There's a difference between: 1) SEC rules and 2) SEC investigations due to breaking those rules
Here's how it goes: The SEC sets rules and when crooks break them and complaints are filed, the SEC investigates. It's fairly simple, the SEC can explain it to any one who wishes to contact them.
It doesn't change the fact that market manipulation in the form of painting the tape and/or marking the close of a publicly traded stock is illegal.