"Can't" in the sense of "This can't be happening".
On second thought, I think it might be better to say something I used to hear when I was a kid and asked to do something I wouldn't be allowed to do.
Трамп? Нет, невозможно!
IIRC, that's roughly "No, not permitted." Or even simpler, ...
Трамп? Нет!
bcnu,
Mikem
Social Media is for Sociopaths.