On this date in 1947
The Taft-Hartley Act (officially the Labor Management Relations Act of 1947), passed over President Trumans veto on this day and was the first major labor relations law since the Wagner Act (signed July 5, 1935).
Organized labor bitterly opposed the law, denouncing it as the slave-labor bill. The new Republican majorities in both houses of Congress (as a result of the 1946 mid-term elections), however, were able to pass it over his veto.
The most offensive civil liberties aspect of the law was a loyalty oath provision for union leaders, which required them to file affidavits with the Department of Labor stating that they were not members of the Communist Party or other organization advocating the violent overthrow of the government. The Supreme Court in American Communications Association v. Douds (1950) ruled that the loyalty oath did not violate the First amendment.
The loyalty oath in the new law was another manifestation of the mania for loyalty oaths during the Cold War. See, for example, the University of California loyalty oath adopted in April 21, 1950; the loyalty oath for residents of federally-assisted public housing on July 5, 1952; the loyalty oath for federal student aid in the National Defense Education Act (September 2, 1958); and the loyalty oath for Medicare recipients (February 13, 1967), which never went into effect.
The Taft-Hartley Act also had a provision that allowed the president of the U.S. to intervene in possible strikes and to impose a cooling off period. This provision effectively limited unions right to strike. Finally, the law allowed employers to deliver anti-union messages at the work place (but not outside the workplace), a practice that had previously been barred under an interpretation of the Wagner Act.
Learn about the origins of the Taft-Hartley Act:
http://hnn.us/article/1036
Read: Robert W Cherny, William Issel, and Kieran Walsh Taylor, American Labor and the Cold War: Grassroots Politics and Postwar Political Culture (2004)
Learn more about the law:
http://www.nlrb.gov/who-we-are/our-history/1947-taft-hartley-substantive-provisions