"Our challenge isn't so much to any specific act of the intelligence services, our challenge is to the legislation which governs what they do," Carey said, adding that it would have been pointless to go to the Investigatory Powers Tribunal.
Because the Tribunal is completely secret, it also wouldn't have been practical to bring the case there, Carey said. "One has no right to appeal, one isn't even been told if there is going to be a hearing in your own case. It is not effective even if one was to have a complaint that fell within its jurisdiction," he said.
So far the campaigners have been funding their challenge with £27,279 (US$45,340) raised through crowd funding. This has covered the first stage of the legal challenge and helped develop and maintain the group's website privacynotprism.org.uk. For the next stage, the groups hope to raise £40,000 to cover legal costs.
Sign up for CIO Asia eNewsletters.