Under current rules, a short-seller must locate shares to borrow, which are later replaced with stock bought at a lower price. Some market watchers have been concerned that traders were borrowing the same shares from the same lender over and over, and driving down stock prices.

Under the emergency order, traders will be required to borrow the stock and the lender would then take it out of the market and not allow other traders to use it to satisfy requirements that they've located stock.