Former San Francisco quarterback Colin Kaepernick, who sparked backlash by starting the trend of NFL players kneeling during the national anthem, has filed a grievance accusing NFL owners of colluding against him under the latest collective bargaining agreement, according to a report out Sunday.

Bleacher Report’s Mike Freeman said in a series of tweets that the controversial athlete has hired attorney Mark Geragos “who has represented numerous high profile clients.”

Geragos said in a statement posted on Twitter on Sunday that he filed the grievance “only after pursuing every possible avenue with all NFL teams and their executives.”

“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,” Geragos said in the statement, “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.”

Kaepernick threw for 2,241 yards, 16 touchdowns and four interceptions during the 2016 season. However, since becoming a free agent, Kaepernick has had difficulty finding a job over the league-wide demonstrations during the national anthem that protest social injustice.

Commissioner Roger Goodell, according to Bleacher Report, has denied any blackballing of Kaepernick.

“I believe that if a football team feels that Colin Kaepernick, or any other player, is going to improve that team, they’re going to do it,” he said in June to ESPN.com.

The NFL players’ union said it would support the grievance, which was filed through the arbitration system that’s part of the league’s collective bargaining agreement.

According to Fox 13 Memphis, Kaepernick may have a good case as there have been owners, such as John Mara of the New York Giants, who have publicly said that they would not hire him and the Denver Broncos reportedly would not pursue him under any circumstances.

President Donald Trump began feuding with the NFL in September after asking at a political rally in Alabama: “Wouldn’t you love to see one of these NFL owners, when somebody disrespects our flag, to say, ‘Get that son of a b---- off the field right now, out. He’s fired. He’s fired!’”

Trump told Fox News’ Sean Hannity Wednesday that the NFL should have suspended Kaepernick for kneeling during the playing of “The Star-Spangled Banner.”

“The NFL should have suspended him for one game and he would have never done it again,” Trump told host Sean Hannity in Harrisburg, Pa. “They could have then suspended him for two games and they could have suspended him again if he did it a third time, for the season, and you would never have had a problem.”

“I will tell you,” Trump told Hannity, “you cannot disrespect our country, our flag, our anthem, you cannot do that.”

The Associated Press contributed to this report.