P is a Minnesota-incorporated membership organization consisting of more than 1,250 Minnesota employers. P provides labor relations specialists who assist over 200 of its members in the collective bargaining process throughout Minnesota. Steelworkers (D) is a labor organization. D is the exclusive bargaining representative of, and has bargained for, a number of P's members' employees. The State of Minnesota has intervened in this action to defend the constitutionality of the Striker Replacement Law. The Striker Replacement Law provides: It is an unfair labor practice for an employer . . . (9) To grant or offer to grant the status of permanent replacement employee to a person for performing bargaining unit work for an employer during a lockout of employees in a labor organization or during a strike of employees in a labor organization authorized by a representative of employees . . . . If an employer hires or threatens to hire permanent replacement workers, a union may seek a temporary or permanent injunction in state court to enjoin the unfair labor practice. P seeks a declaratory judgment that the Striker Replacement Law is preempted by federal labor law.