He’s just been named the most powerful figure in the music industry (along with his wife Beyoncé), but Jay Z is far from invincible.

The rapper and business mogul has been named as a defendant in a $600 million lawsuit filed by an entrepreneur who claims he trademarked the name ‘Brooklyn Nets’ more than 10 years ago, long before the NBA team – which until last year was part-owned by Jay Z – moved out of New Jersey.

Dr. Francois de Cassagnol filed a complaint in December asking for a trial and $600 million in damages. According to court documents obtained by Radar, de Cassagnol claims that the NBA, Jay Z, and developer Bruce Ratner ”fraudulently conspired” to use “loopholes” in the U.S. Patent Office so that they could use the name he registered.

He also claims that he spoke with officials at the NBA and at the New Jersey Nets before the team moved to Brooklyn, who assured him that the team would most likely opt for ‘New York Nets’ if they moved.

De Cassagnol has been embroiled in the dispute since 2012, however, and a previous appeal to the Patent Office found in favour of the NBA, judging that his uses of the Brooklyn Nets names weren’t significant enough to overrule the NBA’s trademark application.

Jay Z was forced to sell his shares in the team last year after opening his own sports agency firm, but he still owns part of the Nets’ home, the Barclays Center.

Anyway, it’s onto the next one for Jay – he’s reportedly in talks with DJ Calvin Harris and Trainspotting author Irvine Welsh to develop an HBO comedy set in “the world of electronic music”. This Sunday (January 26) he’ll perform alongside Beyoncé at the Grammy Awards.