Unlike countless other 24-year-olds, he doesn't smoke it. If he gets a little high, that is an unwanted side effect.

Dan's father Lou is a former drug squad detective and his mother Lucy is a retired nurse. They started scoring their son's pot for him last year, driven to this criminal enterprise by love and three heartbreaking years of watching the devastating effects of chemotherapy after Dan was diagnosed with terminal bowel cancer in February 2010.

There was nausea, vomiting, chronic weight loss, depression and a tortuous withdrawal from prescribed opioids that made him suicidal. All of that stopped when he switched to his illegal cannabis supply.

"Our local police superintendent came out very early and said he had better things to do than lock up sick people," Lucy Haslam says from her home in Tamworth.

Now her son has become the poster boy for the legalisation of medical cannabis in a campaign that has won the support of politicians of every hue, all the way to Prime Minister Tony Abbott.

This crusade is not new. While medical cannabis is allowed in more than 20 other countries and 20 US states – for treatment of pain, terminal illnesses, multiple sclerosis, epilepsy, seizures and many more conditions – it has met brick walls in Australia.

Former premier Bob Carr attempted in 2003 to establish a four-year medical trial, moved by the suffering of HIV-positive Paul O'Grady, then a state MP. Carr's government conceded defeat the next year, unable to negotiate a minefield of state and federal laws and unwilling to legalise backyard cultivation, even if only for the terminally ill. The hardest question has always been the supply of the drug.

"So it all went in the too-hard basket," says Kevin Anderson, the state Nationals MP for Tamworth who has been swayed by the plight of his constituents, the Haslams, as has Premier Mike Baird.

In July ACT Greens Minister Shane Rattenbury introduced a bill into the Legislative Assembly which would allow terminally and chronically ill people in Canberra to grow marijuana and use the drug to alleviate pain and symptoms, if they had approval from the ACT Chief Health Officer. The bill will be considered by an Assembly committee, due to report by June 2015.

Rattenbury said last week he would consider feedback from the committee and members of the community about the possible model for allowing the use of medicinal cannabis in the ACT.

This week Baird announced that a working group, including police, would investigate how to establish a clinical trial of medical cannabis for the terminally ill. It might consider the state becoming cultivator and supplier, or it could license a provider, as happened in Tasmania, the world's largest producer of legal opium.

"Or the state of NSW could come to an arrangement with me," says Tony Bower. "I could provide it with my products for free."

Bower's company, Mullaways Medical Cannabis, has been supplying tinctures to the chronically ill, including children suffering seizures, free of charge for six years. NSW Health tests have confirmed his product contains no detectable illegal substance. They are not psycho-active, meaning they will not get anyone stoned.

But Mullaway Man, as Bower is known, may be going back to jail for growing the raw material for his product, the marijuana crop on his property near Crescent Head on the NSW mid north coast. On October 7, he will launch an appeal against his second 12-month sentence for cultivation.

"And I've never supplied cannabis for smoking," he sighs.

Only one legal product – a mouth spray called Sativex, made by the British company GW Pharmaceuticals – is available in Australia, but for one condition only: spasticity caused by multiple sclerosis. Pain-relief trials with this drug are under way in the US, but for now there is no legal alternative – with a reliable, measured dose – for terminal cancer patients such as Dan Haslam.

For Warren Entsch, the federal Nationals MP, the seeds of his campaign to legalise medical cannabis came from a death in his family, an MS sufferer whose only relief from horrific shaking was marijuana. Entsch wants legal treatments for not just the terminally ill, and cites evidence of a dramatic reduction in fits for severely epileptic children.

He was heartened this week by Prime Minister Tony Abbott, who trumped Baird's announcement of a trial by declaring there was no need for further testing if cannabis had already been proved safe in other reliable jurisdictions.

Trials can take years. In the meantime, Baird will formalise the discretion NSW police already exercise not to charge the terminally ill with possession of cannabis. Stronger "guidelines" will direct police not to prosecute them – or their carers, if they obtain the drug – though it falls short of decriminalisation.

This is where Baird has squibbed it, leaving families like the Haslams in legal limbo, say the Greens and Labor's Adam Searle, who was on an all-party upper house committee that unanimously recommended the stronger protection.

"When politicians start directing police operationally as to which law you enforce and which law you won't, and against whom, it's a slippery slope," Searle says.

Lucy Haslam does not name her suppliers, who include "compassion groups". Regardless of any law reform, her son Dan will maintain his regime: vaporiser for the chemotherapy, smoothies for the reputed health benefits, including antioxidants, and "because it's not heated it doesn't make him high", and the oil – just possibly – as a treatment against the cancer.

The evidence is not in, his mother admits. "Clinical human trials are still in their infancy. But if you're terminally ill, you can't wait for trials that may take 10 years to evolve."