibid 501.

[13] Ibid.

[14] Ibid 501; R v Kirby; Ex parte Boilermakers' Society of Australia [1956] HCA 10; (1956) 94 CLR 254, 289 (Dixon CJ, McTiernan, Fullagar and Kitto JJ) (‘Boilermakers’ Case’).

[15] Leeth (n 2) 500.

[16] Ibid 503.

[17] Kruger v Commonwealth [1997] HCA 27; (1997) 190 CLR 1, 44–5 (Brennan CJ), 112 (Gaudron J), 142 (McHugh J) 154 (Gummow J) (‘Kruger’).

[18] [2004] HCA 8; (2004) 218 CLR 174, 195 (Gummow and Heydon), 215 (Callinan J) (‘Putland’). See also Sweedman v Transport Accident Authority [2006] HCA 8; (2006) 226 CLR 362, 399 (Gleeson CJ, Gummow, Kirby and Hayne JJ).

[19] Kruger (n 17) 112. Gaudron J made similar remarks in Kable v Director of Public Prosecutions (NSW) [1996] HCA 24; (1996) 189 CLR 51, 107 (‘Kable’).

[20] Lindell (n 7) 37.

[21] [2002] HCA 6; (2002) 209 CLR 339 (‘Cameron’).

[22] Ibid 352 [44].

[23] Ibid 353 [47].

[24] Justice Michael McHugh, ‘Does Chapter III of the Constitution Protect Substantive As Well As Procedural Rights?’ (2001) 21 Australian Bar Review 235, 251–2; Denise Meyerson, ‘Equality’ in Cheryl Saunders and Adrienne Stone (eds), The Oxford Handbook of the Australian Constitution (Oxford University Press, 2018) 1053, 1057; James Stellios, Zines’s The High Court and the Constitution (Federation Press, 6th ed, 2015) 309 (‘Zines’s The High Court’); Fiona Wheeler, ‘Due Process, Judicial Power and Chapter III in the New High Court’ (2004) 32 Federal Law Review 205, 223–4 (‘Due Process, Judicial Power and Chapter III’).

[25] Brian Z Tamanaha, On the Rule of Law: History, Politics, Theory (Cambridge University Press, 2004) 64; Tom Bingham, The Rule of Law (Penguin, 2010) ch 5.

[26] See Lisa Burton Crawford, The Rule of Law in the Australian Constitution (Federation Press, 2017) ch 2; Hugh Collins, ‘Discrimination, Equality and Social Inclusion’ (2003) 66 Modern Law Review 16, 17–18.

[27] See, eg, Leeth (n 2) 487 (Deane and Toohey JJ); McHugh (n 24) 249–51.

[28] Will Bateman, ‘Procedural Due Process under the Australian Constitution[2009] SydLawRw 16; (2009) 31 Sydney Law Review 411, 422, 428–9; Crawford (n 26) 145.

[29] See Cheryl Saunders, ‘Concepts of Equality in the Australian Constitution’ in Geoffrey Lindell (ed), Future Directions in Australian Constitutional Law (Federation Press, 1994) 209, 229–30.

[30] Amelia Simpson, ‘The High Court’s Conception of Discrimination: Origins, Applications, and Implications’ [2007] SydLawRw 10; (2007) 29(2) Sydney Law Review 263, 264–6 (‘The High Court’s Conception of Discrimination’).

[31] John A La Nauze, The Making of the Australian Constitution (Melbourne University Press, 1972) 227–32; Meyerson (n 24) 1063; Jeremy Kirk, ‘Constitutional Implications (II): Doctrines of Equality and Democracy’ [2001] MelbULawRw 2; (2001) 25 Melbourne University Law Review 24, 38.

[32] John Quick and Robert Garran, The Annotated Constitution of the Australian Commonwealth (LexisNexis Butterworths, rev ed, 2015) 623 § 210.

[33] See Kartinyeri v Commonwealth [1998] HCA 22; (1998) 195 CLR 337, 357–8 [16]–[20] (Brennan CJ and McHugh J), 380 [86]–[87] (Gummow and Hayne JJ); Robert French, ‘The Race Power: A Constitutional Chimera’ in HP Lee and George Winterton (eds), Australian Constitutional Landmarks (Cambridge University Press, 2003) 180, 205–7.

[34] Amelia Loughland, ‘Taking Process-Based Theory Seriously: Could “Discrete and Insular Minorities” Be Protected Under the Australian Constitution?’ (2020) 48(3) Federal Law Review 324, 339–42.

[35] Lange v Australian Broadcasting Corporation [1997] HCA 25; (1997) 189 CLR 520, 566–7 (the Court).

[36] Kruger (n 17) 68.

