The decision means that Steele will no longer be able to practice law in Illinois, and is likely to be emulated in other US districts.
Steele and, by extension, Prenda Law were part of wide-ranging so-called ‘copyright troll’ operation, in which they threatened individuals who allegedly downloaded adult movies from file-sharing websites.
The group extracted around $6 million in copyright infringement settlements between 2011 and 2014.
During his trial at the US District Court for the District of Minnesota, Steele admitted to creating sham entities to obtain the rights to adult movies and then uploaded them to file-sharing websites such as The Pirate Bay and sued people who downloaded them.
The operators of Prenda Law filmed some of these pornographic movies themselves.
Steele said that the group would file fraudulent copyright infringement lawsuits to uncover information about their targets from ISPs, and then use extortion to extract large settlements at the risk of public embarrassment.
The Illinois Supreme Court ruled that the lawsuits had “no substantial purpose other than to embarrass or burden a third person ... using methods of obtaining evidence that violates the legal rights of such a person”.