She later sentenced him to 5 years and 2 months in prison.
Now 60, and in remission for prostate cancer, McKelvy appealed the length of the sentence.
His lawyer, Murray Gibson, argued the starting point was "manifestly excessive" and the discounts for ill health and his guilty plea were too small.
"We disagree," wrote the Court of Appeal in dismissing the application. The starting point of six years for the sentence was within an appropriate range, as was the discount for the guilty plea.
Although he pleaded guilty, McKelvy still took the case to a disputed facts hearing - arguing the GBL was a cleaning agent - which the Court of Appeal said was akin to a trial.
While the discount for his ill health could have been more generous, the Court of Appeal said it was within the range, and the total discount of 10 months was "not inadequate".
This is McKelvy's second stint in prison.
In 2004, McKelvy was arrested after a long-running investigation codenamed Operation Allsorts that led to more than 25 people being convicted for their parts in scams totalling $6.4m.
He was the "chief executive" of a group that included crooked lawyers, accountants and property valuers, using his position as a mortgage broker in Hamilton to attract and identify potential victims.
Described as "predatory" by Justice Paul Heath, McKelvy was jailed for eight years in 2006 after admitting 27 dishonesty charges.
He sat then at the pinnacle of a sophisticated mortgage ramping scheme which scammed millions of dollars from vulnerable low-income home buyers.
One was an elderly widow suffering from cancer, one of many who lost their homes because of the "insidious" scheme orchestrated by McKelvy, a Hamilton mortgage broker at the time.
One of McKelvy's schemes involved lending money to lower-income families in return for them signing over their homes into what they believed was a family trust.
McKelvy then raised mortgages against the homes without telling the owners.
In total, he was individually responsible for ripping off $1.4m.
Justice Heath described the fraud as "predatory", "insidious", "recidivist" and "amoral".
"You preyed on the ill, the elderly and the commercially naive. In one case you defrauded a widow of her home, notwithstanding the fact that you knew the family and she was ill with cancer at the time," said Justice Heath.
"They are the stories of some, but by no means all, of your victims ... they do provide an insight into the level of amoral conduct to which you were prepared to sink in order to gain financial benefits for yourself."
McKelvy was bankrupted for the second time after Operation Allsorts and Justice Heath denied his application to be discharged in 2010.
In refusing to discharge McKelvy, Justice Heath described his conduct as "predatory" and "primarily designed to relieve truly vulnerable members of society of what little assets they had".
"The appalling and amoral conduct in which Mr McKelvy engaged is, in itself, a good reason not to allow him to be discharged from bankruptcy at this stage."
He was released in 2010 and three years ago he was discharged from bankruptcy - for the second time - despite a judge finding McKelvy "remains a genuine risk to the community".
By then, McKelvy had moved to Auckland and was "well regarded" by his employer in machine maintenance.
However, he became a suspect in Operation Leopard after the Customs Service seized six importations of GBL between October 2014 and January 2015.
The total of 81L was worth around $354,000, while another four shipments of unknown quantity slipped through.
When stopped by Customs at the airport and interviewed, McKelvy explained he imported the product as a cleaning agent and co-operated with investigators.
He maintained this explanation in the disputed facts hearing in front of Judge Moala, giving evidence the cleaning chemicals used at Envirowaste, where he worked, were toxic and burned skin.
So he searched online to find a safer product and in a trial test successfully cleaned a truck without wearing any protective gear. McKelvy said he didn't realise the "wonder cleaning" product contained GBL.
His innocent explanation was completely rejected by Judge Moala in favour of the other evidence.
"It is a weak attempt to legitimise what was clearly an illegal importation of GBL," she wrote.
Emails and text messages made it clear McKelvy was discussing GBL, without any mention of an industrial cleaning agent.
In fact, in some correspondence McKelvy asked for the GBL labels to be removed from the plastic containers.
"There is overwhelming evidence that he knew it was GBL, and that it was illegal to bring it into New Zealand," said the judge.
"He knew he had to disguise it so that it can get through Customs."
Judge Moala also described as "ludicrous" McKelvy's evidence the product he imported was safer than the cleaning agents used at Envirowaste.
"The expert evidence is that GBL is a hazardous and toxic substance that can cause serious harm to anyone who uses it without protective gear.
"It is my view that Mr McKelvy used his employment with Envirowaste as a convenient cover for his illegal importation of GBL.
"The financial gain from GBL is not its use as a cleaning product but from selling as a recreational drug."
A chequered past
1995: Placed into bankruptcy.
1996: Convicted of dishonesty offences.
1998: Convicted of dishonesty offences.
2001: Gives evidence in Serious Fraud Office trial against co-accused.
2004: One of more than 30 people charged in Operation Allsorts, a large fraud investigation. Bankrupted for second time.
2006: Convicted on 27 charges and sentenced to eight years in prison.
2010: Released by Parole Board. Application to be discharged from bankruptcy denied.
2014: Discharged from bankruptcy with strict conditions.
2015: Charged with importing Class-B drug GBL, or Fantasy. Pleads guilty to two representative charges.
2017: Sentenced to 5 years and 2 months in prison.
2018: Court of Appeal rejects his appeal.
