U3 v Secretary of State for the Home Department

The Supreme Court considered the role of the Special Immigration Appeals Commission (SIAC) in appeals concerning national security assessments made by the Secretary of State in relation to deprivation of British citizenship under section 40 of the British Nationality Act 1981 and refusal of entry clearance. The court held that where the question is whether a decision is justified on grounds of national security, SIAC’s task is not to re‑decide every disputed fact on the balance of probabilities but to determine whether the evidence as a whole provides a rational basis for the Secretary of State’s evaluative judgment. SIAC may admit and consider evidence that was not before the original decision‑maker and may make findings of fact on the balance of probabilities where the legal issue requires such findings (for example, statelessness or factual matters relevant to article 8), but when assessing national security risk it must apply public law review principles and give very considerable weight to the Secretary of State’s assessment, taking account of the institutional and constitutional allocation of responsibility.

The appellant (designated U3) appealed the Secretary of State’s decisions to deprive her of British citizenship under section 40(2) of the British Nationality Act 1981 and to refuse her entry clearance; both decisions were certified on national security grounds and the appeals lay to SIAC under sections 2 and 2B of the Special Immigration Appeals Commission Act 1997. The appellant had travelled to ISIL‑controlled territory with her then husband and challenged the Secretary of State’s assessment that she was aligned with ISIL and posed a national security risk. The appeals were heard by SIAC (which dismissed them), the Court of Appeal (which dismissed the further appeal) and then by the Supreme Court.

The issues for the court included:

• the proper effect of this court’s decision in R (Begum) v SIAC and the earlier decision in Rehman on SIAC’s functions;
• whether SIAC should make its own findings of central facts relevant to national security (on the balance of probabilities) and, if so, remit the matter to the Secretary of State where the Secretary of State’s factual basis was shown to be materially incorrect; and
• whether the procedure met Convention standards, particularly where article 8 rights of the appellant’s children were engaged.

The court explained the statutory and procedural context: appeals under sections 2 and 2B are appellate in form and may involve fact-finding, evidence not before the original decision‑maker and updated assessments by the Secretary of State during the appeal; however, the assessment whether a person presents an unacceptable risk to national security is an evaluative judgment involving precautionary or predictive reasoning which differs from ordinary civil fact‑finding on a balance of probabilities. The proper task for SIAC when considering national security risk is to review, applying public law principles, whether the Secretary of State’s evaluative judgment had a proper factual basis and was one which could reasonably be held; SIAC should give very considerable weight to the Secretary of State’s assessment because of institutional expertise and constitutional allocation of responsibility.

The court applied these principles to the facts: SIAC had carefully scrutinised the evidence (including closed material) and concluded that a rational basis existed for the Secretary of State’s assessment that the appellant was ideologically aligned with ISIL and posed a national security risk; SIAC also carried out an independent article 8 assessment of the children’s best interests and concluded that, on balance, national security concerns outweighed the interference with the children’s family life. The Supreme Court found SIAC’s approach correct (save for a non‑material misunderstanding about the temporal scope of evidence), upheld the Court of Appeal, and dismissed the further appeal.

The appeal was dismissed. The court held that SIAC’s role in reviewing national security assessments is not to re‑decide every disputed factual matter on the balance of probabilities but to assess, applying public law principles, whether the evidence as a whole provides a rational basis for the Secretary of State’s evaluative judgment about national security risk. SIAC may make fact findings where the legal issue requires them, may consider evidence not before the original decision‑maker, and must give very considerable weight to the Secretary of State’s assessment; applying those principles, SIAC’s dismissal of both appeals was lawful.

SIAC dismissed both appeals (deprivation of citizenship and refusal of entry clearance). The Court of Appeal dismissed the appellant’s appeal from SIAC: [2023] EWCA Civ 811; [2024] KB 433. The present appeal to the Supreme Court was dismissed: [2025] UKSC 19.