SEC Short Sale Rule 201
Adopted on Feb. 24, 2010, under the rule, the execution of short sale orders at or below the current National Best Bid is prohibited. Short selling is only permitted if the price of the security is above the current national best bid. The rule is triggered with a 10 percent decline in one day.
Once triggered, the Short Sale Price Test shall remain in effect until the close of trading on the next trading day.

