My only point is that the notion of 'legal' can get very fuzzy when you're talking about an industry with so many private/self-interested entities that rival or exceed intellectual/manpower of the agencies responsible for regulation.
If you want to learn more about the SEC's role or dereliction of duty in the Enron case you could start here: https://www.investopedia.com/updates/enron-scandal-summary/#...
Google could lead you to more evidence, if you wish to explore the hypothesis further...