This Article sheds new light on the long-running debate in EU legal studies about how intense the EU judicial review of complex and uncertain assessments requiring specialist knowledge could and should be. It argues that it is necessary to move beyond formulas and concepts hammered out in the judicial statements of reasons and consider how the institutional context affects legal epistemology. How likely is it that the judges form an independent opinion about the probative value of the presented evidence and the soundness of the administration’s specialist reasoning? How likely is it that their opinion is reliable? Answering these questions helps appraise the boundaries in which judicial review or proliferating administrative review by partly specialised boards of appeal foster the rule of law understood as the pursuit of non-arbitrariness. The Article examines recent case law of the EU Courts and the Board of Appeal of the European Chemical Agency concerning public health and environmental issues, in which complex and uncertain specialist assessments were prevalent. It contends that, due to institutional limitations of EU adjudicatory bodies, a further expansion of the rule of law in EU decision-making requiring specialist knowledge should be pursued through extra-judicial means fostering transparency, inclusiveness, and accountability.