Schiff literally wrote the book on the IRS. The Federal Mafia was a complete walkthrough of the tax code, proving the IRS ran an illegal operation that collected money through coercion and brute force, regardless that there is no law to back it up.
He fought hard against the IRS, demanding to see these laws, asking for proof that they existed. But instead of answering these simple questions, they dismissed his claims as frivolous.
The IRS attempted to ban The Federal Mafia from print and distribution, citing that it was instructing people to break the law by telling them not to file their taxes. Fortunately this was unsuccessful. However the court completely circumvented the question at hand. Instead of determinging if what he was telling people to do was illegal, the court ruled that telling someone not to do something can not be construed as telling them to break a law.
After the IRS failed to ban the book, they had to silence Schiff any way they could. He attempted to bring in an expert witness Joe Banister, an ex special agent of the criminal division of the IRS, to testify on his behalf. The court would not allow the testimony stating that Banister was no longer an expert because he had resigned.
At the end of this trial, the IRS gave Irwin a substitute tax form, one that had been prepared by the IRS, and ordered him to sign it. Schiff insisted that he would happily sign if they would only show him a law requiring him to. At this time Judge Dawson declared "I will not allow the law in this courtroom", and sentenced Schiff to 13 years in prison. He died in 2016, and was not able to be released to spend his final few days with his family.
If the name Schiff sounds familiar, Irwin was the father of Peter Schiff.
Before he was imprisioned, Irwin put most of his materials online for free including tax information and his books. The site is still maintained and available online: http://www.paynoincometax.com/