Subsection (1) provides that the functions mentioned in subsection (2) shall, so far as they are exercisable within devolved competence, be exercisable by the Scottish Ministers instead of by a Minister of the Crown.
This subsection has the effect of automatically transferring the functions from a Minister of the Crown to the Scottish Ministers but only “so far as they are exercisable within devolved competence”. To the extent that the function is exercisable outside devolved competence, then it is not transferred and remains with the Minister of the Crown. What devolved competence means is defined in section 54.
However, a function can only transfer if it is separately exercisable within devolved competence and section 106 may be used to facilitate its transfer by making it separately exercisable.
Sections 56 and 57(1) make provision for certain functions to continue to be exercisable by a Minister of the Crown as well as by the Scottish Ministers.
Subsection (2) defines the functions which may be transferred as being:
but not the retained functions of the Lord Advocate as defined in section 52(6).
The “prerogative and other executive functions exercisable by Ministers on behalf of Her Majesty” would include any non-statutory functions which are exercisable by a Minister of the Crown. These functions are not confined to functions which were possessed by a Minister of the Crown when section 53 was commenced on 1 July 1999. They would include functions acquired thereafter by a Minister of the Crown so far as they are exercisable within devolved competence, such as the function of implementing any new EC or international obligation relating to a devolved matter.
The “functions conferred on a Minister of the Crown by a prerogative instrument” are also not time limited and would therefore include any function conferred upon a Minister of the Crown by a Royal Charter made under the prerogative after 1 July 1999. “Prerogative instrument” is defined in section 126(1).
The statutory functions which are transferred are limited to functions conferred on a Minister of the Crown by any “pre‑commencement enactment” which is defined in subsection (3). However a Westminster enactment which is passed after devolution may contain a provision which deems it or certain provisions in it to be a pre-commencement enactment. This would then enable functions conferred by that enactment upon a Minister of the Crown to transfer to Scottish Ministers under section 53 “so far as they are exercisable within devolved competence”.
Subsection (3) defines a “pre-commencement enactment” for the purposes of the Act as:
Subsection (4) draws attention to the fact that this section and section 54 are modified by Part III of Schedule 4.  That modifies the general effect of the devolved competence test for certain enactments and other aspects of the law which that Schedule protects from modification by the Scottish Parliament.  Paragraph 12 of the Schedule has the effect that, in general, Ministerial functions conferred by such enactments which are protected from modification are not transferred.  However, paragraph 13 provides for some exceptions to that in relation to, for example, the European Communities Act 1972 and the Human Rights Act 1998, so that certain Ministerial functions under those Acts are transferred to the Scottish Ministers.
Commentary Part II: the Scottish Administration Details of Provisions