One more thought on l’affaire Miranda that hasn’t, I think, been sufficiently represented in the public discussion: What is stolen information? If David Miranda had picked up the British crown jewels in Berlin, and was flying them to Brazil, and was foolish enough to change planes in Heathrow, of course the police would have every right to stop him there and confiscate the jewels.
In fact, though, Miranda was carrying information. If his memory was good enough — if he had a photographic memory — he could have carried it in his head. He is a Brazilian citizen who has, so far as I know, no connection to the UK. What possible justification could there be for expecting him to keep British secrets? If we consider the implications of countries stopping travellers in transit, to examine and confiscate the information they are carrying, it is chilling. And again, what if the traveller is carrying the forbidden information in his head rather than on a hard drive? I’m sure I know many things which whose distribution could benefit enemies of, say, the Iranian state, or the Chinese.