A. Institutional and legal contexts

The following two sections shed more light on how EU adjudication engages with complex and uncertain scientific appraisals. They analyse the likelihood that, in the specific institutional setting of the EU Courts and the ECHA BoA, the adjudicators independently evaluate the probative value of complex and uncertain evidence and the soundness of specialist reasoning.

The institutional setting of EU Courts does not seem strongly conducive to judges’ acquiring specialist knowledge, especially tacit, necessary to develop ‘scientific connoisseurship’. First, due to their generalist composition, the empirical evaluations by the EU Courts seem to be informed more by ubiquitous than specialist tacit knowledge. There is no fully-fledged specialisation of EU judges and their supporting staff in specific policy areas.^{Footnote 64} This limitation stems from the EU’s political and constitutional structure. Introducing specialisation would necessarily involve creating judicial portfolios (in competition law, risk regulation, civil service law, etc.) distributed among the Member States, which nominate candidates to the EU judicial posts. The existence of such judicial portfolios could lead to political disputes, complicating judicial appointments. Specialisation may also result in an emergence of narrow epistemic communities within the courts, with concomitant risks for the uniformity of case law across different policy fields.

Second, the reasoning of EU Courts and the intensity of judicial review in most types of proceedings is conditioned by the arguments, evidence and its elucidation provided by the parties (usually in a written form),^{Footnote 65} no matter how intense the standard of judicial review is officially proclaimed. In such an essentially adversarial setting,^{Footnote 66} the applicants specify the subject matter of proceedings (the contested act, the pleas in law) and carry the burden of persuading the EU judges that the contested act is vitiated by a breach of law, including a violation of the duty of care or a manifest error of assessment.^{Footnote 67} If the parties, or rather their lawyers, fail to advance appropriate pleas in law or fail to substantiate them, it may be that an objectively faulty or unlawful EU measure will remain in force.^{Footnote 68}

Third, the EU Courts do not engage in independent fact-finding, including by appointing independent experts or organizing a hearing of partisan experts,^{Footnote 69} although the rules of procedure allow for such procedural measures.^{Footnote 70} At oral hearings, the judges interact with lawyers only.^{Footnote 71} This procedural setting fosters an efficient use of judicial resources and a reasonable duration of proceedings. It also safeguards the decision-making autonomy of the challenged EU institutions and bodies. It prevents the EU Courts from ‘taking over’ the primary responsibility for decision-making.Footnote ⁷² Moreover, allowing partisan or court-appointed experts to appear in the courtroom could generate an infinite regress. How would generalist judges assess subsequent substantive allegations against the expert testimony? By appointing further experts?

Apart from this institutional and procedural setting, one should also keep in mind the characteristics of the applicable EU substantive legal frameworks. These frameworks lay down conditions where EU institutions and bodies may undertake regulatory action, providing indications regarding this action’s contents as well. However, they do so utilising under-determined concepts, the interpretation of which requires reaching out to specialist knowledge such as a ‘risk to human health or the environment’^{Footnote 73} or ‘active substance’.^{Footnote 74} Such legal concepts bind and orient the exercise of technical and political discretion only to a relatively limited extent.^{Footnote 75} This little ‘steering capacity’^{Footnote 76} of EU substantive law is why specialist appraisals constitute a significant challenge for law-based adjudication. Rather than only applying clear-cut substantive legal criteria, EU adjudicators must also verify whether the contested empirical appraisals are ‘objectively’ plausible or even correct.

Last but not least, the precautionary principle should be kept in mind. It is a general principle allowing regulatory action to address uncertain risks even if conclusive evidence of these risks is unavailable, which is often the case in regulatory science.^{Footnote 77} This principle is seen as a crucial legal tool enabling decision-makers and the courts to reach decisions, including on regulatory action addressing hazards and risks despite scientific uncertainty. Undoubtedly, it has an intuitive appeal. Some proponents of this principle suggest that judicial review should not even aim at setting out minimum threshold conditions for when this principle can be triggered. In this view, judicial review should only concern itself with whether the impugned regulatory action has been based on any scientifically verified proposition.^{Footnote 78} Why should courts apply such self-restraint? They may have a ‘natural’ propensity towards searching for ‘hard evidence’, rooted in one of the central tenets of the liberal rule of law. According to this tenet, individual freedom of action (and business) may be restrained only when that course of action proves clearly and undoubtedly necessary to protect other normative goals, following the principle of proportionality. Therefore, a snowball effect could be expected to follow. In the long run, courts would require increasingly conclusive evidence of hazards and risks, undermining the precautionary approach.

However, some scholars have pointed out the many difficulties inherent in the precautionary principle. Precautionary reasoning tends to focus on worst-case scenarios, ignoring that the probability of some risks is low. Hence, it may lead to a loss of potential gains from innovation. Preventing some risks may also lead to the emergence or re-emergence of others. Therefore, an overly precautionary approach may also lead to arbitrariness by providing normative support to regulatory action that would address purely hypothetical risks or lead to other adverse consequences.^{Footnote 79} For this reason, as argued, the precautionary principle cannot be a blank check to undertake ‘risk management’ measures addressing purely hypothetical, theoretical and unproven risks.^{Footnote 80} Even proponents of the precautionary approach could concede that only the risks underpinned by some ‘solid’, ‘convincing’ or ‘reasonable’ empirical basis can justify a regulatory response,^{Footnote 81} which implies that some minimum threshold conditions must unavoidably exist and, arguably, be amenable to judicial review. However, the problem lies in scientific uncertainty. Assessing where the minimum threshold lies may involve considerable technical and political discretion and require the epistemic capacity to distinguish between plausible and implausible scientific assessments.

