Britain's Home Office used a special power on Saturday to return medicinal cannabis oil that had been confiscated from an epileptic boy.
Billy Caldwell, 12, travelled to Canada with his mother to get the oil after his doctor was told to stop prescribing it.
It was taken off them when they flew back into London on Monday.
Caldwell was hospitalised on Friday suffering from several seizures.
His case stirred debate surrounding the medicinal use of cannabis, with campaigners calling for it to be legalised.
"This morning, I've used an exceptional power as Home Secretary to urgently issue a licence to allow Billy Caldwell to be treated with cannabis oil," Sajid Javid said in a statement.
"My decision is based on the advice of senior clinicians who have made clear this is a medical emergency."
Charlotte Caldwell, Billy's mother, said the child was free of seizures when he was using the cannabis oil.
She made a statement to reporters outside Chelsea and Westminster Hospital, where her son was being treated, calling for the law to be changed.
"No other family should have to go through this sort of ordeal, travelling halfway around the world to get medication which should be freely available to our desperately ill children," she said.
"This is a wake-up call for our country. In the 21st century, we need to have a more humane policy, not panic measures. I hope the government reflects upon what happened and what they've put our family through these last few days."
Politicians from different parties backed the family and campaigners in their demand for change in the law.
The Home Office previously said it sympathised with Caldwell's situation but it had a duty to stop banned substances from entering the country.
Under British law, cannabis is listed as a schedule 1 drug, meaning that it is not recognised as having a therapeutic value.