Filed by the regulator last month following a referral from French controller manufacturer Subsonic, its investigation found that Sony put counterfeiting measures in place in November 2015 that caused third-party controllers to regularly disconnect from the console during system updates.
The competition regulator also found that third-party manufacturers faced difficulty in joining its licensing program, which it alleged that Sony "refused to communicate" terms and criteria to manufacturers who'd requested it.
"The combination of these two practices significantly damaged the brand image of the third-party manufacturers affected," the trade body said, adding: "with regard to both players and distributors, slowing down their expansion in the market and leading to their possible foreclosure."