SEATTLE (AP) — In another struggle over protest symbols in the workplace, employees at Seattle-area QFC and Fred Meyer stores are saying a ban on “Black Lives Matter” buttons violates federal labor law and their union contract.

Motoko Kusanagi works at the QFC in Seattle’s University Village and told The Seattle Times the store’s director has been asking employees to take the pin off.

On Tuesday, United Food and Commercial Workers Local 21 filed an unfair labor charge with the Labor Relations Board against QFC and Fred Meyer, both owned by Seattle-based supermarket giant Kroger.