The Judgment of Fordham J in R (EXR) v SSHD (2026) EWHC 1568 (Admin) contains a passage as follows:-
“The rubric of judicial review
- Decisions of public authorities must be lawful, in a public law sense. That means – in broad terms – that they must be legal, reasonable and fair. To decide whether they are, the judicial review Court applies objective legal standards. Legality is really concerned with two things: whether the public authority has performed its substantive legal duties; and whether it has made correct conclusions on questions of Fairness is concerned with the legal legitimacy of the public authority’s decision-making process. Reasonableness asks whether an outcome of a decision was beyond the range of responses open to the public authority; and whether the reasoning process involved any recognisable public law error of approach. Sometimes there are nuances and overlaps. There is a species of public law error which involves a material error of an established fact, but nobody says that is relevant to the present case. There is a species of public law error which involves a decision as to a factual question whose lawfulness depends on its correctness, which is highly relevant to the present case.
Reasonableness standard of review
- Deeply embedded in the philosophy of judicial review, where the Court is concerned with evaluative questions entrusted to the primary judgment of the public authority, is the reasonableness standard of review. The public authority’s decisions and conclusions depend, for their lawfulness, on whether they are The standard of review is not substitutionary. There is a margin for error. The reasonableness standard of review also conventionally carries with it a restrained approach to evidence, judging reasonableness by reference to the evidence available to the public authority at the time of the impugned decision. …”
“Correctness standard of review
- In some situations, a public authority’s decisions and conclusions depend, for their lawfulness, on whether they are correct. That includes decisions and conclusions on questions of law. But it can include decisions and conclusions on questions of fact. …”
“The distinction between interpretation and application
- Whenever public authorities and the Courts are considering an instrument having a legal effect – whether it is primary legislation or a set of rules or policy guidance – there is always an important basic distinction between interpretation and application. The interpretation of the instrument is a question of law, attracting the correctness standard of review. The application of the instrument is an evaluative question for the public authority as primary decision-maker, attracting the reasonableness standard of As Lady Hale explained in R (A) v Croydon LBC [2009] UKSC 8 [2009] 1 WLR 2557 (at §§21, 23), “[t]he court decides what the words mean”; but “the authority decides whether the facts fit those words”, “subject to the scrutiny of the courts on the ordinary principles of judicial review”. The same distinction applies to policy guidance. As Lord Reed explained in Begum at §124: public authority decisions can be “successfully challenged on the ground that the relevant authority … misdirected itself as to the meaning of its policy”; whereas “the question how the policy applies to the facts of a particular case is generally treated as a matter for the authority, subject to the … requirement of reasonableness”.
- Importantly, this distinction between interpretation (correctness standard) and application (reasonableness standard) has been recognised in cases which are about Home Office policy in which there are protections for a “child” …”
“Knock-on effect unlawfulness
- The unlawfulness of public authority action can depend on the unlawfulness of previous public authority action. If a decision to deport or remove a person is unlawful, the exercise of the power to detain them for deportation or removal is in consequence unlawful. The detention is “for the express purpose of facilitating deportation”. It is “artificial and unwarranted” to “divorce the detention from the deportation”. The deportation decision is “a prerequisite to” the detention and “the edifice on which the detention is founded”. The lawfulness of the detention is “referable back to the legality of the decision to deport”. It “depends for its legality on the lawfulness of the deportation”. … Another example is where a local authority’s decision that accommodation is suitable is unlawful because it is based on an unlawful prior assessment: see R (Norton) v Haringey LBC [2025] EWCA Civ 746 [2026] PTSR 49 at §§29-31.”
Fordham J went on to consider the application of these principles in various contexts, especially whether a person is a “child” and age assessment and issues, including (paragraphs 13-55) the UK-France Treaty on readmissions (and its exclusion of unaccompanied children), the Home Office Inadmissibility Guidance, the Home Office Assessing Age Guidance, and other p