Meta Platforms lost its legal challenge after the Luxembourg-based General Court sustained the European Commission's view that Messenger is a powerful gatekeeper for businesses seeking users.
The ruling means Messenger meets thresholds that trigger obligations under the Digital Markets Act, the EU law that became applicable in 2023 to curb the influence of a handful of large tech platforms.
"The Commission did not err in finding that Messenger individually is an important gateway," the judges said.
The court annulled the Commission's designation of Meta's Marketplace platform, finding the regulator had not adequately explained its reasoning.
That decision is largely academic because the Commission dropped the gatekeeper label for Marketplace last year after the service fell below the user threshold.
Meta said it welcomed the court's judgment on Marketplace, that it was reviewing the Messenger finding, and that it would consider its options.
The ruling can be appealed to the Court of Justice of the European Union in the case T-1078/23 Meta Platform v Commission.
