Why proportionality is not a general ground of judicial review

Proportionality is a relation between two things held, metaphorically, in either side of a balance. Proportionality is a ground of judicial review of executive decisions when and only when the law requires judges to hold the scales, and to weigh one set of interests against another. That can be a just and convenient way for the law to give special protection for interests that call for that protection (as the law of the European Convention on Human Rights and European Union law do, and the common law does in some circumstances). Proportionality should not be a ground of judicial review (1) if a claimant can assert no interest that ought to be protected by proportionality reasoning, or (2) if the weighing ought not to be done by a court. As a result, proportionality can never be a general ground of judicial review of administrative action. The grounds of judicial review are various and depend on the nature of an administrative decision. In fact, there is no general common law ground of judicial review of the substance of administrative decisions. Not even Wednesbury unreasonableness. I will explain this view by pointing out the good sense in the famous, albeit flawed, 1948 decision of the Court of Appeal in Associated Provincial Picture Houses Ltd v Wednesbury Corporation