Yeah, me too - hard pill to swallow. But if I'm not mistaken, a zero balance means that at this time his account can cover the margined shares. If some of his collateral depreciates, his margin account will need to make up the balance of cash needed to maintain the shares. If a person is unable to scratch up the nessary cash, the broker sells some of the margined shares to rebalance the account, and the client has no say so on that either. So, while it may seem that the shares on margin are owned, they are really not, thus the term margin. This is in no way fact but just how I recall it when I traded on margin years ago - don't anymore. Maybe someone that is more knowledgable on margin accounts can chime in. What I remember most about margin is that it was great if the stock was going up, hell if going down. As far as the legal ownership, not sure.