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Singapore’s dual approach to the reasonable classification test

Updated: 6 days ago

By Sit Jie Ren


The right to equality before the law and equal protection of the law is one of the key constitutional liberties enshrined in Article 12 of the Constitution of Singapore.[1] The orthodox approach taken by Singapore’s courts, when assessing the constitutionality of statutory provisions and executive actions under this Article, has been the reasonable classification test as outlined by Taw Cheng Kong[2] and Lim Meng Suang,[3] which functions as a test of formal equality. However, in recent years, a separate approach has emerged in Syed Suhail[4] for executive actions. This article will briefly outline both approaches and highlight key differences between the two, before advocating for the adoption of the Syed Suhail approach as the new orthodoxy in Singapore’s courts.[5]


Article 12 of the Constitution of Singapore

Equality before the law is one of the fundamental principles under Raz’s formal conception of the rule of law. Unsurprisingly, multiple commonwealth jurisdictions have included it as a constitutionally protected right, including South Africa[6], India[7] and Malaysia.[8] This principle is protected under Article 12 of Singapore’s Constitution, which comprises two main parts:


(1)   All persons are equal before the law and entitled to the equal protection of the law.

(2)   Except as expressly authorised by this Constitution, there shall be no discrimination against citizens of Singapore on the ground only of religion, race, descent or place of birth in any law or in the appointment to any office or employment under a public authority or in the administration of any law relating to the acquisition, holding or disposition of property or the establishing or carrying on of any trade, business, profession, vocation or employment.


The first, Article 12(1), is worded more generally as a declaratory statement of principles,[9] and applies to all individuals within Singapore’s jurisdiction. On the contrary, Article 12(2) applies only to citizens of Singapore and prohibits discrimination solely on certain specific grounds.[10]


The Court of Appeal in Lim Meng Suang noted that Article 12(1) can be further separated into two limbs, the first being that “[a]ll persons are equal before the law” and the second being that “all persons are…entitled to the equal protection of the law”, which the court found to be a declaratory statement of principles that does not espouse any specific legal criteria to guide Singapore’s courts in determining the constitutionality of statutes or executive actions under Article 12.[11] Hence, Singapore’s courts have developed the reasonable classification test to assess the constitutionality of statutes and executive actions under Article 12. However, in recent years, two distinct approaches to this test have emerged.


The Taw Cheng Kong approach

The orthodox approach to the reasonable classification test was first adopted by the Court of Appeal in deciding the seminal case of Taw Cheng Kong,[12] largely based on Mohamed Azmi SCJ’s test in Malaysian Bar v Government of Malaysia.[13]  In Taw Cheng Kong, the appellant sought to challenge the constitutionality of s 37 of the Prevention of Corruption Act,[14] which criminalised corrupt acts by a citizen of Singapore outside of Singapore. The test was later affirmed and clarified in Lim Meng Suang, which concerned the constitutionality of the now repealed s 377A of the Penal Code. Under the approach in Taw Cheng Kong and Lim Meng Suang, the test has two limbs, where a statute is consistent with Article 12(1) only if:[15]


(a)   the classification prescribed by the provision is founded on an intelligible differentia; (the “intelligible differentia limb”)

(b)   that differentia bears a rational relation to the object sought to be achieved by the provision. (the “rational nexus limb”)


Under the intelligible differentia limb, the courts identify the basis of differential treatment between individuals under the statutory provision, and assess whether this basis is ‘intelligible’. Here, the intelligibility of the differentia is assessed by reference to whether it “is capable of being apprehended by the intellect or understanding”.[16] However, a differentia could still fail this limb if it were extremely unreasonable “as to be illogical and/or incoherent”,[17] which requires the court to consider whether no reasonable person would consider the differentia “as being functional as [an] intelligible differentia”. Importantly, the Court of Appeal highlighted that the requirement for a classification to be “intelligible” is a low threshold that excludes the consideration of any “substantive moral, political and/or ethical issues”[18], which appropriately belong under the remit of Parliament. Nevertheless, the limited test of legitimacy through unreasonableness has been criticised for bringing extra-legal, sociological considerations into judicial decision making.[19]


The rational nexus limb then compares the differentia identified from the first limb with the legislative object of the statutory provision and assesses if there is any rational nexus between them. The Court of Appeal held that there was no requirement for a “complete coincidence” between the two, only that the connection ought to be “rational” which was to be determined on the “specific facts” and “context” of the case.[20]


The Court of Appeal further held that a presumption of constitutionality would apply to statutory provisions challenged under Article 12, which the applicant had to rebut by adducing evidence to demonstrate the arbitrariness of the statute or decision.[21] The full burden of proof is placed on the applicant under this approach.


