(1) Where it appears to the Attorney General at any time that the circumstances surrounding the issue of a warrant have changed after the duty to issue has arisen under section 3, and as a result of the change, the transfer becomes inappropriate, the Attorney General may, where the warrant has—
(a) not been issued, not issue the warrant; or
(b) been issued, revoke the warrant in the form prescribed in Form 4 of the Schedule.
(2) The Attorney General may also vary a warrant to give effect to a repatriation agreement.
(3) Where a warrant is to be varied, the Attorney General may issue a new warrant under this Act containing a provision superseding some or all the provisions of the previous warrant.