B. Still catalysts

The above institutional, procedural, and legal context conditions how EU adjudicators engage with complex and uncertain specialist appraisals. This context should be kept in mind while analysing court rulings with an eye to understanding the intensity of review and evaluating whether the court could have been realistically expected to do more.

In some cases, specific pleas in law raised against contested EU legal acts and relating to the underlying specialist opinions make it possible for the EU Courts to eschew delving deep into the substance of these opinions. Instead, the courts focus on ensuring that the impugned regulatory or administrative action is indeed underpinned by adequate empirical evidence provided that the parties offer relevant pieces of evidence and its persuasive elucidation. In such cases, the EU Courts can still play the role of ‘catalysts’, to some extent, by ensuring that regulatory action is underpinned by adequate scientific assessment.

For instance, a recent case concerned the authorisation of specific uses of chromium trioxide under the ‘REACH’ Regulation.^{Footnote 82} The Commission can authorise the use of substances ‘of very high concern’, such as chromium trioxide, based on the opinions of the ECHA’s specialist Committees for Risk Assessment (RAC) and Socio-economic Analysis (SEAC). The legal conditions are that either ‘the risk to human health or the environment from the use of a substance arising from the intrinsic properties [of this substance] is adequately controlled’ or ‘it is shown that socio-economic benefits outweigh the risk to human health or the environment arising from the use of the substance and … there are no suitable alternative substances or technologies’.^{Footnote 83} Although REACH lists factors that should be considered,^{Footnote 84} analysing whether the legal conditions are fulfilled is characterised by considerable discretion delegated to RAC and SEAC and then to the Commission.

In this case, the Commission considered that the risk to human health of the proposed uses of chromium trioxide was not adequately controlled, but it authorised this substance nonetheless, holding that socio-economic benefits outweighed the risks. However, the Parliament relied on the opinions of ECHA committees to argue that the company applying for the authorisation had provided unrepresentative and unreliable data regarding the risks. In the Parliament’s view, logically, the Commission could not properly assess whether potential benefits outweighed the risks, since the level of risk was uncertain, as reflected in the Commission’s decision to impose additional conditions and monitoring arrangements on the company. The Commission counter-argued that uncertainty had not prevented it from establishing that one of the legal conditions for authorisation had been met.

In this case, the Court was not deciding between competing empirical accounts but was called on to ascertain the meaning and conclusions flowing from the scientific opinions. It concluded that RAC had explicitly acknowledged too many shortcomings of the information provided by the company for the Commission to hold that the legal condition for the authorisation had been met.^{Footnote 85} Similarly, as followed from SEAC opinion, the Commission had failed to ascertain that there were no suitable alternatives to the substance.^{Footnote 86} Overall, the Court’s contribution consisted in ensuring that regulatory action at issue was genuinely conditioned and oriented by scientific conclusions. Thus, the Court structured the discretion of risk managers by engaging with the output of risk assessors.

C. Between consistency and reliability

Some cases appear more challenging inasmuch as applicants increasingly contest the substance of scientific opinions, pointing out alleged inconsistencies or underestimated scientific studies that should allegedly change the overall empirical assessment. Often, the applicable law does not determine the required type of evidence, leaving the assessment of its probative value to the decision-makers. In such cases, adjudicators may attempt to apply review techniques based on ubiquitous rather than specialist knowledge, such as calling on the challenged expert administration to explain its assessments intelligibly, consistently and prima facie convincingly to non-specialists. In particular, EU judges scrutinise the contested specialist reasoning in search for ‘comprehensive links’, that is, links that appear intelligible and logical.^{Footnote 87} EU judges may point out inconsistencies and deficiencies in the parties’ submissions^{Footnote 88} and verify compliance with pre-established specialist guidelines and standards.^{Footnote 89} Most importantly, they may require the applicant to comprehensively justify why and precisely how an allegedly missing factor should have changed the overall assessment. Thus, they signal that the burden of persuasion in EU judicial review rests on the applicant’s shoulders.^{Footnote 90} The applicants cannot expect to be successful by simply indicating a ‘weakness’ in the EU administration’s reasoning. They must fully elaborate on this weakness and elucidate the judges as to how it should change the conclusion. In practice, EU judges frequently find the applicants’ arguments to be merely general assertions that do not convince them of manifest errors in scientific reasoning.^{Footnote 91}

Scrutinising the minutiae of logical links in contested scientific reasoning may prove quite potent and, at any rate, perfectly sufficient to solve many cases in which specialist assessments are challenged. This strategy is recommended by Sulyok^{Footnote 92} and arguably conforms with the conception of courts as ‘catalysts’ by Scott and Sturm.^{Footnote 93} But it does not perfectly secure against arbitrariness given the contemporary complexity and uncertainty of empirical issues emerging in EU litigation. It is arguably based more on ubiquitous than specialist knowledge, so it rules out specialist tacit knowledge. In most challenging cases, it may resemble Haack’s analogy of solving an intricate and abstruse crossword puzzle relying on clues and ubiquitous common-sense ways of reasoning only, where the entries are supposed to be given in a foreign language and reflect a system of knowledge utterly alien to the person solving the puzzle. It may also resemble the metaphor of assembling a complex jigsaw puzzle based on the non-unique shapes of the pieces only, not seeing the pictures.

