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Yossi Nehushtan: The Unreasonable Perception of Rationality and Reasonableness in UK Public Law

In the recent case of R (Campaign Against Arms Trade) v Secretary of State for International Trade [2019] (hereinafter CAAT), the Court of Appeal invalidated the UK government’s decision to grant licences for the sale of military equipment to Saudi Arabia for possible use in the conflict in Yemen. The court found that the government had violated Article 2.2 of the EU Common Council Position 2008/944/CGSP, as adopted in the Secretary of State’s 2014 Guidance. Article 2.2 compels Member States to deny a licence for the sale of military equipment to other states if there is a clear risk that this equipment might be used ‘in the commission of serious violations of international humanitarian law’.

In 2015 a coalition of nine states led by Saudi Arabia commenced military operations against the Houthis in Yemen. The court in CAAT held that the question of whether there was a historic pattern of breaches of international humanitarian law on the part of the coalition – and Saudi Arabia in particular – was central to the estimation of the risk of future violations. The ‘historic pattern question’, however, was not addressed by the UK Government. That, according to the court, made the decision-making process irrational and therefore illegal. The court invalidated the granting of the licenses – but allowed the Secretary of State to reconsider his decision, by taking into account the historic pattern of breaches of international humanitarian law on the part of the coalition.

This case gives rise to interesting questions about justiciability, judicial deference and the scope of judicial review. Here, however, I wish to focus on the confusing yet common way in which the court used ‘rationality’ as ground of judicial review.

Rationality is a well-established ground of judicial review in UK public law. At the same time, the meaning of ‘rationality’ as ground of review is far from clear. Currently in UK public law, rationality review is understood in the following ways:

(1) Rationality as indistinguishable from reasonableness. It is quite common in UK public law to use the terms ‘reasonableness review’ (or Wednesbury reasonableness) and ‘rationality review’ (or Wednesbury rationality) indistinguishably, yet without always explaining the exact meaning of these grounds of review. It was probably the influential view of Lord Diplock’s in the GCHQ case (1984) that made the most significant contribution to enshrining the conceptual mistake of seeing reasonableness and rationality as indistinguishable. This was done by classifying the grounds of judicial review to three main categories: ‘illegality’, ‘irrationality’ and ‘procedural impropriety’; and by clarifying that ‘irrationality’ is in fact identical to ‘Wednesbury unreasonableness’.

(2) Rationality as a distinct ground of review that, compared to reasonableness, sets a lower hurdle for the administrative body. This approach, albeit within a specific context, was taken by the Supreme Court’s in its decision in Evans (2015), according to which a demand to base a decision on ‘reasonable grounds’ sets a higher hurdle than ‘mere rationality’ (paras 91, 129).

(3) Rationality as a ground of review that focuses on the decision-maker’s ‘mental process’ as opposed to reasonableness review that focuses on the outcome – i.e. the decision-maker’s decision. See for example Lord Sumption’s view in Hayes (2013) that ‘reasonableness is an external, objective standard applied to the outcome of a person’s thoughts or intentions… A test of rationality, by comparison, applies a minimum objective standard to the relevant person’s mental processes’ (para 14).

(4) Rationality as a mega ground of judicial review that covers more specific grounds of review such as acting in bad faith, acting capriciously or arbitrarily etc. For this view see also in Hayes, where Lord Sumption held that ‘a test of rationality… imports a requirement of good faith, a requirement that there should be some logical connection between the evidence and the ostensible reasons for the decision, and (which will usually amount to the same thing) an absence of arbitrariness, of capriciousness or of reasoning so outrageous in its defiance of logic as to be perverse’ (Hayes para 14).

(5) Rationality as fairness, consistency or equality. This approach was taken in Gallaher (2018), especially by Lord Carnwath and Lord Sumption who asserted that it is irrational to treat like cases differently – if there is no ‘objective justification’ for the different treatment {paras 27, 43, 44, 55 (Lord Carnwath) and para 55 (Lord Sumption)}.

(6) ‘Instrumental rationality’ that requires logical or causal relation between means and end. Instrumental rationality is in fact part of the principle of proportionality. It is common to refer to the principle of proportionality as a four-stage test which includes legitimate aim; suitability (or rational connection); necessity (or applying the least intrusive measure); and proportionality in the narrow sense (proportionality stricto sensu). When we apply the second stage that sets the suitability or rationality test we are asking whether the means (that is, interfering with a protected right or interest) can achieve the legitimate aim of the law or of the administrative decision. If there is no rational connection of any kind between the means and the end, that is, if the means cannot or does not achieve the end, then this is a decision that no rational person could have made.

