The right of workers in private employment to form unions and bargain collectively with their employers is guaranteed by the National Labor Relations Act (NLRA) and related federal laws. The NLRA is preemptive, meaning that it supersedes state law in the areas that it covers. For example, the Illinois Appellate Court upheld the dismissal of a union's breach of labor contract claim against an employer, because it was preempted by the NLRA (Missouri Portland Cement Co. v. United Cement, Lime, Gypsum, & Allied Workers International Union, 506 N.E.2d 620 Ill. App. 1987)). However, in areas not covered by the NLRA, such as the rights of public employees and the rights of private employees who are not engaged in interstate commerce, the states are free to make their own provisions. Additional information on Illinois law in areas not covered by the NLRA is available.