The landmark House of Lords ruling in Home Secretary v AF (No. 3) [2009] UKHL 28 imposed a ‘core irreducible minimum’ of disclosure (the AF (No. 3) duty) to suspects challenging a control order in judicial review proceedings which necessitated a closed material procedure (CMP) for national security reasons. This chapter outlines the application and impact of that decision in respect of the many other types of proceedings which require a CMP in national security and related contexts. It argues that the judicial treatment of the duty has been inconsistent, meaning that the enhanced procedural protection offered by the AF (No. 3) duty is often not present when the circumstances faced by the litigant are the most serious.
