The SEC regulation has to do with the "piggyback rule" that was last amended in 1991.
Brokerage firms have been using this rule to pass down piggyback shorts as a loophole around the system.
Ameritrade probably has the most short shares to buy back because they probably sold the most short and passed them on to others.
I believe we see a massive run up in September on many OTC stocks and this "no buy rule" is only in place if companies do not become current before the Sept 28'th deadline.
Good luck to all contestants in these 2021 Races.
The Current leader has gone from .0036 to 20 cents and now back at 10 cents!