This year completes exactly a half century in the federalization and codification of American labor law. Before that the regulation of both the internal affairs and external relations of labor organizations was left largely to the individual states, usually through the application of common or nonstatutory law by the courts. One major exception was the railroad industry, whose patent importance to interstate commerce made it an acceptable subject for federal legislation like the Railway Labor Act.
St. Antoine, Theodore J. "The Regulation of Labor Unions." Am. J. Comp. L. 30, suppl. (1982): 299-314.