In an official grievance filed Sunday against the NFL, Colin Kaepernick alleges he remains out of the league due to team owners punishing him for kneeling during the national anthem.

The former 49ers quarterback became a free agent in March. No team has given him a shot.

Mark Geragos, one of Kapernick’s attorneys, released an official statement about the grievance on Twitter. The statement reads, in part:

If the NFL (as well as all professional sports leagues) is to remain a meritocracy, then principled and peaceful political protest — which the owners themselves made great theater imitating weeks ago — should not be punished and athletes should not be denied employment based on partisan political provocation by the executive branch of our government. Such a precedent threatens all patriotic Americans and harkens back to our darkest days as a nation. Protecting all athletes from such collusive conduct is what compelled Mr. Kaepernick to file his grievance.

During the 2016 preseason, Kaepernick began peacefully demonstrating during the anthem to protest police brutality, namely the police shooting deaths of unarmed African-Americans.

As of October 6, NFL teams had signed 64 quarterbacks – none of them Kaepernick and most of them painfully mediocre.

The timing of Kaepernick’s grievance may force owners to explicitly address this at the annual fall meetings which start Tuesday.

ESPN NFL reporter Jim Trotter says Kaepernick faces an uphill battle.

“Winning a collusion suit is extremely difficult,” Trotter said on ESPN’s air Sunday. “He would have to prove that 32 owners got together and said ‘We are not going to sign this guy.’ And I’ve talked to multiple owners who have all said that they have never had that conversation with another one of their colleagues.”

Read the full grievance here.

Kaepernick’s goal is to be “treated fairly by the league” and “return to the football playing field,” according to Geragos statement.