The Supreme Court of Canada has rejected an appeal by a former top adviser to Stephen Harper, upholding Bruce Carson's influence peddling conviction related to the sale of water treatment systems on First Nations reserves.

The ruling means Carson will return to court for sentencing on the charge, which falls under fraud offences and carries a potential prison term of up to five years.

In an 8-1 decision, the majority of justices adopted a broad interpretation of what constitutes "business relating to the government" under the Criminal Code section on influence peddling.

Writing for the majority, Justice Andromache Karakatsanis said business related to government includes all publicly funded transactions where the government could impose or amend terms and conditions that would favour one vendor over another, not just those facilitated under the existing operational structure.

"The offence captures promises to exercise influence to change or expand government programs," the decision reads.

An accused does not need to actually have influence with the government, or succeed in influencing government, to be found guilty of influence peddling, because the law targets anyone "having or pretending to have influence with the government," the judgment reads.

One dissenting view

Carson had demanded a benefit, which was a sales commission for his then-girlfriend who was employed by H20 Professionals Inc., in exchange for helping the company land contracts by leveraging his contacts with government and First Nations officials.

In a dissenting view, Justice Suzanne Côté took a narrow interpretation, arguing that "business related to government" must be related to the actual operational structures in place at that time of the alleged offence. At the point in time, when Carson was assisting H20, the federal government had granted First Nations complete autonomy on the purchase of point-of-use water systems, she noted.

At trial, Bruce Carson was found not guilty of influence peddling for trying to persuade First Nations communities to buy water treatment systems being sold by a company that employed his then-girlfriend. The Ontario Court of Appeal overturned the acquittal, leaving the final say to the country's highest court.

The trial judge found the Criminal Code offence of influence peddling applies narrowly to transactions involving the government, while a majority on the appeals court found the offence has a much broader reach.

Carson did not deny he had influence with the government, or that he demanded a sales commission for his girlfriend Michele McPherson in exchange for helping H20 sell their systems to First Nations bands.

A document filed by Carson's lawyer Patrick McCann with the high court said evidence at trial was "overwhelming" that the department of Indian and Northern Affairs Canada (INAC) had no control over or approval role in the purchase of the water purification systems. The First Nations bands had "complete autonomy" in the use of their funds for those purchases.

"Using one's influence to assist in doing business with entities such as First Nations Bands, charitable institutions, start-up companies and others which receive government funding or subsidies and over which the government has no control, cannot affect the integrity of the government and should not attract prosecution (under the Criminal Code)," the factum concludes.

In a response for the Attorney General of Ontario, lawyer Roger Shallow noted that Carson had arranged meetings between H20 principals and INAC and First Nations officials, and led the company to believe he could get them in front of the "right people" to "push it through."

'Morally blameworthy'

"The appellant's undisputed conduct was intentional, morally blameworthy, and compromised government integrity and the appearance of government integrity, the very type of harm the (Criminal Code) section was intended to prevent," he wrote. "The factual findings made by the trial judge compelled a verdict of guilt."

In 2016, Carson was found guilty on three counts under the Lobbying Act over work he did on a national energy strategy while director of the Canada School of Energy and Environment and later as the vice-chair of the Energy Policy Institute of Canada.

McCann told CBC News those convictions were appealed to the Superior Court, where one of the convictions was overturned. The Crown is seeking leave to appeal that ruling at the high court, but Carson is not participating in their application, he said.

Carson had a history of financial problems and was convicted of fraud in the 1980s and 1990s before he was hired as an adviser to Harper.

He worked closely with Harper from 2006 to early 2009, and wrote a book called, '14 Days: Making the Conservative Movement in Canada,' about the early days of the Conservative government.