I have been provided conflicting information on this, but one time I spoke to my broker's margin department, I was told that cash and retirement accounts, they can borrow ONLY with YOUR permission, but in a margin account they can borrow your shares if you have a margin balance. He pointed me to the hypothecation (term he used) agreement on the margin account. Frankly, it appeared he was disappointed when he checked that my account, although a margin account holding a lot of CYDY, had no margin balance.