A former top aide to Stephen Harper has been found not guilty of influence-peddling.

Bruce Carson was charged in connection with his attempts to promote the sale of water purification systems for First Nations communities by a company that employed his former escort girlfriend.

The Crown argued that Carson tried to use his contacts within the Department of Aboriginal Affairs and the Prime Minister's Office to ensure the company's financial success.

In emails submitted into evidence during the trial, Carson bragged about his ties to Harper and others, saying they would be a boon for the fledgling company.

Carson's lawyer, Patrick McCann, acknowledged during the trial that his client tried to help H2O Pros sell water-treatment equipment to indigenous communities.

But he argued there was nothing in law that prohibited Carson from this sort of lobbying.

Ontario Superior Court Judge Bonnie Warkentin has ruled that while it was clear that Carson was trying to use his influence to benefit his former girlfriend, the Crown failed to show the federal government had a direct say over what kind of water-purification equipment First Nations communities can purchase.

In essence, the judge agreed with the defence that federal officials had no influence over the purchases of the water systems, and therefore Carson's connections in government would have had a negligible effect.

McCann told CBC News today that the Crown "was trying to put a square peg in a round hole," adding that his client was "much relieved and happy" with the decision. 

Carson was a senior adviser to the former prime minister from the time the Conservatives took office in 2006, until he left the post in 2008.

With files from the CBC's Susan Lunn