17 CFR 31.20 - Prohibition of guarantees against loss.
(a) No leverage transaction merchant shall in any way represent that it will, with respect to any leverage contract in any account carried by the leverage transaction merchant for or on behalf of any person:
(1) Guarantee such person against loss;
(2) Limit the loss of such person; or
(3) Not call for or attempt to collect initial, minimum or maintenance leverage margin established for customers.
(d) This section shall not affect any guarantee entered into prior to the effective date of this section, but this section shall apply to any extension, modification or renewal thereof entered into after such date.