In the Miranda case because "Reasonable Suspicion" is not needed then the actions were probably within the law. I don't think the same applies to the other case, but we still don't have the CCTV from that although it happened in 2011.
There are many agents of the state that have compulsive powers under the law or can apply for them, the police, border agency staff, the security services, social workers, housing officers etc.
In many cases the underlying intentions may in fact be beneficial to society. Preventing terrorist attacks has to be a top priority for the government. However, the wrongful use of such powers can not only be based on erroneous information or even oppressive by virtue of being disproportionate (and in such in conflict with the original Magna Carta), but also act to undermine society by damaging people's trust in the constitutional settlement.
It is, therefore, important that the law is both proportionate and also followed by public officials. Sadly often this is not the case. Taking out judicial review actions is much like grabbing the tail of a tiger. The threat of legal costs being charged against the applicant often acts to protect misbehaving public authorities. The failure, for instance, of the GMC to investigate the [non fatal] poisoning of babies with Carbon Monoxide in experiments was in my view one of those failures.
The use of secret courts is also something that acts to undermine the requirement for public officials to follow the law. Yesterday, for example, there was a case UQ13C00036 heard in the High Court. It was a very important case for many reasons, but was in secret so we cannot comment in detail about it. In my view the Judge who heard the case was excellent in the way he dealt with the case, but still I am not allowed to go into any details.
This lack of transparency which to be fair the same judge is making some progress in dealing with, does undermine the accountability of public officials. Let us hope that this is not used to shunt the Miranda Judicial Review into a judicial siding.