In the recent CAAT case, rationality review was applied in a rather confusing way. At the core of its reasoning, the court equated rationality with the duty to take into account all relevant considerations. In other places in the judgment rationality was also equated with reasonableness. The court repeatedly held that it was irrational to not take into account the historic pattern of breaches of international humanitarian law on the part of the coalition while making the decision about granting the licenses (paras 35, 57-59, 62, 139, 144, 145, 153). The court relied on Tameside (1977) that established the proposition that a public body has a duty to carry out a sufficient inquiry prior to making its decision. The court emphasised that ‘the only legal error which is alleged to have been committed is founded on the public law doctrine of irrationality’ and that rationality refers to the decision-making process, and in our case – the duty to take into account all relevant considerations (para 57).

The problem is that not taking all relevant considerations into account is a distinct, well-established ground of judicial review in public law. Equating this ground of review with ‘rationality’ adds nothing to our understanding of that ground of review. It also means that rationality review has no distinct meaning in UK public law. The court then continued to assert that ‘what must be shown by CAAT is that the process which was adopted by the Secretary of State was one which was not reasonably open to him’ (para 57), thus equating rationality with reasonableness – and equating both with the duty to take into account all relevant consideration. A similar approach was taken by the Supreme Court in the Braganza case of 2015, by concluding that the decision that was scrutinized by the court was ‘unreasonable in the Wednesbury sense, having been formed without taking relevant matters into account’ (para 42, and see also paras 53 and 103).

With respect, arguing that it is unreasonable or irrational to not take all relevant considerations into account is conceptually confusing and in fact misguided. It is not more helpful than arguing that it is unreasonable or irrational to take irrelevant considerations into account, act in bad faith, be in a state of conflict of interests, act for an improper purpose etc. Describing distinct grounds of review by attaching the concepts ‘unreasonable’ or ‘irrational’ to them adds nothing to our understanding of these distinct grounds of review – and makes reasonableness and rationality mega-grounds of review with no distinct meaning. It is both surprising and unfortunate that conceptual mistakes that were made more than 70 years ago in Wednesbury – and 35 years ago in GCHQ – still inform current judicial decisions in UK public law. The GCHQ case, more specifically, collated almost all grounds of review that relate to the exercise of discretionary powers under the title ‘rationality’ – and continued to equate rationality with reasonableness, thus making the terms ‘rationality’ and ‘reasonableness’ redundant. But they are not. We should better describe what reasonableness review and rationality review are (as separate grounds of review) – and distinguish them from other, distinct grounds of review.

Reasonableness as a distinct ground of review can only be understood as a weighing and balancing test – one that refers to the content of the administrative decision rather than to the decision-making process. An unreasonable decision is one that results from according distorted weight to relevant considerations. Back in 1947, Lord Greene stated in the Wednesbury case that courts can scrutinize the reasonableness of an administrative decision only after establishing that the decision was intra vires; that the decision-making process was intact; that all the relevant considerations were taken into account; and that irrelevant considerations were not taken into account – or that the administrative body did not try to achieve improper purpose. Lord Greene failed to reach the inevitable conclusion: that after taking into account all relevant considerations and nothing but relevant considerations, the only thing that can go wrong with regard to the legality of the administrative decision is the weight accorded to the relevant considerations. Therefore, for reasonableness to have any distinct meaning in public law it must only refer to the weight that was accorded to the relevant considerations – and not to the relevancy of these considerations.

Rationality as a distinct ground of review can only be understood as ‘instrumental rationality’. This is perhaps the most common perception of rationality. It is often applied in the legal world and especially in public law – as part of the proportionality test. It describes rationality as deploying the appropriate means in order to achieve certain ends (whatever these ends may be). After years of applying the proportionality test in UK public law (in cases involving the ECHR or EU law) we now know what the rationality test means within the context of public law. Perceiving rationality as ground of review that focuses on the relation between means and end is the most helpful and accurate way to understand the distinctiveness of this ground of review. This perception of rationality is sufficiently specific – but not too narrow. It avoids vagueness and uncertainties. It does not apply to cases that are better described and scrutinised by other grounds of review. It is the only concept, together with ‘suitability’, that describes the necessity to have some relation between means and end – and it is already being applied in that way within the framework of proportionality review. All that we need to do is to apply this concept in the same way, clearly and consistently, also outside the context of proportionality review – and outside the context of protected rights.

