The National Basketball Referee’s Association has filed charges with the National Labor Relations Board contending that the NBA has violated federal laws by engaging in unfair labor practices.

The charges revolve around what the referees' union describes as “the league’s refusal to negotiate with the union concerning non-economic issues.”

The league’s collective bargaining agreement with its referees expires Sept. 1.

The union has met three times with the NBA, most recently on March 31.  It contends that the NBA hasn’t responded to any of its proposals.