Which act amended the NLRA to redefine unfair labor practices to include actions by unions as well as management?

The Taft-Hartley Act of 1947 is the correct answer because it specifically introduced changes to the National Labor Relations Act (NLRA), expanding the definition of unfair labor practices to include prohibitive actions not only by employers but also by labor unions. This piece of legislation was a response to concerns about the potential overreach of union powers and aimed to create a more balanced approach in labor relations.

The Taft-Hartley Act made significant amendments to the NLRA, introducing provisions that restricted union activities, including secondary boycotts, jurisdictional strikes, and union shops, among others. This reflected a shift in the regulatory landscape of labor relations, highlighting a growing concern for the rights of employees and employers alike.

In contrast, the Wagner Act, or the National Labor Relations Act of 1935, originally established the rights of workers to organize and engage in collective bargaining but did not address union actions as unfair labor practices. The Railway Labor Act primarily governs labor relations in the railroad and airline industries, having a different focus than the NLRA. As such, the Taft-Hartley Act represents a significant legislative milestone in broader labor relations by including unions in the definition of unfair practices.