Take a recent case that concerned updating the entry of bisphenol A as a candidate for ‘a substance of very high concern’, the use of which would be subject to prior authorisation under REACH on account of endocrine disrupting properties. The legal condition for identifying candidate substances was that there exists ‘scientific evidence of probable serious effects to … the environment’, which gave rise to ‘an equivalent level of concern’ to the effects of some other substances considered as being of very high concern.^{Footnote 94} The company placing this substance on the market alleged, among other things, that ECHA had wrongly disregarded some reliable studies dispelling the concerns. ECHA applied a ‘weight-of-evidence’ approach, which involved considerable specialist discretion, and which implied that ‘evidence from multiple independent sources of information is considered, while the information from each single source alone is regarded insufficient to support that hypothesis or finding’.^{Footnote 95} The General Court held that it could find a manifest error of assessment ‘only if ECHA completely and wrongly disregarded a reliable study, the inclusion of which would have altered the overall assessment of the evidence so that the final decision would have been implausible’.^{Footnote 96} Then, the General Court meticulously verified the contents of the ECHA decision and its support document to ensure that the reasoning was intelligible, appeared consistent, and offered plausible reasons for certain studies being considered relevant and others irrelevant. It also held that the applicant had not demonstrated how the result of the weight-of-evidence analysis should be altered.^{Footnote 97}

However, a reader of the judgement may be uncertain to what extent the reasons provided by the General Court in this and similar cases imply an independent assessment of the substantive correctness or at least plausibility of the contested specialist reasoning. It is challenging to deduce the level of such an independent assessment from the judicial statement of reasons. Assessing methodological strengths and weaknesses of specific scientific studies might have required considerable specialist knowledge, including tacit knowledge. Even if the General Court was convinced that ECHA’s weight-of-evidence approach appeared plausible, it remains unclear to what extent this judicial assessment was prone to errors. The Court’s reasoning was probably based mainly on ubiquitous reasoning, bereft of tacit knowledge stemming from years of experience in expertly judging the reliability of similar scientific opinions. In particular, the weight-of-evidence exercise, in this case, encompassed multiple studies applying various methods, having different core objectives and different weaknesses, thereby arguably presenting a varying probative value. More precisely, the weight-of-evidence approach is applied when ‘the information from a single piece of evidence alone is not sufficient to fulfil an information requirement’ under REACH. ‘This could be, for example, due to clear deficiencies in one of the existing studies’ or where ‘individual studies provide different or conflicting conclusions’. The weight assigned to the different pieces of evidence ‘depends on factors such as the quality of the data, consistency of results, nature and severity of effects, and relevance of the information’. Crucially, ‘the weight of evidence approach requires use of scientific judgement’,^{Footnote 98} which seems to imply a modicum of subjectivity and, consequently, value judgements as to, for instance, the right balance between the precautionary and evidence-based approaches. Appraising the interrelationship of different pieces of evidence, having a varying probative value, and their overall effect on the conclusion reached by the EU administration seems highly complex. It involves considerable uncertainty and both technical and political discretion.

Interestingly, the applicant argued on appeal that the intensity of judicial review by the General Court had been insufficient and that the Court had imposed on the applicant an ‘unacceptable and unachievable standard of proof’ in demonstrating errors, first, in the assessment of individual studies and, second, in these errors’ impact on the overall weight-of-evidence analysis. In this applicant’s view, the General Court allowed ECHA to make an arbitrary choice of scientific studies. In other words, the appellant seemed to expect the General Court to form an independent view on the correct or at least plausible outcome of the weight-of-evidence exercise. Could the General Court be realistically expected to perform such an intellectual operation? Even if it had appointed expert witnesses, how would it have assessed subsequent allegations against these experts’ opinions? How could such court-appointed experts match the authority of dozens of experts involved in the decision-making of the ECHA and of the Commission? Ultimately, the Court of Justice did not find errors in the General Court’s overall approach or any obvious distortions of evidence.^{Footnote 99}

This is not to say that the General Court’s reasoning in this case was flawed or that the outcome was incorrect. The Court might have been perfectly right. Nor is the point that the Court could have done more. The significance of institutional conditions and ensuing limitations has already been explained. In fact, in this and other similar cases, it is not entirely clear whether the court acts as a ‘super expert’ or only reviews the internal consistency of the contested specialist reasoning. However, the institutional context and some characteristic formulationsFootnote ¹⁰⁰ may suggest that the latter is the case. Generalist adjudication might have reached its innate limits in this regard. Similar judicial strategies may remain the only choice of adjudicators operating in adversarial frameworks when the applicants do not present a lucid, accessible, and compelling account of why and how the contested specialist analysis has been distorted. However, an assessment that seems intelligible, internally consistent, and ultimately plausible to a layperson not sufficiently familiar with limits and criticism of commonly accepted specialist practices, alternative methodologies, and other vital nuances may be assessed differently by a specialist who has acquired large amounts of tacit knowledge and mastered the scientific ‘refinements’ of everyday and common-sense inquiry. Moreover, the said judicial techniques may imply concealed deference to specialist administration, expected to satisfy only the standard of internal consistency rather than substantive accuracy. After all, they may not directly address the crux of the issue, namely the probative value of evidence or the soundness of scientific reasoning. However, they may create an impression of thorough review by generating long paragraphs of judicial text, appearing at least as intricate as the specialist reasoning subject to review.

