Mitchell used to be a customer of Primenet, an Internet Service Provider based in Phoenix, that was my employer. He named us in one of his lawsuits, along with numerous other ISPs, on the grounds that one of our users had the temerity to put a link on his web page to a copy of Mitchell's "The Federal Zone: Cracking the Code of Internal Revenue." Mitchell insisted that he didn't authorize that copy of his work, and that our user's link constituted contributory infringement of his copyright. When I pointed out that the link was actually a dead link and didn't point to anything at all, this did not persuade him that Primenet shouldn't be sued. He never bothered to properly serve Primenet with papers, and the case was thrown out of court.
Mitchell is or was also a member of the "Scholars for 9/11 Truth" organization; I've previously written more about Mitchell and that organization on this blog.