It's your money, you can withdraw as much as you want. There is no legal requirement that you keep any minimum amount in an account. Of course, the bank may have a minimum balance requirement to avoid a fee, but that's the bank's rule, not a law. And if you take your account down to zero, the ban may close the account after a pre-defined period of time. At the end of the day, it's your money, not the bank's.