so what you are saying in my mind is an issue of standing. The people who lost the case don't have standing to re litigate it. Standing probably isn't the right word because it most accurately applies to eligibility to file a dispute in court in the first place. My point is if such and such district court in say texas rules that the government does have the legal right to proceed, IE a case was brought by a pro trump legal team, with the express intention of losing the case. Is this not a granting that the action is legal and isn't the adminstration able to say look we have the court's imprimatur for our actions?
I get what you're saying and it's somewhat like standing, , Trump would get a decision saying he's right but that decision wouldn't be binding on anyone else. Say I sue a liberal government saying that the 2nd amendment requires them to give me reloading supplies at no cost, while that's about as dumb as most liberal arguments the liberal government would win and I would lose. Since you weren't a party to that first suit you can turn around and sue them for the exact same thing the day after I lose my lawsuit and they would have to fight it out with you just like my suit never occurred. But if I'd gotten lucky and won then they'd have to give you and anyone else who asked free reloading supplies or you could sue them and automatically win based upon the previous ruling against them.
Now I do agree with you that once Trump gets a final ruling on appeal then that would be binding law provided that the opinion was issued on very broad grounds. But that would take years and courts are hesitant to issue broad rulings, most will try to rule as narrowly as possible to prevent unforeseen consequences. Also any 1st year lawstudent with a lap top can think of different reasons why something should be allowed or not allowed, that's one of the reasons the libs file so many lawsuits. Group A files saying the Wall violates their freedom of movement, Group B files in another jurisdiction saying it should be allowed as it hurts endangered species. And then once Trump wins those, Group C will file saying that the wall violate XYZ and on down the line, just every time one suit gets show down another using some different theory would pop up. .
There's no clear cut answer that won't make a bigger problem other than for Trump to appoint and the Senate to nominate conservative judges. Any precedent we set that prevents them for suing over their pet causes would prevent us from suing when we think our rights are being infringed. What if the next Dem president were to be able to file suit against himself in Berkley California and get a ruling that the 2nd Amendment only applies to single shot rifles? If that were allowed to be binding precedent then we're screwed