The European Commission recently sent a Statement of Objections to Google, alleging it violated European Union antitrust rules by systematically favoring its own comparison-shopping product over others’. The charge, however, may be difficult to prove in court.

According to The New York Times, “any harm that Google’s practice has caused competitors may be hard to quantify because Internet retailing remains very competitive.” For example, shopping giants like Amazon and eBay could also have an impact on these companies’ business.

Per The Times, Google has contested the allegation and has 10 weeks to respond. If the response is not satisfactory, the European Commission could fine the company up to 10 percent of its global revenue, equaling about $6.6 billion. Google can then appeal the decision in court.

The Times raises another point about the case against Google: consumers’ use of shopping site apps over Internet searches. Since technology use is changing rapidly, “proving that a practice is harming consumers can be very difficult.”