The Syed Suhail approach

Meanwhile, the Court of Appeal has espoused a different approach in the case of Syed Suhail, where the appellant challenged the scheduling of his execution before other death-row prisoners when his clemency petition had been declined after them. This case concerned an executive action whereas the previous approach was applied in cases concerning the constitutionality of statutory provisions.


The Syed Suhail approach has its origins in a prior Court of Appeal decision in Ridzuan, and has the following two limbs:[22]


(a)   whether the persons in question could be said to be equally situated such that any differential treatment required justification; and

(b)   whether the differential treatment was reasonable.


This approach differed from the former approach in three substantial ways, which was discussed by the court in Tan Seng Kee.[23] Firstly, the first limb of the Syed Suhail approach merely identifies the differential treatment and does not pass any normative judgement on its reasonableness.[24] Any provision with an unintelligible differentia would instead fail on the second limb for lacking a rational relation to “any conceivable legislative object of that law”.[25]


Secondly, the presumption of constitutionality is approached differently under the Syed Suhail approach. Unlike the previous approach, the presumption of constitutionality here merely requires the applicant to demonstrate that there has been a prima facie breach of the reasonable classification test, which could be done by proving that he was equally situated with another individual but yet was treated differently, or that there had been imperfect differentiation. There would then be a ‘shifting’ of the burden of proof to the government, requiring the government to rebut the applicant’s case by demonstrating the reasonableness or legitimacy of the differential treatment.[26] This contrasts with the Taw Cheng Kong approach which places the burden of proof solely on the applicant.


Lastly, the court held in Syed Suhail that courts would apply different levels of scrutiny in applying the reasonable classification test, which would pivot on whether the decision was taken in relation to individual cases or applied broadly, and whether the decision “affected the appellant’s life and liberty to the gravest degree”.[27]


The obiter in Tan Seng Kee

In Tan Seng Kee, a subsequent constitutional challenge to s 377A, Menon CJ, writing for the unanimous decision of the Court of Appeal, considered the differences between both approaches in obiter (as previously mentioned). Notably, the Syed Suhail approach was applied in a case challenging the constitutionality of statutory provisions when it had previously only been applied to cases involving executive actions,[28] setting the stage for its broader use in future cases.


Menon CJ also provided further guidance to courts on the application of the Syed Suhail approach in Tan Seng Kee in his dictum, stating that the purpose of a statute identified by courts cannot be stated as “[introducing] the differentia that it embodies” as that would entail circular reasoning, rendering the reasonable classification test otiose as “a perfect relation between the differentia and the object of [the] law” would always be found.[29] Menon CJ stressed the importance of “framing the object of a law…at the appropriate level of generality”[30] but did not provide much further guidance on this point.


The dictum did not express an explicit preference for either approach,[31] but Teo, Sheridan Fellow at the Faculty of Law, National University of Singapore, contends that the court appeared to lean heavily in favour of the Syed Suhail approach.[32]


The preferred approach

Nevertheless, the present constitutional position on Article 12 remains unsettled, with courts yet to definitively decide on which of the two approaches to adopt. However, the Syed Suhail approach should be preferred considering its lowered presumption of constitutionality, and its stricter form of scrutiny in protecting certain rights.


It is desirable that the presumption of constitutionality ought to be lowered when considering the constitutionality of legislative provisions and executive actions. As the court Lim Meng Suang highlighted, the reasonable classification test is insufficient in ensuring a basic level of equality in law, but merely functions as a threshold test in assessing if legislative provisions (and by extension executive actions) comply with Article 12.[33] Imposing a strong presumption of constitutionality in the manner conceived by the Taw Cheng Kong approach would impose an extremely high (if not impossible) evidential burden on the applicant, further reducing the efficacy of an already inadequate protection of constitutional rights (if not nullifying it). This is due to the difficulty of the applicant in acquiring a sufficiently comprehensive understanding of government operations as to adduce sufficient evidence to overcome the presumption.[34] The situation is worsened by the mere requirement for a rational relation between the legislative object and the differentia, which imports a fairly low threshold and further weighs the test in favour of the government. Indeed, Phang JA concedes as such in Lim Meng Suang, admitting that “the requisite rational relation will – more often than not – be found”[35], and there is no known constitutional challenge in Singapore which has succeeded in demonstrating the lack of a rational relation to date. This may have led Teo to suggest that the Court of Appeal developed the Syed Suhail approach to rescue the reasonable classification test from being impossible for applicants to succeed by modifying the presumption of constitutionality.[36] By only requiring the applicant to discharge their burden by raising a prima facie case of reasonable suspicion and instead requiring the government to demonstrate that the differential treatment was justified, the burden of proof that the differentia bears a rational relation to the legislative object is now more aptly placed with the government, which is better placed to explain the considerations behind its decision vis-a-vis the applicant.


