Ms Caldwell has accused Home Office Minister Nick Hurd of having “likely signed my son’s death warrant” following the seizure.
He recommended she take her son to one of three specialist consultants but her requests have not been accommodated.
The Health Department in Northern Ireland said it had been in “repeated contact” with the Home Office to explore possible ways forward in respect of patients seeking access to cannabis-related medicines.
It said: “Our officials are naturally keen to be sensitive and understanding towards parents campaigning on this issue.
“Clearly, the Department has to comply with the law – and advise colleagues in health and social care to do likewise.
“That would include advising any doctors that prescriptions cannot be written for defined cannabis-containing products without a government licence.”
Ms Caldwell said the case was escalating into the medical version of the Windrush controversy, which saw the resignation of former Home Secretary Amber Rudd over immigration