Justice Palmer said the Supreme Court ruled that Cameron's knowledge of dealing controlled substances constituted "recklessness".
"That is why the Supreme Court ordered a retrial," Justice Palmer said.
"You knew, or at least were reckless, about if the substance was a controlled drug."
Cameron was a party to importing 254.8 kilograms of powders containing 4-MEC, enough to press 1,274,000 4-MEC pills.
He was also involved in the sale of 1,244,000 4-MEC pills with a street-value of $49,760,000.
"Your role included introducing a major distributor," Justice Palmer said.
"It also included indirect assistance and encouragement of the broader offending of the London Underground."
Cameron had been involved as a wholesale customer, had introduced associates to London Underground, and received packages and commission on pills sold.
When the business was approached by a gang, Cameron had arranged a payment of $10,000 for the gang to leave them alone.
Defence lawyer Greg Morison said the distinction of "reckless" versus "actual" knowledge, in addition to Cameron's personal circumstances, should warrant an increased sentence discount.
"It is my submission Cameron was no more than reckless," he said.
"He was not directly involved in the day-to-day running of London Underground.
"He was a significant customer, but did not play a hands-on role in the supply of pills.
"He made introductions and left individuals to deal directly with each other."
Morison said Cameron had relied on advice from others about the legality of the pills.
Cameron accepted he was reckless, and with all of the signs should have made more enquiries and sought his own legal and scientific advice.
"And he forever regrets he didn't do that now."
Since he was released on bail last year Cameron had been "proactive", Morison said.
"In the seven to eight months he has been on bail ... he has got married, his wife is expecting a child, and he has taken a job as project manager at a roofing company."
Cameron was not a consumer of drugs or alcohol, and lived an "extremely wholesome and fit lifestyle", Morison said.
During his time in prison he had reflected on the harm of his actions to the community, had a "lasting impact" on staff and fellow prisoners.
"It is hard to think what more he could have down in the time he was incarcerated."
Cameron was due to appear before the parole board in September, but decided to still appeal his sentence, a decision he was "extremely troubled with", Morison said.
Morison requested Justice Palmer to consider an alternative to imprisonment, given the "unusual situation".
Justice Palmer said although Cameron had been reckless, he knew of a search and seizure of 4-MEC pills by police in 2010, the arrest and charge of a major distributor, and despite that still facilitated London Underground.
He also avoided conducting pill sales in public, and sold pill sales only for cash and had no accounting record.
Justice Palmer set a sentencing starting point at eight years.
He said Cameron's personal circumstances and actions while in prison "suggest genuine remorse and genuine effort".
"At 42, I agree there is a real prospect of getting your life back on track."
Justice Palmer took a discount of 18 months for these circumstances, and a further 11 months for an early guilty plea.
He sentenced Cameron to five years and seven months' imprisonment for each of the four charges, to be served concurrently.
