Taft–Hartley Act

The Labor Management Relations Act of 1947 is a United States federal law that restricts the activities and power of labor unions. 
The act, still active, was sponsored by Senator Robert A. Taft and Representative Fred A. Hartley, Jr., and became law despite 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", arguing that it would "conflict with important principles of our democratic society". 
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 &amp; Hollister.