"He never complained, he didn't stop fighting right until the end," Mr Haslam's mother, Lucy, told Fairfax Media's Northern Daily Leader.

Mr Haslam was 25. He died on Tuesday afternoon, five years after first being diagnosed with terminal bowel cancer.

Mr Baird, who credited meeting Mr Haslam with a change in his views on medicinal cannabis, said he was deeply saddened by his death.

"I will never forget the look in his eyes the first time I met him and it will stay with me forever," the Premier said in a statement. "Dan made a lasting impression on everyone he met, but, more than that, he left a legacy in NSW that will be felt across the nation, and I believe the world.

"Every step we take on medical cannabis will be built on the footsteps he left behind."

Mr Baird announced in December plans for a clinical trial of medical marijuana for a range of conditions, including end-of-life pain, intractable epilepsy and the chemotherapy-related nausea for which Mr Haslam first sought treatment.

Mr Haslam was an unlikely advocate for the drug. His father, Lou, was a former drug squad detective.

He and his mother began researching cannabis' medical applications after he was diagnosed with terminal bowel cancer at the age of 20.

After the cancer spread to his liver and later his bones, Mr Haslam felt severely depleted by a barrage of aggressive chemotherapy treatments he underwent in Europe and Australia. He would vomit not just after undergoing chemo, but at the mere thought of it.

Adding to his pain were the side-effects of high-grade opiate painkillers – and the concomitant withdrawals.

It was then that a fellow cancer patient suggested he try using a cannabis tincture in tandem with chemotherapy treatments.

"My immediate reaction was 'no way'. Dad was the head of the Tamworth drug squad in the police force and I'd grown up in a very straight-edged family," Mr Haslam said.

He also recalled singeing his stubble with his first marijuana cigarette. But the relief was instant and palpable.

"The difference in how I felt was amazing; it can't be understated," he said. He credited the drug - which he preferred to use in the form of cannabis oil - with allowing him to eat while completely overturning his nausea.

After seeing her son's dramatic results, Mrs Haslam began a campaign to legalise the medicinal use of the drug.

It drew support from a range of eminent Australians, including the former head of the AFP, Mick Palmer, and Nationals MP Barnaby Joyce.

By July, the family had secured a one-hour meeting with the state's Premier in Sydney.

Mr Baird announced guidelines for the new clinical trial last December.