The responsible local authority shall have the functions set out in section 23B in respect of a relevant child.
In subsection (1) " relevant child " means (subject to subsection (3)) a child who—
is not being looked after by any local authority in England or by any local authority in Wales;
was, before last ceasing to be looked after, an eligible child for the purposes of paragraph 19B of Schedule 2; and
is aged sixteen or seventeen.
The Secretary of State may prescribe—
additional categories of relevant children; and
categories of children who are not to be relevant children despite falling within subsection (2).
In subsection (1) the " responsible local authority " is the one which last looked after the child.
If under subsection (3)(a) the Secretary of State prescribes a category of relevant children which includes children who do not fall within subsection (2)(b) (for example, because they were being looked after by a local authority in Scotland), the Secretary of State may in the regulations also provide for which local authority is to be the responsible local authority for those children.