After the Snowden revelations, Britain’s Investigatory Powers Tribunal (IPT), an administrative panel dealing with illegal interception of communication, heard a series of complaints from NGOs. The Tribunal sat in public, treating the complaints as hypothetical scenarios: so-called ‘assumed facts’. The assumed facts enabled legal argument to proceed while protecting government secrecy. It determined in two key cases that the hypothetical practices complained of were lawful; but only because the government disclosed policies and codes of conduct previously held ‘below the waterline’ of secrecy. The disclosures served to make previously unforeseeable practices ‘foreseeable’, and thus lawful. The pattern reveals an implicitly-assumed capacity of administrative law to serve as a publicity device, presumed to communicate something to the public. This, paradoxically, suggests that the extremely detailed Investigatory Powers Act 2016 does not enhance transparency; it protects secrecy.