The states filed their friend-of-the-court brief in San Jose, California, federal court, where the FTC in July asked a federal judge to bar Meta's acquisition of Los Angeles-based Within.
The states, joined by the District of Columbia and Guam, said the deal threatens to "harm competition in the emerging virtual reality space."
Circuit to revive the states' claims after a U.S. district court judge dismissed the case.
Utah, which also signed the amicus brief, is leading a group of states in an antitrust lawsuit challenging how Google runs its app store.
The case is Federal Trade Commission v. Meta Platforms Inc, U.S. District Court for the Northern District of California, No.