The judges and juries in court, that's who.
The man was told not to give advice, he wasn't prosecuted! If he was guilty of something where is his conviction?
Most of the tax gurus pushing this stuff do NOT practice it.
And if he continues to give advice in return for money, he can be prosecuted for defrauding his customers.
But the usual pattern is as follows:
Tax guru sells materials to taxpayer.
Taxpayer applies the material and doesn't pay taxes.
IRS does its stuff. Eventually, there is a notice of seizure.
If the amount of taxes owed is sufficiently egregious, taxpayer gets prosecuted. If he has a good lawyer (which is rare), he uses the Cheek defense and gets acquitted on the criminal charges. Usually, he doesn't and gets sent to jail.
BTW, the tax guru never shows up or returns the frantic calls of the taxpayer.