There is a need to review how cases for the medical use of cannabis are handled, the prime minister has said.
Theresa May made the comment after a special licence was granted allowing Billy Caldwell, 12, to be treated with cannabis oil for his severe epilepsy.
His mother tried to bring the banned substance into the UK last week but it was confiscated at Heathrow Airport.
He has been discharged from a hospital in London, having been admitted on 15 June as his seizures intensified.
Charlotte Caldwell said what her son had endured was “horrendous” after he was left without access to the cannabis oil.
On 16 June, Home Secretary Sajid Javid approved the return of some of the confiscated oil after doctors at the hospital where Billy was being treated at made it clear it was a medical emergency.
Cannabis oil was first used to control Billy Caldwell’s seizures in 2016.
It contains a substance called Tetrahydrocannabinol (THC), which is illegal in the UK but available elsewhere.
Ms Caldwell, from Castlederg in County Tyrone, said it was “vital” for families in the UK to be given “immediate access” to medicinal cannabis in cases where children needed it to treat a health condition.
“The fact that Billy has been discharged and is now with me is testament to the effectiveness of the treatment,” she added.
Ms Caldwell demanded a change in the law, saying that “never again” should someone in her son’s condition “be exposed to Home Office paperwork instead of medical treatment”.
Health Secretary Jeremy Hunt said it was obvious the government was not “getting the law on this kind of thing right” and suggested a review would take place “as quickly as possible”.