What is Labor Management Relations Act Of 1947?

Legal Definition
The Labor Management Relations Act of 1947 29 U.S.C. § 401-531 better known as the Taft–Hartley Act, (80 H.R. 3020, Pub.L. 80–101, 61 Stat. 136, enacted June 23, 1947) is a United States federal law that restricts the activities and power of labor unions. The act, still effective, was sponsored by Senator Robert A. Taft and Representative Fred A. Hartley, Jr., and became law by overcoming U.S. President Harry S. Truman's veto on June 23, 1947; labor leaders called it the "slave-labor bill" while President Truman argued that it was a "dangerous intrusion on free speech," and that it would "conflict with important principles of our democratic society." Nevertheless, Truman would subsequently use it twelve times during his presidency. The Taft–Hartley Act amended the National Labor Relations Act (NLRA; informally the Wagner Act), which Congress passed in 1935. The principal author of the Taft–Hartley Act was J. Mack Swigert, of the Cincinnati law firm Taft, Stettinius & Hollister.

Historian James T. Patterson concludes that:

By the 1950s most observers agreed that Taft-Hartley was no more disastrous for workers than the Wagner Act had been for employers. What ordinarily mattered most in labor relations was not government laws such as Taft-Hartley, but the relative power of unions and management in the economic marketplace. Where unions were strong they usually managed all right; when they were weak, new laws did them little additional harm.
-- Wikipedia