North Carolina Speaker Ban

On June 26, 1963, the North Carolina General Assembly passed the Act to Regulate Visiting Speakers, later known as the Speaker Ban Law. The law forbade anyone to speak on a University of North Carolina campus who was a known member of the Communist Party, or who was known to advocate overthrow of the United States Constitution, or who had invoked the Fifth Amendment in respect of communist or "subversive" connections.

Source: Wikipedia — North Carolina Speaker Ban (CC BY-SA 4.0)