Colin Kaepernick has filed a lawsuit against NFL owners over what he alleges is collusion not to sign him.
The 29-year-old has been without a team since he opted out of his contract with the San Francisco 49ers in March.
Kaepernick is credited with starting a protest against racial injustice, taken up by many other NFL players and athletes from other sports. He first protested by sitting during the national anthem in August 2016, before opting to kneel instead.
The protest has drew condemnation from some, most notably President Trump, who said that those who do not stand for the anthem should be fired.