The perception of rationality review as ‘instrumental rationality’ also explains why it is confusing and misleading to equate rationality with reasonableness, as only the latter is a balancing test. We should acknowledge that we have in UK public law two completely different grounds of judicial review: rationality and reasonableness. The only similarity between the two is that they allow the court to scrutinize the content of the administrative decision. But this is where the similarity ends as the nature of these ground of review, the requirements that they set for the administrative body and the levels of scrutiny they allow the court to apply are completely different.

Back to the CAAT case: the UK government did fail to take into account a relevant consideration. Labelling this failure as irrational or unreasonable is unnecessary, confusing and in fact misguided. The decision to grant licences could have been unreasonable only if the government took into account all relevant considerations but accorded them distorted weight. That was not the case in CAAT. The decision to grant licences could have been irrational only if the means (granting licences) had no causal or logical connection to the Government’s end (whatever that end might be). This question, however, was not discussed in CAAT.

The CAAT case does give rise to important normative questions about the proper scope and intensity of judicial review in UK public law, but these questions cannot be answered before we lay out a common ground with regard to the meaning of the grounds of judicial review – and especially the currently most ambiguous ones: reasonableness and rationality.

My thanks are due to Stephen Tierney and Luke Griffiths for commenting on the first draft of this post.

Yossi Nehushtan, Senior Lecturer, School of Law, Keele University

(Suggested citation: Y. Nehushtan, ‘The Unreasonable Perception of Rationality and Reasonableness in UK Public Law’, U.K. Const. L. Blog (available at (1st Jul. 2019))

4 comments on “Yossi Nehushtan: The Unreasonable Perception of Rationality and Reasonableness in UK Public Law

  1. sjasloan
    July 1, 2019

    You will know more about this than me. My random thoughts:

    Surely a decisionmaker failing to consider a relevant consideration has simply committed a decision making mistake? Which should be corrected. But not unreasonable, The decision* process *was defective

    Saying an admin decision is unreasonable on whatever basis is simply and impermissibly stepping into the decision maker’s shoes.

    And rationality is all about means and ends!!!!??? If the ends – the admin decision – is *outside power* then the decision must be unlawful and void? Else what is it?

    UK administrative law seems to be a circuitous mess.


    • Yossi Nehushtan
      July 2, 2019

      Thank you Steve.
      Failing to consider a relevant consideration is indeed ‘a decision-making mistake’ and may result in invalidating the decision. But the decision should not be classified as unreasonable.
      Saying that an administrative decision is unreasonable ‘on whatever reason’ is not the same as stepping into the decision-maker’s shoes. I’m not sure what ‘on whatever reason’ means. If it means a reason that falls within the scope of a different, distinct ground of review, then using the term ‘unreasonable’ would be wrong but it will not be ‘stepping into the decision-maker’s shoes’. If reasonableness is applied in the way I suggested in the post, it does set limits to the administrative body’s discretion – but not necessarily in a way that puts the court in the decision-maker’s shoes.
      Yes, rationality is or should be ‘all about means and end’. If the end is ‘outside power’ that would be acting ultra-vires or acting for an improper purpose. It may make the administrative decision illegal – but not necessarily irrational.
      I hope my post and response made administrative law a bit less messy.

  2. rhysdelahay
    July 1, 2019

    One of the most infuriating statements in Public law for me was the ignorance and denial of the sender’s of terrorist footage, Recipients of illegal footage on-line were told by the TM Government to delete it. It is wrong to delete evidence big criminal activity as we all know, and ignorance is no excuse for negligence especially in Criminal law. The receipt of scam and terrorist videos should have been reported and traced back to the source.

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  3. robin-mcburnie
    July 15, 2019

    As someone who absolutely hates “The Law” as it stands, I find this sort of messiness frustrating. I’m used to electronics and software, so I understand the problem of complexity and wouldn’t expect the Law to be simplistic.

    I do however believe that a lot could be learned from the likes of the W3C who manage to set the standards by which the Internet and most associated protocols work in a structured way that works well. Bearing in mind that it has to balance requirements from more companies, developers, users, telecomms networks (local, national and international) and other parties than your average UK law.

    Specific to your post, clear and precise definitions of the meaning and context of absolutely ALL key terms used are agreed and published. Thus it is not down to the “interpretation” of any individual developer, company or even nation.

    Clarity and structure along with openness and consultation are the key elements.

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