story
I am not a lawyer and I am in no way familiar with UK law, but my reading of the law is given below:
tdlr; Section 7 applies people that the officer wishes to determine are terrorists defined in Section 40(1)(b)[1]. It does not require evidence, but the purpose is to determine if the person is, in fact, a terrorist.
[1]: http://www.legislation.gov.uk/ukpga/2000/11/section/40
Section 7 states: "For the purpose of satisfying himself whether there are any persons whom he may wish to question under paragraph 2 an examining officer may—"
Paragraph 2 states: "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)."
Section 40(1) (b) states: "In this Part “terrorist” means a person who— (a)has committed an offence under any of sections 11, 12, 15 to 18, 54 and 56 to 63, or (b)is or has been concerned in the commission, preparation or instigation of acts of terrorism."
If you were to have concern about the JA incident your primary argument should be with the seizure of assets not with the detention and questioning.
The presumed search of material on JA and his partner are the only issue that is not within the norm in the US, but is actively being deliberated about in the courts. The act of searching a cell phone specifically while you are detaining someone for questioning is being actively challenged in the court system.
In reference to schedule 7, the questioning of a concerned party within a specific context that is being used in the commision of crime is commonplace in most if not all policed states. For example a comparison would be the detention and questioning of Target IT department following the breach of their system last year. They are not a suspect but are directly concerned with the commision of that crime.
