Double-Lock

Under s.19 of the Investigatory Powers Act 2016, the Secretary of State may issue a targeted interception or targeted examination warrant only where satisfied as to necessity, proportionality and safeguards, and, 'except where the Secretary of State considers that there is an urgent need to issue the warrant, the decision to issue the warrant has been approved by a Judicial Commissioner.' Section 23 governs how that second stage of authorisation works: 'In deciding whether to approve a person's decision to issue a warrant under this Chapter, a Judicial Commissioner must review the person's conclusions' as to necessity and proportionality, and in doing so must 'apply the same principles as would be applied by a court on an application for judicial review'. If the Commissioner refuses approval, the Commissioner 'must give the person written reasons for the refusal', and the person may ask the Investigatory Powers Commissioner to review a refusal by any other Judicial Commissioner.

This dual sign-off — ministerial decision plus independent judicial approval — is the 'double-lock' and extends beyond interception to other Part 5-type intrusive powers such as equipment interference warrants, which likewise cannot generally be issued without Judicial Commissioner approval; the Act's urgency provisions (for example s.109 for equipment interference) confirm this default by carving out a narrow exception where a warrant is issued urgently without prior approval, subject to retrospective review by a Judicial Commissioner within three working days. The double-lock, introduced as a headline reform of the 2016 Act, was intended to add independent judicial oversight to intrusive surveillance decisions that had previously rested with ministers alone.