The former San Francisco 49ers quarterback, who has been a free agent since opting out of his contract in March, argues that the owners conspired to keep him out of the league.

According to ESPN, Kaepernick has chosen to hire attorney Mark Geragos instead of going through the NFL Players’ Association. Geragos has represented a number of well-known clients, from Bill Clinton’s brother Roger Clinton, pop star Michael Jackson, former NASCAR driver Jeremy Mayfield and musician Chris Brown.

The move is likely to exacerbate an already fragile situation, in which the league has showed public support for players’ right to protest, while trying to keep onside those who believe such demonstrations display a lack of patriotism. The accusations–including an array of comments from President Donald Trump–has prompted a number of experts and players to argue that Kaepernick’s activism is the main reason he’s been unable to sign with another team this season, and that all 32 teams in the NFL have colluded to ensure this.

Read: NFL Commissioner Roger Goodell Calls for an End to the National Anthem Controversy

Trump, who has called for protesting players to be benched by their owners, has taunted the NFL over falling ratings for this year’s games, which he has taken as evidence of public disgust at the protests. An open letter from NFL Commissioner Roger Goodell to team owners last week, in which he urged teams to end the dispute as soon as possible, hinted heavily at how it had put significant commercial pressure on the league.

ESPN said the filing demands an arbitration hearing around the matter, asserting the NFL and its owners “have colluded to deprive Mr. Kaepernick of employment rights in retaliation for Mr. Kaepernick’s leadership and advocacy for equality and social justice and his bringing awareness to peculiar institutions still undermining racial equality in the United States.”