This week, the D.C. Circuit considered when a nonparty to a case can nonetheless appeal an order in the case. Answer: almost never.
As the D.C. Circuit explained:
It is a well settled rule that only parties to a lawsuit, or those that properly become parties, may appeal an adverse judgment. This rule does not implicate the jurisdiction of the courts under Article III of the Constitution[,] nor … the sorts of concerns that are ordinarily addressed as a matter of prudential standing. Instead, it is a procedural requirement that appellate courts must address separately from issues of standing or jurisdiction.
No. 22-7082, Broidy Capital Mgt. LLC v. Muzin (Mar. 10, 2023) (Slip Op. 7-8).
True, the term “parties” has some wiggle room. It includes not just originally named parties, but also:
 those who properly become parties through intervention, substitution, or third-party practice; and  those who are not named in the underlying action but are both bound by an adverse order and, through applicable procedural rules, seek relief in the trial court proceedings related to the adverse order.
Id. at 23.
But as applied, the court held that Qatar—the nonparty—had not sought relief by, for example, moving to intervene to challenge the discovery orders that it later sought to appeal. “At a minimum,” Qatar should have moved to intervene “for the limited purpose of appealing.”
Form over substance? You can decide. But moving to intervene, even just to appeal, at least would have told the district court that its decision would be challenged. That can focus the judicial mind.
And regardless, moving is a modest step to avoid a futile appeal.