[37] Erwin Chermerinsky, Constitutional Law: Principles and Policies (Wolters Kluwer, 2019) 724–5; Bolling v Sharpe, [1954] USSC 41; 347 US 497, 499 (1954).

[38] James Stellios, The Federal Judicature: Chapter III of the Constitution (LexisNexis Australia, 2nd ed, 2020) 356 [6.80] (‘Federal Judicature’).

[39] Chris Steytler and Iain Field, ‘The “Institutional Integrity” Principle: Where Are We Now, and Where Are We Headed?’ (2011) 35 University of Western Australia Law Review 227, 257–8.

[40] McHugh (n 24) 239.

[41] Stellios, Zines’s The High Court (n 24) 308.

[42] Fencott v Muller (1982) 152 CLR 570, 608 (Brennan and Deane JJ).

[43] [1998] HCA 9; (1998) 193 CLR 173, 207 (‘Nicholas’).

[44] Fiona Wheeler, ‘Due Process’ in Cheryl Saunders and Adrienne Stone (eds), The Oxford Handbook of the Australian Constitution (Oxford University Press, 2018) 928, 940.

[45] Leeth (n 2) 502.

[46] Ibid.

[47] Chu Kheng Lim v Minister for Immigration, Local Government and Ethnic Affairs (1992) 176 CLR 1, 27 (Brennan, Deane and Dawson JJ) (‘Chu Kheng Lim’); Polyukhovich v The Commonwealth [1991] HCA 32; (1991) 172 CLR 501, 607 (Deane J), 689 (Toohey J), 703–4 (Gaudron J) (‘Polyukhovich’).

[48] Wheeler, ‘Due Process, Judicial Power and Chapter III’ (n 24) 208.

[49] Chu Kheng Lim (n 47) 27 (Brennan, Deane and Dawson JJ); Bateman (n 28) 417.

[50] APLA Ltd v Legal Services Commissioner (NSW) [2005] HCA 44; (2005) 224 CLR 322, 411 (Gummow J); Wheeler, ‘Due Process, Judicial Power and Chapter III’ (n 24) 206–7; Stellios, Federal Judicature (n 38) 359–60 [6.88].

[51] Thomas v Mowbray (2007) 237 CLR 307, 355 (Gummow and Crennan JJ) (‘Thomas’).

[52] Dietrich v The Queen [1992] HCA 57; (1992) 177 CLR 292, 326 (Deane J), 362 (Gaudron J); Re Nolan; Ex parte Young [1991] HCA 29; (1991) 172 CLR 460, 496 (Gaudron J) (‘Nolan’); McHugh (n 24) 240–1.

[53] Bass v Permanent Trustee Co Ltd [1999] HCA 9; (1999) 198 CLR 334, 359 (Gleeson CJ, Gaudron, McHugh, Gummow, Hayne and Callinan JJ).

[54] Kable (n 19) 106–7 (Gaudron J); Nolan (n 52) 496–7 (Gaudron J); Leeth (n 2) 487–8 (Deane and Toohey JJ); Assistant Commissioner Condon v Pompano Pty Ltd (2013) 252 CLR 38, 99–101 (Hayne, Crennan, Kiefel and Bell JJ), 104–5 (Gageler J).

[55] Polyukhovich (n 47) 536 (Mason CJ), 684–9 (Toohey J); 721 (McHugh J).

[56] Chu Kheng Lim (n 47) 34 (Brennan, Deane and Dawson JJ), 71 (McHugh J).

[57] See Peter Gerangelos, ‘The Separation of Powers and Legislative Interference in Pending Cases’ [2008] SydLawRw 3; (2008) 30(1) Sydney Law Review 61.

[58] Stellios, Federal Judicature (n 38) 350 [6.70].

[59] Nicholas (n 43) 186 (Brennan CJ).

[60] McHugh (n 24) 250; Amelia Simpson, ‘Equal Treatment and Non-Discrimination through the Functionalist Lens’ in Rosalind Dixon (ed), Australian Constitutional Values (Bloomsbury Publishing, 2018) 195, 202 (‘Equal Treatment’).

[61] Crawford (n 26) 148.

[62] Rosalind Dixon and Gabrielle Appleby, ‘Constitutional Implications in Australia Explaining the Structure – Rights Dualism’ in Rosalind Dixon and Adrienne Stone (eds), The Invisible Constitution in Comparative Perspective (Cambridge University Press, 2018) 343, 344.

[63] Ibid 343, 367, 359–62.

[64] Ibid 357.

[65] George Winterton, ‘Separation of Judicial Power as Implied Bill of Rights’ in Geoffrey Lindell (ed), Future Directions in Australian Constitutional Law (Federation Press, 1994) 185; Leslie Zines, ‘A Judicially Created Bill of Rights?’ [1994] SydLawRw 14; (1994) 16 Sydney Law Review 166, 167–75.

