Jarrell said customers with open accounts were transferred while those with all cash accounts were not because, "moving the open positions could avoid market disruptions and allow customers to have some sort of choice of what to do with the positions."
"We can't distribute cash because we have to know what the amount of segregated cash held for customers is and verify the claims against that pool of segregated cash," he said.
Legal options are less clear for those who have not just frozen cash, but margin calls, Butler said.
"People can't understand how the new margin is being calculated. Some people say they're getting less than 60 percent transferred, others say they're getting 80 percent," he said.