Legislation controlling power existing independently of statute
37.A third general reason for legislation relating to departments might be to control or limit the powers which they would otherwise have under the common law. (If the matter is the limiting or controlling of powers conferred by statute that limit or control would usually be by way of the very statute which confers the power: consider for instance a power of inspection.) So the very broad power which we all have - one which the executive has as well - to gather, assemble, and transmit information about individuals might be limited so far as the State is concerned. The Security Intelligence Service legislation does that for that particular service. It does not however impose such a limit on other departments. To be fully effective in respect of the whole of the executive, such legislation would have to apply generally across the public service, and the Information Authority has indeed made proposals to that effect. (Collection and Use of Personal Information 1988 App JHR E 27B).
38. We should stress again that this report is about the regular department, its relations with its Ministers and the regular run of functions and powers. So it is not about the position of officials who, or public bodies which, are to have functions independent from Ministers. Such functions and relations do require different legislative treatment, for instance in terms of any power of the Minister to give directions to the official or body (see Legislative Change, paras 101-104).