[66] Winterton (n 65) 207.

[67] Will Bateman et al, Hanks Australian Constitutional Law: Materials and Commentary (LexisNexis Australia, 2021) 1267–8 [10.4.13].

[68] Dixon and Appleby (n 62) 347, 350.

[69] Stellios, Federal Judicature (n 38) 619 [6.5].

[70] Thomas (n 51) 355 [111] (Gummow and Crennan JJ); Stellios, Federal Judicature (n 38) 320 [6.6].

[71] Boilermakers’ Case (n 14) 269–72 (Dixon CJ, McTiernan, Fullagar and Kitto JJ); Cheryl Saunders, ‘The Separation of Powers’ in Brian Opeskin and Fiona Wheeler (eds), The Australian Federal Judicial System (Melbourne University Press, 2000) 3, 11.

[72] Dixon and Appleby (n 62) 3438.

[73] See Rebecca Ananian-Welsh, ‘A Purposive Formalist Interpretation of Chapter III of the Australian Constitution’ (PhD thesis, University of New South Wales, 2014) 283; Peter Gerangelos, ‘Interpretational Methodology in Separation of Powers Jurisprudence: The Formalist/Functionalist Debate’ (2005) 8 Constitutional Law and Policy Review 1.

[74] Wheeler, ‘Due Process’ (n 44) 947–8

[75] Rebecca Welsh, ‘A Path to Purposive Formalism: Interpreting Chapter III for Judicial Independence and Impartiality’ 39(1) Monash University Law Review 66, 70, 78, 96.

[76] James Stellios, ‘Reconceiving the Separation of Judicial Power’ (2011) 22 Public Law Review 113, 120–1.

[77] Rosalind Dixon, ‘Functionalism and Australian Constitutional Values’ in Rosalind Dixon (ed), Australian Constitutional Values (Bloomsbury Publishing, 2018) 3, 9.

[78] Rosalind Dixon, ‘The Functional Constitution – Rereading the 2014 High Court Constitutional Term’ (2015) 43 Federal Law Review 455, 472 (‘The Functional Constitution’).

[79] [2021] HCA 4; (2021) 95 ALJR 166 (‘Benbrika’).

[80] Andrew Dyer, ‘Minister for Home Affairs v Benbrika and the Capacity of Chapter III of the Constitution to Protect Prisoners’ Rights’ [2022] UNSWLawJl 8; (2022) 45(1) University of New South Wales Law Journal 209, 236–7

[81] Benbrika (n 79) 189 [71]–[72] (Gageler J), 202 [138], 205–7 [143]–[160] (Gordon J).

[82] TCL Air Conditioner (Zhongshan) Co Ltd v Judges of the Federal Court of Australia (2013) 251 CLR 533, 553–4 [28] (French CJ and Gageler J); Sarah Murray, ‘Impartial Justice’ in Rosalind Dixon (ed), Australian Constitutional Values (Bloomsbury Publishing, 2018) 121, 122.

[83] Magaming v The Queen [2013] HCA 40; (2013) 252 CLR 381, 399–401 [61]–[67] (Gageler J).

[84] Leeth (n 2) 499 (Gaudron J).

[85] South Australia v Totani [2010] HCA 39; (2010) 242 CLR 1, 92–3 [235]–[236] (Hayne J).

[86] Stellios, Federal Judicature (n 38) 360 [6.89]; Wainohu v New South Wales (2011) 243 CLR 181, 213–14 [52] (French CJ and Kiefel J).

[87] MJC Vile, Constitutionalism and the Separation of Powers (Liberty Fund, 1998) 19–20.

[88] Boilermakers Case (n 14) 267–8 (Dixon CJ, McTiernan, Fullagar and Kitto JJ); R v The Federal Court of Bankruptcy; Ex parte Lowenstein [1938] HCA 10; (1938) 59 CLR 556, 588–9 (Dixon and Evatt JJ); Bateman (n 28) 432.

[89] William Harrison Moore, The Constitution of the Commonwealth of Australia (Maxwell, 2nd ed, 1910, reprint 1997) 322.

[90] Peter Hanks, Frances Gordon and Graeme Hill, Constitutional Law in Australia (LexisNexis Butterworths, 4th ed, 2017) 293 [5.43]; Graeme Hill, ‘Discrimination and the Melbourne Corporation Doctrine’ (2003) 14 Public Law Review 80, 83.

[91] Kirk (n 31) 135.

[92] James Stellios, ‘The Centralisation of Judicial Power within the Australian Federal System’ (2014) 42 Federal Law Review 357, 369 (‘Centralisation of Judicial Power’).

[93] Leeth (n 2) 462 (Mason CJ, Dawson and McHugh JJ).