In another recent case concerning a magnetic resonance imaging contrast agent product, the European Medicines Agency (EMA) scientific committees found that scientific studies had shown that a substance used in this and other contrast agents, gadolinium, accumulates in the human brain. The long-term clinical consequences of such accumulation remained unknown as the long-term safety data was limited. Adverse neurological effects could not have been ruled out at that stage, although no such effects had yet been demonstrated. Despite disagreements within and between committees, it was considered that the risk-benefit balance of the product in question was no longer favourable.^{Footnote 101} The Commission suspended the market authorisation for gadolinium-containing contrast agents, including the product in question. According to the applicable legal framework,^{Footnote 102} the market authorisations of medicinal products could be suspended if, among other things, their risk-benefit balance was no longer favourable. Considering the precautionary principle, the Commission could rely on data not ruling out scientific uncertainty, but its decision should be substantiated by ‘new, objective, scientific or medical data’.^{Footnote 103}

In essence, the General Court had to assess whether the finding that gadolinium accumulates in the brain could plausibly make the risk-benefit balance for the product in question unfavourable despite the remaining uncertainty. The applicant contended, among other things, that the EU administration reversed the burden of proof, requiring the applicant to prove with certainty the absence of adverse neurological effects. Addressing this point, the General Court referred to the reasoning presented by the EMA committee, finding it sufficiently plausible. The Court summarised this reasoning, according to which contrast agents such as the product in question were retained in the brain at a 10-fold higher magnitude than other gadolinium-containing agents and remained there for up to 1 year or more. Although no study showed clinical signs of neurotoxicity, the committee considered that the available data was limited and that such clinical signs may be delayed and subtle. Various unknown factors may obstruct their spontaneous reporting. The Court then referred to the committee’s consideration of different available studies. Although all were characterised by uncertainty, the Court concluded that the committee ‘relied on an assessment of objective scientific or medical data which do not rule out any scientific uncertainty, but which could nevertheless be serious and conclusive evidence’ of the accumulation in the brain and potential toxic effects of the substance in question.^{Footnote 104}

Considering again the general institutional context and, in this case, the General Court’s reliance on the opinions of the EMA committees, a reader of this judgement might wonder whether the court confirmed the cogency or at least the internal consistency of the committees’ reasoning or, in fact, rather deferred to it in a concealed way. Crucially, the General Court relied heavily on the precautionary principle, which did not require ‘solid and persuasive evidence’ but only ‘serious and conclusive evidence’, arguably implying deference to the administration.^{Footnote 105}

The judicial review of the internal consistency of scientific opinions leads to distinct challenges in cases where the applicants contest conclusions drawn from the evidence gathered by the EU administration. Ideally, verifying whether such conclusions are substantiated requires in-depth specialist knowledge of the relevant field from the reviewer. A sufficiently specialised reviewer could conceive of alternative interpretations of evidence and assess whether the chosen interpretation is the most plausible compared to other possibilities. Generalists have difficulty doing that.

This challenge may be illustrated by a recent case brought to the EU Courts by three environmental organisations.^{Footnote 106} These organisations challenged the Commission’s refusal to review its authorisation of genetically modified soybeans. The crux of the dispute lay in whether the Commission committed a manifest error of assessment in drawing conclusions from the available scientific data. The applicants claimed to have shown ‘legitimate and substantive doubts’ about the modified soybean’s safety, while the legal conditions for the authorisation were that, in particular, the genetically modified food or feed must not have adverse effects on human health, animal health or the environment.^{Footnote 107} However, the EU Courts held that the applicants must rather show ‘serious doubts as to the lawfulness of the authorisation decision’, thereby imposing a higher standard of proof on the applicants.^{Footnote 108}

Nonetheless, in the applicants’ view, the Commission and the European Food Safety Authority (EFSA) should have further investigated the concerns or found that the modified soybean was not safe.^{Footnote 109} The applicants argued, among other things, that EFSA failed to require the producer to properly investigate the potential effect of specific biotic (e.g. viruses or insects) and abiotic (e.g. temperature) stressors on the modified soybean when sprayed with glyphosate or other maintenance pesticides. Evidence suggested some consequences on food safety based on studies on other cultivations. Moreover, the applicants claimed that EFSA had not required a sufficient toxicity assessment, given concerns from the available literature.^{Footnote 110} EFSA counter-argued that these issues were irrelevant because of the soybean’s intended uses. Also, it found statistically significant differences in only 9 out of 334 comparisons between the modified soybean and its natural comparator after applying biotic stressors and no differences when applying abiotic stressors.^{Footnote 111}

The General Court admitted that some of the Commission’s reasons were ‘very succinct and … limited to the finding that the scientific publications in question were taken out of context and provided no new information that might change the conclusions on the toxicity assessment of the modified soybean’.^{Footnote 112} Nonetheless, having referred to the Commission’s explanations, which seemed sufficiently plausible,^{Footnote 113} the General Court found no manifest error of assessment. On appeal, AG Szpunar confirmed a ‘strong presumption of correctness’ of the EU administration’s scientific appraisals, which was for the applicant for judicial review to rebut.^{Footnote 114} The Court of Justice concurred.^{Footnote 115}

