France’s antitrust board has fined Google €150 million ($166 million) for abusing its dominant position in the online search advertising market.

In its decision published online, the board said that Google Ads, the advertising platform of The Alphabet unit, imposed rules on advertisers that were established and applied in conditions that were “non-objective, non-transparent and discriminatory.”

The French regulator said Google Ads’ “opaque and hardly understandable rules made it difficult for advertisers to understand and follow, whereas Google was free to decide to modify the interpretation of rules in a hardly predictable way, and consequently decide if the advertising website respected them or not.” The antitrust board demanded that Google “clarify the rules of operation of Google Ads, as well as the procedure of suspension of accounts.” Google will also have to put in place “measures of prevention, detection and handling of violations of Google Ads’ rules.”

The antitrust board’s investigation into the online ad sector kicked off years ago after a complaint filed by a company called Gibmedia, whose Google Ads account was closed by Google without notice.

In a statement given to Techcrunch, a spokesperson for Google said that the company had good reason to suspend Gibmedia. The statement said Gibmedia had been “running ads for websites that deceived people into paying for services on unclear billing terms….We do not want these kinds of ads on our systems, so we suspended Gibmedia and gave up advertising revenue to protect consumers from harm.”

Google’s statement added: “People expect to be protected from exploitative and abusive ads and this is what our advertising policies are for.”

Google has now been hit with billions of dollars in fines by antitrust regulators around Europe over the past two years, including, chiefly, the E.U.’s antitrust authority.

Earlier this year, European Commission slapped Google with a €1.49 billion fine for breaching E.U. rules by preventing rivals from placing their search advertisements on third-party websites, and for imposing restrictive clauses in contracts with third-party websites.

When it handed out its decision, the European Commission said that while market dominance was not illegal under E.U. antitrust rules, “dominant companies have a special responsibility not to abuse their powerful market position by restricting competition, either in the market where they are dominant or in separate markets.”