A bank can own BTC.  A bank can sell BTC.  There is no obligation to adhere to the same regulations that apply to fiat aside from what is already established for you and I just because it is a bank.  A bank can buy and sell cars, snow cones, or goats if they want (and often do in the case of recovered collateral).  There is no way to stop banks from entering BTC.  If we can say BTC cannot be owned by entity X, then the same can be said for person Y.