[94] Putland (n 18) 196 [60].

[95] Judiciary Act 1903 (Cth) s 79; Rizeq v Western Australia [2017] HCA 23; (2017) 262 CLR 1, 25–6 [58], 27 [61]–[62] (Bell, Gageler, Keane, Nettle and Gordon JJ).

[96] Solomons v District Court (NSW) [2002] HCA 47; (2002) 211 CLR 119, 128 [3] (Gleeson CJ, Gaudron, Gummow, Hayne and Callinan JJ).

[97] Putland (n 18) 178–9 [4] (Gleeson CJ); Williams v The King (No 2) [1934] HCA 19; (1934) 50 CLR 551, 560 (Dixon J).

[98] See Australian Law Reform Commission, The Judicial Power of the Commonwealth: A Review of the Judiciary Act 1903 and Related Legislation (Report No 92, 2001) 560–1.

[99] Putland (n 18) 185 [25] (Gleeson CJ), 195 [59] (Gummow and Heydon JJ), 215 [122] (Callinan J).

[100] Ibid 195–6 [60], citing Erie Railroad Co v Tompkins, [1938] USSC 94; 304 US 64, 74–5 (1938).

[101] This problem would influence the High Court’s development of common law choice of law rules, particularly choice of law for intrastate torts: Breavington v Godleman [1988] HCA 40; (1988) 169 CLR 41, 88 (Wilson and Gaudron JJ); John Pfeiffer Pty Ltd v Rogerson [2000] HCA 36; (2000) 203 CLR 503.

[102] Commonwealth Places (Application of Laws) Act 1970 (Cth) ss 3, 14.

[103] Cameron (n 21) 353–4 [47].

[104] See Stellios, Federal Judicature (n 38) ch 4.

[105] Markarian v The Queen (2005) 228 CLR 357, 371 [25]–[27] (Gleeson CJ, Gummow, Hayne and Callinan JJ).

[106] Street v Queensland Bar Association [1989] HCA 53; (1989) 168 CLR 461, 571–3 (Gaudron J); Simpson, ‘The High Court’s Conception of Discrimination’ (n 30) 267–8.

[107] Stellios, Zines’s The High Court (n 24) 309.

[108] Ananian-Welsh (n 73) 175.

[109] Stellios, Zines’s The High Court (n 24) 651–3; Leslie Zines and GJ Lindell, ‘Form and Substance: ‘Discrimination’ in Modern Constitutional Law’ [1992] FedLawRw 5; (1992) 21 Federal Law Review 136.

[110] Leeth (n 2) 493.

[111] Ibid; Christine Parker, ‘Protection of Judicial Process as an Implied Constitutional Guarantee’ [1994] AdelLawRw 13; (1994) 16 Adelaide Law Review 341, 351.

[112] Simpson, ‘Equal Treatment’ (n 60) 200.

[113] Ibid 210.

[114] [2001] HCA 64; (2001) 207 CLR 584, 608.

[115] Austin v Commonwealth (2003) 215 CLR 185, 247 [118] (Gaudron, Gummow and Hayne JJ) (footnotes omitted) (emphasis added).

[116] Gaudron J also considered whether the discrimination could ‘reasonably be viewed as appropriate and adapted’ to that purpose: Leeth (n 2) 500.

[117] Cameron (n 21) 343–4 [15].

[118] (1990) 169 CLR 436.

[119] Ibid 343 [11].

[120] Leeth (n 2) 470 (Brennan J).

[121] Ibid 471 (Mason CJ, Dawson and McHugh JJ), 476 (Brennan J).

[122] Ibid 480 (Brennan J).

[123] Ibid 476 (Brennan J); Stellios, Federal Judiciature (n 38) 351 [6.72].

[124] Dixon, ‘The Functional Constitution’ (n 78) 464.

[125] See Stellios, ‘Centralisation of Judicial Power’ (n 92) 358–9, 372–3, 384; Brendan Lim, ‘Laboratory Federalism and the Kable Principle’ (2014) 42 Federal Law Review 519, 520.

[126] Cameron (n 21) 367–9 [88]–[95]; Putland (n 18) 212–13 [111]–[114].

[127] See Dixon, ‘The Functional Constitution’ (n 78) 487.

[128] R v Gee (2003) 212 CLR 230, 241 [7] (Gleeson CJ), 254–5 [63] (McHugh and Gummow JJ), 269–70 [115]–[116] (Kirby J), 285 [180] (Callinan J).

[129] Ibid 241 [7].

[130] Commonwealth Director of Public Prosecutions, ‘Sentencing of Federal Offenders in Australia: a Guide for Practitioners –Fourth Edition’ (Guide, 25 February 2021) [1073]–[1084] <>.

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