Marcus Teo: Rationality Review in Singapore: Authority, Expertise and Legality

Judicial review is a matter of justification: depending on how courts justify it, they may reach very different conclusions about the proper ambit of their powers. This is particularly felt in relation to judicial review on grounds of Wednesbury unreasonableness or “rationality review” where, given the closeness of the inquiry to a decision’s merits, the question of the court’s legitimate role in relation to executive decision-making comes into sharp relief.

There are at least three different justifications for rationality review, which may lead to three different conclusions about its legitimate ambit. First, rationality review may be justified on the basis of the court’s constitutional authority. The issue then is: which decision-makers are subject to the court’s supervision, and which are beyond it, by virtue of their own authority? Second, rationality review may be justified on the basis of the court’s subject-matter expertise. The issue then is: which fields of decision-making should the court review, and which should it not, given its capacity to understand matters therein? Third, rationality review may be justified on the basis of the court’s duty to uphold legality. The issue then is: what does the “rule of law” demand in this particular case?

Singapore’s courts have grappled with these three justifications for rationality review at different points in time. Most recently, they have been of the opinion that neither a decision-maker’s authority, nor a decision-making field’s subject-matter, should determine the ambit of rationality review “ which is, instead, strictly a question of legality: courts are simply called to do what the “rule of law” requires. This post traces these developments on how rationality review is justified in Singapore law, focusing on one of the most contentious executive decision-making powers therein: the prosecutorial power. It notes that these developments mirrors similar developments in English law, but also questions how a reliance on its current justification for rationality review may be reconciled with Singapore’s constitutional culture.


English courts, up till the mid-20th century, were not confident that they had the authority to exercise rationality review over the decisions of certain constitutional actors. Specifically, English courts were reluctant to assert jurisdiction over the Royal prerogative, and hence also hesitant to exercise rationality review over executive decision-makers who were delegated aspects thereof, such as officers of the foreign service. Thus, a decision-maker’s authority within the English constitutional system – specifically, how closely her authority was affiliated with the Crown – determined the extent to which her decisions were subject to rationality review.

In Singapore, this same justification of authority (i.e. of the nature and rank of the decision-maker’s office, vis a vis the court’s) was also once used to determine the extent to which the prosecutorial power could be subject to rationality review. In Law Society of Singapore v Tan Guat Neo Phyllis (2007), Singapore’s High Court held that exercises of prosecutorial power could be reviewed if exercised in “bad faith for an extraneous purpose”, but not on grounds of rationality review. The Court noted that this had to be so “given that [the prosecutorial power] is a constitutional power” (emphasis added). Subsequently, in Ramalingam Ravinthran v Attorney-General (2012), the Court of Appeal held that the prosecutorial power was shielded by a presumption of constitutionality, “consistent with the constitutional standing of the office of Attorney-General” (emphasis added). But the court’s authority (or lack thereof) would not define rationality review for long: changing conceptions of the separation of powers doctrine in both England and Singapore saw courts leaning away from authority, and toward subject-matter expertise, as the basis for rationality review.


English law’s transition to expertise-based rationality review occurred in the GCHQ case (1984), where the House of Lords held that the ambit of rationality review should “depend upon the subject matter of the [decision-making] power which is exercised”, and whether or not the court had the expertise to comprehend it. Thus, while certain exercises of Royal prerogatives could still be non-justiciable, this was so not because of who they were wielded by (e.g. the foreign service), but because their subject-matter was not “amenable to the judicial process”. This, what Murray Hunt calls a “spatial” approach to rationality review, was subsequently affirmed by the House of Lords in R v DPP, ex parte Kebilene (2000), where Lord Hope recognised that there were “area[s] of judgment within which the judiciary will defer”.

In Singapore, the same justificatory shift from authority to subject-matter expertise, would occur as well. In Tan Seet Eng v Attorney-General (2015), Singapore’s Court of Appeal held that the decisions of no “administrative authority” were absolutely immune from judicial review, but also that “the more remote the subject matter of a decision from ordinary judicial experience, the more hesitant the court must necessarily be in holding a decision to be irrational” (emphasis added). This expertise-based approach was then applied to the prosecutorial power in the Singapore High Court’s decision in Nagaenthran a/l K Dharmalingam v Attorney-General (2018). There, a statutory provision that appeared to oust (only) rationality review over certain exercises of the prosecutorial power related to the disruption of drug trafficking activities was upheld as constitutional. The Court held that such exercises of the prosecutorial power were “clearly non-justiciable”, since courts were institutionally “ill-equipped” to understand “the operational considerations of the [police] in the disruption of drug trafficking activities” and that conversely, the Public Prosecutor “possess[ed] the unique qualities” necessary to understand such considerations. The implication, therefore, was that those exercises of prosecutorial power were immune from rationality review because the subject-matter of those decisions involved the police’s “operational considerations”.


In the past decade, English courts appear to have lost faith in either authority or subject-matter expertise as the lodestar for determining the ambit of rationality review. Instead, they have begun to take what might be termed a “legality” approach to rationality review: the question, simply put, is whether and to what extent the “rule of law” demands rationality review. Most recently, in R v International Privacy Tribunal (2019), a majority of the UK Supreme Court held that the question of whether and to what extent a decision should be subject to judicial review required a “balanced assessment” of the issue in question, in particular whether it may “properly and economically” be left to the executive to determine. In the words of Lord Carnwath, “[t]he question in any case is…what scope of judicial review…is required to maintain the rule of law”.

In Singapore, the High Court’s decision in Nagaenthran had gone on appeal. Mere days after the UK Supreme Court decided International Privacy Tribunal, Singapore’s Court of Appeal issued its decision inNagaenthran a/l K Dharmalingam v Attorney-General (2019). There, it held that judicial review, including rationality review, formed the “core” of the judicial power under Article 93 and was essential to the “rule of law”. The Court drastically read down the aforementioned statutory provision which apparently ousted rationality review over certain exercises of the prosecutorial power, finding that it was not an ouster clause at all, and that therefore nothing shielded the prosecutorial power from rationality review. Importantly, the Court also noted obiter that, had that provision actually purported to oust rationality review, it would have amounted to an unconstitutional infringement of the judicial power and the “rule of law”.

With its Court of Appeal’s decision in Nagaenthran, Singapore law appears to have settled on the same justificatory basis for rationality review that English law uses today: the court’s power of rationality review is not justified on its authority to supervise a decision or subject-matter expertise to understand a decision, which the court may sometimes lack, but on the demands of legality and the “rule of law”, which the court must always enforce.

Yet, whatever merits this justification for rationality review may have, it comes at the expense of theoretical defensibility, at least in Singapore’s constitutional context. To justify something on the “rule of law” is, to a large extent, question-begging: as Jaclyn Neo has argued, simply justifying judicial review on the “rule of law” and “saying that all power has legal limits does not tell us specifically what those limits are”. So, what exactly about “legality” or the “rule of law” tells us whether and to what extent rationality review should be asserted in Singapore? One may argue, as Sir John Laws did, that rationality review flows from “a particular view of the rule of law, in relation to public bodies, ultimately rooted in the Kantian notion of every individual’s equal autonomy”. However, such liberal “rule of law”-based justifications for rationality review are heavily influenced by England’s constitutional culture. It remains a real question whether and to what extent the “rule of law” should require rationality review in constitutional systems like Singapore’s, which, as Thio Li-Ann notes, may embrace an illiberal or communitarian constitutional culture instead. So even if Singapore’s courts do justify rationality review on the basis of “legality” today, why that should be so, and what exactly that entails, remain open questions.

Marcus Teo is a Teaching Assistant at the Faculty of Law, National University of Singapore.