## Facts

- During World War II, Regulation 18B of the Defence (General) Regulations 1939 authorized the Home Secretary to detain a person if the Home Secretary had reasonable cause to believe the person was, among other things, of “hostile associations,” and that detention was necessary.
- On May 22, 1940, Home Secretary Sir John Anderson made a detention order against Ben Greene stating that Anderson had reasonable cause to believe Greene was a “person of hostile associations” and should be detained under Regulation 18B.
- Greene was arrested and held in Brixton Prison beginning May 24, 1940.
- After Anderson left office, the new Home Secretary, Herbert Morrison, continued Greene’s detention under the existing order.
- In March 1941, Greene applied ex parte to the King’s Bench Divisional Court for a writ of habeas corpus, challenging the legality of his detention.
- Anderson filed an affidavit stating that, when he made the order, he relied on reports from persons in responsible positions who had experience in investigations; he did not identify the sources or set out the detailed facts said to support detention.
- Morrison filed a similar affidavit asserting that Greene was a person of hostile associations, again without giving specific supporting facts.
- Greene filed an affidavit alleging that his detention was politically motivated and amounted to political persecution rather than a genuine security measure.
- The Divisional Court refused the writ. Greene appealed to the Court of Appeal.

## Issues

1. Whether, on habeas corpus, a court may examine the sufficiency of the information said to justify a Regulation 18B detention where the detention order is valid on its face.
2. Whether the phrase “reasonable cause to believe” in Regulation 18B requires an objective showing of reasonable grounds to the court, or instead turns primarily on the Home Secretary’s honest satisfaction formed within the regulation.

## Decision

- The Court of Appeal dismissed Greene’s appeal and affirmed the Divisional Court’s refusal of habeas corpus.
- The court held that the detention order, which recited the Regulation 18B condition (“reasonable cause to believe” hostile associations), was valid on its face and supported continued detention.
- The court declined to require the Home Secretary to disclose the particular facts, sources, or intelligence said to justify the belief stated in the order and affidavits.
- The court treated the formation of the relevant belief under Regulation 18B as a matter for the Home Secretary, subject to limited judicial control.
- The court found no adequate basis on the evidence before it to conclude that the Home Secretary acted in bad faith or outside the scope of Regulation 18B.

## Legal Principles

- On an application for habeas corpus challenging detention under Regulation 18B, when the Crown produces a detention order that is valid on its face, the court will not ordinarily inquire into the sufficiency or weight of the grounds on which the Home Secretary acted.
- “Reasonable cause to believe” in Regulation 18B is construed in a manner that gives primary responsibility to the Home Secretary’s honest assessment; it does not generally invite the court to decide whether the available material would objectively satisfy a judicial standard of reasonableness.
- Non-disclosure of confidential sources and detailed security information does not, by itself, make a Regulation 18B detention unlawful.
- Judicial intervention remains possible where the detention is outside the regulation (jurisdictional error), where the order is defective on its face, where the wrong person is detained, or where bad faith (mala fides) is shown.

## Conclusion

Rex v. Secretary of State for Home Affairs (Court of Appeal 1941) upheld Ben Greene’s wartime detention under Regulation 18B, holding that once a facially valid detention order is produced, habeas corpus review is generally limited to legality on its face and proof of bad faith or action outside the regulation, rather than an assessment of the underlying evidence or its adequacy.


Rex v. Secretary of State for Home Affairs, Court of Appeal 1941