Apple's (NASDAQ:AAPL) App Tracking Transparency (ATT) tool, which lets iPhone users control which apps track their activity, is reportedly under investigation by French antitrust regulators, according to Reuters.

Some digital advertisers and mobile gaming companies have complained that ATT has made it more expensive to advertise on Apple devices. French regulators are said to be weighing whether the tool is anti-competitive, with a ruling expected as soon as next month. If Apple is found to have violated regulations, it could be forced to shut down ATT in France or face a fine.

Apple describes ATT as a framework that provides users with a tracking authorization request and their tracking status. However, its impact on the mobile ad industry has drawn regulatory attention worldwide.

The French probe comes shortly after Apple clashed with the U.K. government over end-to-end encryption. The U.K. Home Office ordered Apple to create a backdoor allowing access to user cloud data, a request Apple rejected by removing its Advanced Data Protection (ADP) security feature from the U.K.

U.S. officials have also weighed in, with Director of National Intelligence Tulsi Gabbard calling the U.K.'s demand for a security backdoor an egregious violation of U.S. rights. Apple has since confirmed that new U.K. users won't have access to ADP, and current users will eventually need to disable the feature.