A spokesperson for the Law Society says Perrin's file was closed on July 14 under one of its rules, which states it can do so "if we are satisfied that the complaint is not valid, or its validity cannot be proved."
The Law Society would not say who or what prompted it to look into the matter, but media reports last November said University of Ottawa law professor and activist Amir Attaran lodged a complaint about Perrin with the society.
In a statement to CBC News, Perrin said, "I am pleased that the Law Society has closed this file and did not find any concerns with my conduct as a lawyer."
He said he looks forward to continuing his work on public policy issues.
Perrin worked as a legal affairs and policy adviser to Prime Minister Stephen Harper in 2012-13.
Perrin's name was cited a number of times in court documents filed by RCMP as part of their investigation into a $90,000 payment to Duffy from Nigel Wright, Harper's former chief of staff, to repay Duffy's ineligible Senate expenses.
The documents said Wright told the investigating officer Perrin was aware of Wright's decision to give Duffy the $90,000, though Wright added Perrin was not involved in that decision in any way.
According to the RCMP, Perrin was also involved in legal negotiations with Duffy's lawyer around the alleged deal, including the conditions under which it would happen and the "media lines" that would be used by Duffy.
There were also concerns Perrin's emails had been deleted after he left his position in the Prime Minister's Office, but the Privy Council Office was subsequently able to retrieve the emails and handed them over to the RCMP.
Since leaving the Prime Minister's Office, Perrin has returned to his position as professor at the University of British Columbia, where he has most recently been working on improving the justice system for victims of crime.