As I understand it, Judge Sullivan has a conflict with the executive branch and appointed an attorney to plead his case. But how can one delegate power one doesn’t have? Either the power is delegated and this is a member of the judicial branch challenging the executive branch’s use of its authority or it is not a delegation, in which case it is a random attorney with a general grievance.
If a random attorney at the direction of a judge has standing to challenge actions within executive branch jurisdiction, why didn’t a judge prosecute the banks guilty of criminal fraud leading to the 2008 financial crisis when Obama ordered the DOJ to not prosecute?
Edit: Just realized a third option, that there exists, as in Superman comics, an unelected bizarro executive branch that can be summoned by the judiciary to battle the elected executive branch for supremacy and the one who determines the winner is... the judicial branch.
Edit 2: (In response to people claiming that this is just how things work) Frank v. Gaos affirmed that standing is required at all stages of a case. Courts do not give advisory opinions. Courts do not entertain oral argument between one side that has standing and some arbitrarily selected neutral observer.
Maybe answerers are confused and think that a traditional appeal, where a judge sends it to a higher court has a case and controversy due to a judge wanting the opinion of the higher court rather than the parties themselves having real injury in fact. That is not the reasoning applied by the Supreme Court when it comes to determining standing.
So, I would like someone to reconcile (if possible) the traditional requirements for standing with the facts in the Flynn case before I select an answer.