Notably, in this case, the applicants might have effectively expected the EU Courts, again, to express an independent opinion of the soundness of the Commission and EFSA’s conclusions drawn from the available data. In the applicants’ view, the General Court instead imposed on them an impossible standard of proof,^{Footnote 116} requiring them to show manifest errors in the contested assessments based on new evidence.^{Footnote 117} As noted by Leonelli, this legal controversy boiled down to a divergent evaluation and interpretation of available scientific evidence and the difference of view regarding the appropriate EU level of precaution about genetically modified organisms.^{Footnote 118} The applicants adduced no ‘new’ scientific evidence but, instead, aimed at indicating the weak points of the Commission’s assessment, which might, in their view, make the entire assessment too uncertain to justify the authorisation. However, where many abstruse and intricate issues regarding detailed stages of a complex assessment are raised, a satisfactory review of its plausibility may require specialist knowledge, including tacit knowledge. Hence, the General Court expected the applicants to discharge the burden of proof.

It should be added that, in general, civil society expresses concerns about the EU administration’s specialist assessments, considering that they are often based on the review of internal consistency of studies produced by the interested industry.^{Footnote 119} There are also concerns about the neutrality of the industry’s experts.^{Footnote 120} This institutional context partly explains why the pressure on the judicial epistemic capacity to engage with specialist appraisals has been mounting. Moreover, similar concerns have been expressed about structural arrangements at the EU Courts. In brief, due to the restrictive standing criteria, the EU Courts are usually confronted with the evidence produced by the affected industries.Footnote ¹²¹

D. Super-experts

Over time, courts facing repeated legal challenges in areas requiring specialist knowledge may feel sufficiently confident to form independent assessments of the probative value of scientific evidence and the soundness of specialist reasoning.^{Footnote 122} This does not necessarily mean that such judicial review ensures a better protection from arbitrariness. Quite the opposite, it led Vos to express concerns about whether generalist judges should assume the role of ‘super experts’.^{Footnote 123} In some cases, the General Court seems confident enough to provide its independent assessment of scientific evidence and reasoning,^{Footnote 124} occasionally finding even ‘manifest errors of assessment’. Although it is difficult to indicate clear criteria for such ‘manifest’ errors, these errors may be linked to insufficient justifications of uncertain, potentially controversial, and usually precautionary assumptions.^{Footnote 125} As mentioned, some of such implicit assumptions may seem evident and plausible to experts based on their commonly shared tacit knowledge. Nonetheless, in view of the duty of care, such assumptions may need to be made explicit. Thus, the dividing line between the duty to state reasons and the duty of care becomes blurred, just like the dividing line between the review of manifest errors and the substitution of specialist appraisals becomes blurred, at least to some litigants^{Footnote 126} and commentators.^{Footnote 127}

For instance, a recent case concerned the classification of titanium dioxide as carcinogenic, resulting in legal requirements being imposed on its marketers.^{Footnote 128} Titanium dioxide is an industrial substance used in white pigments and foodstuffs. Manufacturers, importers, downstream users, and suppliers of titanium dioxide challenged a scientific study that formed the basis of ECHA’s assessment, alleging a manifest error of assessment. In essence, they put in question the methodology of that study, conducted on rats, arguing that the lungs of the animals had been excessively overloaded with the substance, yielding incorrect results. The applicants contended that the relevant particles agglomerate, resulting in lower density, and that if the ECHA had drawn correct conclusions from previous studies, it would have concluded that the main study was methodologically unreliable.^{Footnote 129} The Commission counter-argued that the applicants expect the court to substitute its own opinion on the correct scientific conclusions to be drawn from this and other studies for that of the ECHA, which would go beyond the confines of judicial review.^{Footnote 130} Moreover, the Commission argued that, faced with incomplete data, ECHA seems to have made some precautionary assumptions about the standard density of the substance and explained in detail additional factors that it considered.^{Footnote 131}

The General Court assessed the probative value of the study by referring to reservations of the French competent authority. It found that the agglomeration of particles resulting in lower density – a phenomenon the parties did not contest – was a relevant factor that the ECHA and the Commission had not sufficiently considered, thereby committing a manifest error of assessment.^{Footnote 132} Crucially, the General Court insisted that its standard of review was not triggered by a substantive disagreement with the scientific conclusions but rather consisted in a procedural check of ‘all relevant factors’.^{Footnote 133} However, France appealed this judgement, arguing that the General Court distorted the study in question and substituted its own assessment for that of the competent administration, thereby exceeding the limits of judicial review. The appeal is currently pending.Footnote ¹³⁴

How to understand the boundary between considering ‘all relevant factors’ and making or changing the substantive assessment? That a factor is ‘relevant’ to a conclusion means that it affects the degree in which this conclusion is supported by all the factors (evidence) overall.Footnote ¹³⁵ Therefore, assessing relevance is not purely ‘procedural’ as it cannot be dissociated from assessing the ‘substantive’ value of a factor or a piece of evidence in the overall specialist assessment. Performing the test of ‘all relevant factors’ may require specialist knowledge. Hence, without making any assumptions as to where the truth lay in the case of titanium dioxide, one should be in any case aware that skilled litigators could possibly succeed in convincing generalist judges that the administration has committed a scientific error, overlooking a relevant factor, where grounds for finding such an error could appear contestable to experts possessing specialist tacit knowledge.

