The US Federal Trade Commission is continuing its efforts to block Microsoft’s Activision Blizzard purchase — despite it being a done deal.

The EU and UK both signed off on Microsoft’s acquisition after the company made concessions to address concerns. The FTC has remained opposed to the deal, despite setbacks in court.

According to Reuters, the FTC is appealing the decision by a lower court that ruled the agency had not made its case that the Microsoft/Activision deal would harm consumers.

According to two antitrust experts that spoke with the outlet, the FTC has an uphill battle to win the appeal. The judge who ruled in favor of Microsoft did so after reviewing “a huge amount of record evidence,” and it will be difficult to prove the judge made a “clear error.”