Despite the incredibly broad powers granted to the police by the infamous section 7 of the Terrorism Act 2000, British police seem to have managed to overstepped their authority in detaining David Miranda. They don’t need any reasonable suspicion of anything, but their actions may only be directed toward determining whether the person is a terrorist.
I’m no legal expert, but I looked at the official text of the law, and found that the paragraph of the infamous schedule 7 on “power to stop, question, and detain” begins by confining the power to a single purpose
An examining officer may question a person to whom this paragraph applies for the purpose of determining whether he appears to be a person falling within section 40(1)(b).
That paragraph, defining the people subject to detention under this act:
40 1) In this Part “terrorist” means a person who—
(b)is or has been concerned in the commission, preparation or instigation of acts of terrorism.
And yet, reports on the questioning of David Miranda say that they were not directed at linking him to any acts of terrorism, past or future:
The questions, [Miranda] said, were relentless – about Greenwald, Snowden, Poitras and a host of other apparently random subjects.
“They even asked me about the protests in Brazil, why people were unhappy and who I knew in the government,” said Miranda.
Note that the law seems (to the untrained eye) extremely specific about the permissible purpose of the detention and questioning. It is only for the purpose of determining if the person is a terrorist. Will the lawbreakers be brought to justice? Do we have to ask?
[Update 20 August, 4:30 pm] Joshua Foust has argued that, while the UK interrogation of David Miranda was regrettably extensive, they were probably legal under the Terrorism Act. I think he is confused here (though certainly I may be the one who is confused) about the distinction between the right of the police to detain someone. According to the Act,
An examining officer may exercise his powers under this paragraph whether or not he has grounds for suspecting that a person falls within section 40(1)(b).
So there is no question that they had the right to detain him, since they have the right to detain anyone at all. What is at issue is their goal, as expressed in their actions during the interrogation. So, while they don’t need any reason to think the person is a terrorist, in fact don’t even need to think that they are, and could interrogate people chosen at random, they can only do so, as stated in the section of the Act quoted above, “for the purpose of determining whether he appears to be” a terrorist. Foust suggests that threatening to expose GCHQ could count as terrorism, under the portion of the definition that includes activity that “is designed seriously to interfere with or seriously to disrupt an electronic system.” That sounds pretty far-fetched to me, but it is in keeping with the pattern that we have seen, where security officials demand sweeping powers, codified in vaguely formulated laws, and then proceed to push the boundaries of even those laws and reinterpret them (secretly) beyond all recognition.
It’s a bit like firing an employee in the US: You don’t have to have any reason, but you can’t have an illegal reason. It can be because you have indigestion, or because an angel told you to fire her, or because she’s too beautiful, but it can’t be because her skin colour clashes with your wallpaper or she’s pregnant or is in a wheelchair. And evidence for your illegal reasons are not just your explanation of the firing (or lack thereof) but other comments and actions surrounding it.