Recently, another case presented a disagreement over a choice between two methodological frameworks for assessing the aquatoxicity of a particular composite type of tar.^{Footnote 136} The method chosen by the EU administration, the ‘summation method’, disregarded a specific factor, namely, the low solubility of the substance as a whole. Instead, this method consisted of assessing the substance’s components, resulting in the overestimation of risk to the natural environment. The alternative method advanced by the applicants, the ‘water accommodated fraction approach’ would consider the low solubility of the substance as a whole, but it would lead to the underestimation of risk.Footnote ¹³⁷

In its relatively brief analysis, the General Court noted that the EU administration did not provide any reasoning demonstrating that it had taken the low solubility into account. The EU administration’s defence strategy relied on arguing that the applicable EU legislation did not allow this factor to be considered. The General Court swiftly dismissed this argument, holding that the administration must consider all relevant factors, an approach endorsed by the Court of Justice. Leonelli questioned whether the ‘missing’ factor could have been really considered, from the scientific point of view, without determining how exactly the risk would be assessed.^{Footnote 138} In other words, the common-sense logic of requiring the administration to consider ‘all relevant factors’ might have been unreliable. A decision to include or disregard a specific factor in the analysis could be underpinned by an implicit specialist assessment considering limitations of available methodological approaches. Therefore, for Leonelli, this case exemplified ‘quasi-substantive review’. In fact, she suggested that the EU administration’s defence strategy might have misled the EU Courts. Hence, she argued that the administration should have rather openly acknowledged and defended its political and technical discretion to choose the more precautionary approach, and consequently choose a specific methodological framework disregarding certain factors, in line with the precautionary principle.^{Footnote 139}

If this criticism concerning the inexistence of a middle ground between the two methodological approaches was valid, something which cannot be decided here (as doing so would require specialist knowledge), one could take this case as a potential example of the epistemic limits of generalist judges in handling complex and uncertain appraisals, even following the logic of the process-oriented review of ‘all relevant factors’ and the like. One could also wonder to what extent a flawed defence strategy presented in an essentially adversarial procedural setting before generalist judges may obfuscate the nature of scientific choices and their nuanced connection to value judgements, with unexpected consequences for the final ruling. The absence of specialist tacit knowledge may lead to either overly deferential or inadvertently intense scrutiny. Hence, specialist knowledge may also be necessary for adjudicators to recognise where (informed) deference should be applied to avoid further risks of epistemic trespassing and, consequently, (judicial) arbitrariness.

A. Institutional and legal contexts

By incorporating a degree of specialist knowledge, administrative review by the boards of appeals was supposed to provide more thorough scrutiny of complex agency decisions while keeping the bulk of complex cases out of the EU Courts’ docket.^{Footnote 140} This is why appeals to the BoAs are mandatory before lodging an action to the EU Courts. In case of a subsequent court action, the General Court examines the BoA decision as formally setting out the agency’s final position.Footnote ¹⁴¹ Appeals can be lodged against the agency’s decisions listed in the founding regulations.Footnote ¹⁴² The founding regulations also decide whether the BoA can only annul (like the EU Courts) or also modify the contested decision. Most BoAs act on an ad hoc basis as the relatively low number of appeals does not warrant a permanent structure. The ad hoc character may constitute an obstacle to accumulating specialist knowledge and hammering out a thorough standard of administrative review.Footnote ¹⁴³

Among the BoAs, ECHA BoA faces the most cutting-edge scientific appraisals. Formally, it can modify the contested decisions,Footnote ¹⁴⁴ but it does not do so, in principle. Additional investigations from the ECHA are usually required following the annulment of contested decisions. The ECHA BOA’s output is significant (dozens of final decisions regarding the merits of appeals in 2006–2022). It also functions as a permanent body, although it relies on the assistance of alternate ad hoc members. Its adjudicatory panel comprises three members only, including one technically qualified member.Footnote ¹⁴⁵

Three elements of the institutional structure of the BoAs, and in particular the ECHA BoA, are relevant. First, thanks to its mixed composition, proximity of the agency, expert resources, and specialisation in a single policy area, the BoAs may be expected to possess a certain degree of interactional specialist knowledge or develop scientific connoisseurship. Therefore, its own empirical appraisals may be informed by specialist tacit knowledge.

Second, just like in the case of the EU Courts, the reasoning of the BoAs and the intensity of administrative review are conditioned mainly by the arguments and evidence (and their elucidation), as provided by the parties.^{Footnote 146} However, the procedural practice of the BoAs may be less formalistic. During oral hearings, the ECHA BoA allows for more direct interactions with and between the parties, represented by lawyers and scientific experts alike.^{Footnote 147} In such a procedural context, one can expect a more intense transfer and absorption of specialist knowledge by the adjudicators.

Third, the ECHA BoA does not, however, engage in independent fact-finding (such as commissioning expert opinions) so as not to replicate the agency’s decision-making process and not to prolong the proceedings. Nonetheless, the institutional setting makes it somewhat more likely for this BoA to autonomously assess the probative value of scientific evidence and the soundness of specialist reasoning presented by ECHA. And yet, this setting does not warrant that the ECHA BoA will always be able to make a ‘better’ scientific assessment than dozens of specialists participating in the ECHA decision-making.

