Nearly all rank-and-file employees in private businesses of any substantial size in the United States are protected by federal law against antiunion discrimination. The Railway Labor Act applies to the railroad and airline industries. The National Labor Relations Act (NLRA) applies to all other businesses whose operations "affect [interstate] commerce" in almost any way. Supervisory and managerial personnel, domestic servants, and agricultural workers are excluded from this federal scheme. Separate federal law covers the employees of the federal government. About thirty of the fifty states have statutes ensuring the right to organize on the part of some or most of the state and municipal employees. This paper will concentrate on the NLRA, by far the most significant legislation dealing with private sector employees.
St. Antoine, Theodore J. "Prevention of Antiunion Discrimination in the United States." Comp. Lab. L. J. 9 (1988): 384-98.