Furthermore, the stricter scrutiny adopted by the Syed Suhail approach when approaching statutory provisions or executive actions which impinge on an individual’s “life and liberty” further militates in favour of its adoption. Under the Taw Cheng Kong approach, there does not appear to be any difference in the level of scrutiny when courts approach constitutional challenges to Article 12, regardless of the subject matter of the case. However, as mentioned previously, there is no requirement for a perfect relation between the differentia and the legislative object under the reasonable classification test, only that the relation be “rational”. Clearly, it would be inappropriate for the degree of rationality expected to be the same where the subject matter of the statute or decision concerns more ordinary matters as opposed to ones which concern more fundamental rights, considering the greater need and importance for courts to safeguard the latter. Teo suggests that this could be done by adopting different approaches towards imperfect differentiation, whereby such imperfection can ordinarily be explained through the mere presence of practical constraints,[37] but courts will be entitled to assess the normative sufficiency of such practical reasons where fundamental liberties were at stake.[38] Adopting Teo’s approach, this seems to provide the necessary flexibility for the government to act or legislate in ordinary circumstances where practical considerations mean that some degree of ‘unfairness’ in differentiation will necessarily occur, and at the same time, enables the test to meaningfully protect the constitutional liberties of individuals by limiting the government’s ability to rely on mere inconvenience as justification for impinging on these important rights and liberties. Here, Teo contrasts the cases of Howe Yoon Chong,[39] where imperfect differentiation between property owners was justified due to the difficulty and impracticability of the Chief Assessor updating the valuation of every property annually when drawing up annual valuation lists for the purpose of property tax, and Syed Suhail, which concerns the rights of a death-row prisoner facing imminent execution, to demonstrate the inappropriateness of imperfect differentiation being justified on the basis of limited resources.[40] This demonstrates the desirability, if not necessity, of courts adopting differing levels of scrutiny in applying the reasonable classification test. Considering this, the Syed Suhail approach seems to accord a more adequate protection of constitutional rights compared to the Taw Cheng Kong approach.



In conclusion, the Syed Suhail approach is an evolution of the reasonable classification test towards a more rights-based approach which provides applicants with a more realistic chance of succeeding in an Article 12 judicial review case. Nevertheless, as Teo’s article evinces, the existing case law leaves many questions unanswered and Singapore’s courts have yet to fully develop the reasonable classification test.[41] At this point, it bears mentioning that the Constitution of Singapore is relatively new and the development of the jurisprudence surrounding it is still nascent. We can expect much greater clarity on the application of the reasonable classification test from the Court of Appeal in the coming years and decades as more cases on Article 12 are decided.


[1] Constitution of the Republic of Singapore, Art 12

[2] Public Prosecutor v Taw Cheng Kong [1998] SGCA 37 (“Taw Cheng Kong”)

[3] Lim Meng Suang v Attorney-General [2014] SGCA 53 (“Lim Meng Suang”)

[4] Syed Suhail v Attorney-General [2020] SGCA 122 (“Syed Suhail”)

[5] Due to limitations in scope, this article will not address the ongoing academic debate on whether a test of substantive equality should be introduced, or the possibility raised in Tan Seng Kee by Menon CJ on whether a different approaches ought to be taken when assessing statutory provisions and executive actions (see Tan Seng Kee at [328]), but will merely seek to compare the two existing approaches to the reasonable classification test.

[6] Constitution of South Africa, ch 2, s 9

[7] Constitution of India, Art 14

[8] Constitution of Malaysia, Art 8

[9] Lim Meng Suang [73]-[74].

[10] Ibid [90]-[94].

[11] Ibid [73]-[74].

[12] Taw Cheng Kong [57]-[59].

[13] [1987] 2 MLJ 165.

[14] Prevention of Corruption Act 1960, s 37

[15] Lim Meng Suang [60].

[16] Ibid [67].

[17] Ibid.

[18] Ibid [65].

[19] Marcus Teo, ‘Refining Reasonable Classification’ [2023] SJLS 83, 92

[20] Ibid [68].

[21] Taw Cheng Kong [80].

[22] Syed Suhail [62].

[23] Tan Seng Kee v Attorney-General [2022] SGCA 16 (“Tan Seng Kee”)

[24] Ibid [318].

[25] Ibid [318]-[319].

[26] Syed Suhail [61].

[27] Ibid [63].

[28] Tan Seng Kee [313]-[328].

[29] Tan Seng Kee [320].

[30] Ibid.

[31] Tan Seng Kee [329].

[32] Ibid, 91

[33] Lim Meng Suang [61]-[62].

[34] Teo highlights that there exists an “information asymmetry” between applicants and the Government which works in favour of the Government in his article at p 106.

[35] Ibid [68].

[36] Ibid, 105

[37] Ibid, 100

[38] Ibid, 102-103

[39] Howe Yoon Chong v Chief Assessor [1990] 1 SLR(R) 78

[40] Ibid, 103

[41] Ibid, 92-97, 103-105, 106-109

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