The legal framework that the ECHA BoA is confronted with, particularly REACH, is replete with under-determined concepts requiring reaching out to specialist knowledge such as ‘risks to human health and the environment’ or an ‘adequate control’ of the risk. This legal under-determinacy and the limited steering capacity of law constituted a challenge for a partly specialised body, such as the ECHA BoA, just like for the generalist EU Courts. In practice, the ECHA BoA acts as the guardian of the non-arbitrariness of the precautionary principle, which also plays an essential role in its reasoning.^{Footnote 148} Responding to appeals brought by the chemical industry, the BoA verifies whether the ECHA had sufficient grounds to identify an issue of concern to public health or the environment and adopt administrative measures.

B. Judging the quality of science

Like in the case of the EU Courts, the intensity of review in specific cases before the ECHA BoA depends on the pleas in law raised, arguments advanced, and the evidence adduced by the appellants. To solve certain disputes, the ECHA BoA can avail itself of standard adjudicatory techniques. It may ascertain the parts of empirical assertions that the appellants have not contested and verify the conclusions drawn from these assertions.^{Footnote 149} It may simply clarify the meaning of the contested decision to the appellants.^{Footnote 150} In some cases, the appellants seem unable to elucidate and substantiate sufficiently their arguments against the ECHA’s position. In such cases, the ECHA BoA recalls that the burden of proof and persuasion rests on the shoulders of appellants.^{Footnote 151}

The ECHA BoA has transplanted the case law regarding process-oriented review. Consequently, it verifies the accuracy, reliability, consistency, and comprehensiveness of relevant evidence, which should be capable of substantiating the conclusions drawn from it.^{Footnote 152} The General Court recently clarified that the ECHA BoA should be able to identify ‘errors’ in the ECHA’s appraisals, but it should not be expected to conduct de novo review.^{Footnote 153} Notably, the General Court distinguished ‘manifest errors of assessment’ from ordinary ‘errors’. The Court can annul EU legal acts based on the former, whereas the ECHA BoA can also annul or modify the ECHA decisions based on the latter. This distinction implies a more intense standard of administrative review than judicial review. However, which errors are ‘manifest’ to adjudicators mainly depends on the lucidity and strength of argumentation presented by the litigants. Therefore, indicating criteria to differentiate manifest from ordinary errors seems challenging.

Notably, the ECHA BoA’s reasoning suggests that it does not shy away from expressing its own view on the probative value of scientific evidence (usually, scientific articles reporting on chemical studies),^{Footnote 154} the reliability of specific studies or tools and conclusions drawn from the available data^{Footnote 155} while considering technical limitations of particular methodologies.^{Footnote 156} As the ECHA BoA put it, ‘in conducting its administrative review of Agency decisions, the Board of Appeal possesses certain technical and scientific expertise which allows it to enter further into the technical assessment made by the Agency than would be possible by the European Union Courts.’^{Footnote 157} In other words, considering its institutional setting, the ECHA BoA may benefit from its independent specialist tacit knowledge rather than only explicit knowledge provided mainly in a written form by the parties.

A review of recent decisions suggests that the ECHA BoA indeed evaluates independently the probative value of scientific evidence and the soundness of specialist reasoning underpinning the ECHA’s decisions to request further information from the registrants on substances raising concerns.^{Footnote 158} For instance, in a recent case, the BoA assessed the value of a predictive model concerning the persistence of metabolites of an antioxidant in rubber mixtures used to produce tyres. The appellants argued that ECHA had been wrong to require further tests, having considered that the substance posed an environmental hazard. The model used by the appellant, although confirming that the substance itself was persistent, predicted that its metabolites were less so. The BoA found the model to constitute ‘a deductive chain’ in which ‘the identity of the metabolites can be predicted, their polarity deduced from their identity, and their persistence from their polarity.’ The BoA considered the conclusions drawn from this model as too uncertain unless corroborated with further data.^{Footnote 159}

However, the BoA was at the same time of the view that the specific study requested by the ECHA concerning the metabolites would be hindered by the substance’s low solubility. It relied on OECD guidelines and a scientific report criticising that study. It concluded that the ECHA could not oblige the appellants to achieve specific results but only to make reasonable efforts to identify the metabolites.^{Footnote 160} Interestingly, Germany challenged the latter BoA decision before the General Court, seeing this instance of administrative review as too intense. It argued that the test chosen by the ECHA was state-of-art at that time. However, the General Court did not find an error in the applied standard of review and the BoA’s assessment.^{Footnote 161}

The BoA may also scrutinise the probative value of competing scientific evidence. In a case concerning the evaluation of certain aluminium salts, the appellants questioned the ECHA’s assessment that there was a genotoxicity concern to be clarified. The appellants alleged, among other things, that the ECHA requested further information on genotoxicity based on unreliable in vivo and in vitro studies. In contrast, it disregarded the appellants’ high-quality in vitro studies showing no genotoxicity. The BoA assessed the appellants’ studies as more reliable, noting that studies relied on by the ECHA had deficiencies in reporting and deviations from the OECD guidelines. The ECHA had acknowledged these deficiencies but had not drawn appropriate conclusions.^{Footnote 162}

