If a bank tried to pull this ...
Many people who have a Bitcoin position seem to be ignorant to the fact that they aren't insured for even $250. (I've owned Bitcoin since 2011) I suppose they've taken for granted that for pretty much their entire life they've banked and never really thought about the possibility that tomorrow it'll all be gone and it's just SFYL.
You don't own bitcoin if you put them on an exchange. Period.