Judge Aileen Cannon is asking the Justice Department and Donald Trump co-defendant Walt Nauta to weigh in on the legality of special counsel Jack Smith’s ongoing grand jury activity in Washington, DC, which relates to the obstruction portion of the Mar-a-Lago documents case before her in Florida.
If she has the authority to do so, there’s nothing that an appeals court can do about it. Once a case is dismissed, that’s the end of it.
You can appeal a dismissal just like any other final judgement.