(1) Proceedings for an offence under this Part (other than an offence under section 19(5) or 22) may not be instituted -
(a) in England and Wales, except by or with the consent of the Attorney General;
(b) in Northern Ireland, except by or with the consent of the Advocate General for Northern Ireland.
(2) Nothing in subsection (1) prevents -
(a) the arrest of a person in respect of an offence under this Part, or
(b) the remand in custody or on bail of a person charged with such an offence.