The NFL players union filed a grievance Monday on behalf of former 49ers safety Eric Reid, perhaps the most prominent player who protested during the national anthem last season and who remains jobless nearly two months after free agency began.
The NFL Players Association says that an NFL team appears "to have based its decision not to sign a player based on the player's statement that he would challenge the implementation of a club's policy prohibiting demonstration."
The NFL does not have a policy prohibiting players from protesting during the anthem and has said it will respect players' right to do so.
Reid and other players knelt during the pre-game anthem last season. Reid has said he does not plan to kneel in 2018.
The union also says "at least one club owner has asked pre-employment interview questions about a player's intent to demonstrate. We believe these questions are improper, given league policy."
The grievance appears to be related to a Pro Football Talk report about Reid's free-agent visit with the Cincinnati Bengals and team owner Mike Brown.
The 49ers, meanwhile, have said they would consider re-signing Reid. However, it likely would be as a backup safety, while Reid, a former first-round draft pick, is looking for a starting job and a long-term contract.