A federal court in Seattle has permanently barred a prison inmate from promoting a tax avoidance scheme that attracted over 44,000 customers and earned over $50 million.

The Justice Department said that Daniel Andersen, founding member of the Institute for Global Prosperity, has been permanently enjoined from promoting the scheme. Andersen and co-founder David Struckman started the institute in 1996.

The group charged customers $1,250 for a 12-part audio course that explained various theories about why they did not have to pay federal income taxes. The government labeled the theories “nonsense.”

Andersen is currently in federal prison in Lompoc, Calif., in connection with his promotion of the scheme. Other tax avoidance promoters sold their schemes at conferences organized by Global Prosperity. Many of these vendors have also been sentenced to prison for federal tax crimes. Global Prosperity charged as much as $37,000 to attend such conferences, according to the Justice Department.