Domestic intelligence operates just like the police do.  Domestic intelligence does require the collection of information, but this is not fundamentally different from a standard police investigation. The differences are minor when we have national security at stake. Furthermore, the rights, duties and powers of a domestic intelligence service are carefully restricted by law. For example, under Dutch law, the General Intelligence and Security Service (AIVD) is only allowed to wiretap someone after permission granted by the Minister of Interior Affairs (the UK situation is very similar). [1] Generally speaking, for every surveillance action the domestic intelligence can take, it needs to weigh whether the action satisfies the principles of proportionality and subsidiarity, meaning that the invasiveness of a surveillance method should be proportional to the risk the person poses, and that the method chosen should be the least invasive of all possible methods.  [1] van Voorhout, Jill E.B. Coster, ‘Intelligence as legal evidence’, Utrecht Law Review, Vol. 2 Issue 2, December 2006,  , p.124