The Labor Management Relations Act of 1947 better known as the Taft–Hartley Act, (80 H.R. 3020, ) 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”.Harry S. Truman: Veto of the Taft-Hartley Labor Bill 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.