If one is expelled from Hogwarts, one is forbidden from practising further magic altogether.
It doesn’t seem too implausible for them to have a law saying something along the lines of “a person who has been expelled from one magical school may not be admitted to any other magical school”.
It doesn’t seem too implausible for them to have a law saying something along the lines of “a person who has been expelled from one magical school may not be admitted to any other magical school”.