i think the example i used in the past was mind-control ray guns from aliens.

let's say the president decides she wants to pass a law that says that everybody has to wear tinfoil hats, to protect us from alien  russian mind-control weapons. i think we can all intuitively understand that this ought to be unconstitutional. but, how do you win the case?

a naive response may be to argue against the premise: you're going to want to prove in court, somehow, that there aren't really russian mind-control weapons. and, you will no doubt be flabbergasted when you lose, as the court really has no ability to interpret national security documents, or otherwise create presidential policy. if the president thinks there are russian mind-control weapons and we need to be protected from them, that is his prerogative.

if you want to actually win the case, you have to start by conceding the point and rather make an argument that there is no evidence that tinfoil hats are effective in shielding against russian mind-control weapons.

it's a function of the separation of powers. and, as crazy as it seems, there's a reason that the president is the president, and the supreme court isn't. courts simply don't have executive power.