"When hedge-fund manager William Ackman declared last December that he had bet $1 billion against Herbalife because he believed it to be an illegal pyramid scheme, all too many people thought that it was just a matter of months before the FTC would take action. Such assumptions were clearly wrong, and quite frankly, naïve."
Excellent article explaining why it's so difficult to make the case that an MLM is a pyramid scheme...

https://www.truthinadvertising.org/fight-death/