C. Informed and overt deference

Specialist knowledge may help adjudicators to decide when and how to apply deference that is likely to be ‘informed’. As mentioned, deference should also be ‘overt’ to allow the audience to understand the degree and reasons for it. For instance, in one of the cases before the ECHA BoA, the parties used different calculation methods and categories to assess a change in maternal body weight after exposure to the investigated substance and, thus, the severity of this substance’s maternal toxicity. In the absence of legislative guidance, the BoA considered as sufficiently authoritative a categorisation assumed in a study relied on by the appellants themselves, and it upheld the ECHA decision. However, it noted that even the relevant annex to the CLP Regulation^{Footnote 163} acknowledged that this was ‘a complex issue because of uncertainties surrounding the relationship between maternal and developmental toxicity’.^{Footnote 164} Although the ECHA BoA noted that ECHA did not fully explained how it arrived at its conclusions, it did not find these conclusions unreasonable. Openly acknowledging and justifying the deference arguably helps maintain public trust in the ability of adjudication to remain vigilant and rule out the risk of arbitrariness.

Crucially, the ECHA BoA sometimes invokes the concept of a ‘scientific disagreement’ or a ‘difference of scientific opinion’ between the parties. Such scientific disagreements are insufficient to find that the ECHA has committed an error of assessment.^{Footnote 165} The purpose of this concept is not entirely clear, but it seems to emphasise the relatively high threshold of proof and persuasion imposed on the appellants. It also seems to justify a degree of the BoA’s deference to the ECHA in cases where scientific assessments remain uncertain. The adjective ‘scientific’ is often but incorrectly used as a synonym of ‘reliable’.^{Footnote 166} Therefore, it may be interpreted as marking cases in which the BoA chooses to defer to the ECHA without denying the uncertainty of the ECHA assessment and, at the same time, the reasonability of appellant’s scientific counter-arguments. The BoA explained in this regard that ‘the data available for substance evaluations is in some cases inconsistent or indeed contradictory and in other leave questions open. It is therefore not surprising that there is often a difference of opinion between experts when assessing the available data’.^{Footnote 167} As a ‘scientific disagreement’ or ‘difference of scientific opinion’ implies that the arguments of both parties are reasonable, from the scientific point of view, the BoA seems to implicitly confirm that the ECHA’s assessment, although uncertain, is not arbitrary. This kind of ‘informed’ deference arguably implies a substantive check on the exercise of discretion by the administration. In this sense, informed deference is compatible with the conception of the rule of law as the pursuit of non-arbitrariness. It does not risk leaving the duty of care unenforced.^{Footnote 168}

For instance, the BoA dealt with a case concerning whether tumours caused by a substance, observed in rodents, were due to a receptor specific to these animals and, consequently, whether there was a concern about human health. The BoA began by noting a strong presumption that tumours induced by the substance are relevant to humans, based on the wording of an annex to the CLP Regulation.^{Footnote 169} Substances inducing tumours in well-performed experimental studies on animals are considered human carcinogens unless there is ‘strong evidence’ that the tumour formation mechanism is irrelevant for humans.^{Footnote 170} Subsequently, the BoA reflected upon the conclusions that could be drawn from the available scientific studies.^{Footnote 171} It also checked these conclusions with other available studies.^{Footnote 172} It noted that the existing evidence did not amount to final proof of whether the receptor at issue, which the humans do not have, was decisive in the formation of tumours by the substance under examination or whether there were also other modes of action. The BoA found here a ‘scientific disagreement’ and ‘diverging scientific opinion’ between the parties, not sufficient to demonstrate an error by the ECHA.^{Footnote 173} Ultimately, it relied on the precautionary principle^{Footnote 174} and upheld the ECHA’s concern.

Interestingly, the General Court dealt with a similar issue in another case, styling its reasoning in a somewhat different way that suggested the review of ‘consistency’ of the ECHA opinion. The Court stressed the prima facie plausibility of ECHA opinion and the fact that the scientific uncertainty at issue was acknowledged and considered therein. The Court highlighted the applicant’s responsibility to adduce evidence making the opinion implausible, but it provided no hints as to whether the applicant’s reservations were reasonable or not. Therefore, it was unclear how ‘informed’ the judicial review in this case was. In fact, the Court might have concealed deference by focusing on the internal consistency of the assessment.^{Footnote 175}

Another somewhat similar case concerned the evaluation of triclosan, a broad-spectrum antibacterial commonly used in hygiene products. The appellant contested ECHA request for further studies because, in its view, the requested enhanced developmental neurotoxicity study would not produce useful information, among other things.^{Footnote 176} The appellant contended that the existing data in rats, in combination with human clinical data, did not warrant further animal testing for neurotoxicity or reproductive toxicity due to considerable evidence that the rat and human thyroid systems differ. The BoA identified here again a difference of scientific opinion.^{Footnote 177} It was satisfied that the ECHA admitted uncertainty, while explaining why the requested state-of-art studies might still produce useful information.^{Footnote 178} The appellant challenged this decision before the General Court alleging an insufficient standard of administrative review. However, the Court found the BoA standard sufficient, even if involving a degree of deference.^{Footnote 179} In brief, the Court seemed satisfied with administrative review implying ‘informed’ and ‘overt’ deference.