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An internal investigation had been carried out and the Edinburgh flanker will miss three months, backdated to mid-October when his initial suspension began.
He will be available for selection in mid-January at the earliest.
"John has co-operated with the disciplinary process throughout," an Edinburgh spokesperson said.
"He has acknowledged the serious mistake he has made as a professional athlete and has accepted full responsibility for his conduct.
"It has been made clear that we are not prepared to tolerate the behaviour which caused this situation.
"Support will be provided to the player by Edinburgh Rugby and Scottish Rugby on a personal and professional level throughout the period of his suspension and going forward."
Hardie, who played 53 games for the Highlanders between 2010 and 2015, apologised for his actions.
"I would like to apologise to everyone for putting myself in this situation.
"Through my actions I feel I have let my club, my teammates and the fans down. I want to acknowledge the support I have had from Edinburgh Rugby and Scottish Rugby in dealing with the issue.
"I am now focused on putting myself in the best possible position to be considered for selection again."
Originally from Lumsden, Hardie played for Southland between 2007 and 2014.
However, he made the move to Edinburgh after the 2015 Super Rugby season.
Being eligible to represent Scotland, he was fast-tracked into the national side, and played at the 2015 World Cup.
He has since played 16 tests.