The NFL Players' Association is preparing to mount a challenge to the league's new national anthem policy.
The NFLPA is seeking options to challenge the legality of the policy by retaining multiple law firms, Pro Football Talk reported Thursday, citing a source with knowledge of the situation.
NFL owners unanimously approved a new policy on May 23 that requires players and league personnel on the sidelines to stand for the national anthem but gives them the option to remain in the locker room if they desire.
The policy subjects teams to a fine if a player or any other personnel do not show respect for the anthem. Those clubs will also have the option to fine any team personnel for the infraction.
The NFLPA immediately objected to the policy upon the announcement, arguing in a statement that "the NFL chose to not consult the union in the development of this new 'policy.'"
The union warned at the time that it would "review the new 'policy' and challenge any aspect of it that is inconsistent with the collective bargaining agreement."
The story by Pro Football Talk mentioned that one legal challenge could come in the form of a "non-injury grievance" under the agreement.
The anthem issue has been a divisive one, with some feeling players not standing for the song is disrespectful to, among others, the U.S. military. Others feel it is the players' right to protest perceived social injustice peacefully.
The change in policy comes after some players elected against standing for the national anthem.
Earlier this month, President Donald Trump rescinded an invitation for the Super Bowl champion Philadelphia Eagles to visit the White House after learning that only a handful of players planned to attend.
Former San Francisco 49ers quarterback Colin Kaepernick started the movement in 2016 to kneel during the national anthem as a protest to denounce police brutality against African-Americans, social injustice and racial inequality.
Kaepernick and former 49ers safety Eric Reid have filed collusion cases against the league after failing to land jobs as free agents.
The anthem topic became a central issue for the NFL after Trump criticized the movement during a speech last September, stating players should be fired for not standing.