On Saturday Sajid Javid, the home secretary, announced he had used an exceptional power to urgently issue a license allowing Caldwell to use cannabis oil.
Charlotte Caldwell attempted to bring in medicinal cannabis oil to the United Kingdom for her 12-year-old son Billy but it was confiscated at Heathrow Airport on Monday after a flight from Canada.
Canadian doctors aware of both Billy's condition and the Home Office's "intransigence" have been trying without success to speak with Home Office recommended paediatric consultant Dr David McCormick, who, the family say has so far refused to see Billy.
In 2017, a doctor in Northern Ireland became the first to prescribe cannabis oil on the U.K.'s NHS healthcare service, after it became apparent it was the only treatment which Billy responded to.
Authorities seized it from Charlotte Caldwell, the boy's mother, when she tried to bring it into the country on Monday.
Javid said the government's immediate priority was to make sure the boy received "the most effective treatment possible in a safe way".
"The policing minister met with the family on Monday and since then has been working to reach an urgent solution".
The mother of a boy with severe epilepsy has called for a meeting with the home secretary and health secretary to talk about making medical cannabis legal for children who have similar conditions to her son.
Responding to the home secretary's decision, Caldwell told reporters: "I truly believe that somewhere in the Home Office there's someone with a heart and I truly believe that Billy was pulling on their heart strings".
Charlotte Caldwell says the oil has kept Billy seizure-free for more than 300 days.
Billy started the treatment in 2016 in the U.S., where medical marijuana is legal.
He is still banned from taking the remedy at home but was given the oil at Chelsea and Westminster Hospital under a special 20-day licence.
Billy became the first person in the United Kingdom to receive a prescription after his local GP in Northern Ireland, Brendan O'Hare, began writing scripts.
Ms Caldwell said she was "over the moon" at the release of the medicine but she criticised the "dreadful, horrific, cruel experience" that has deeply affected Billy.
"Billy is in the care of medical professionals who are best placed to assess the care and treatment that he requires".
His case has stirred debate on the therapeutic use of cannabis, with politicians from different parties backing the family and campaigners calling for changes to the law.
"The Home Office is contacting Billy's medical team".
"No other family should have to go through this sort of ordeal, travelling half way round the world to get medication which should be freely available", she said.