Carnovsky was at one time a member of the American Communist Party. In April 1951, when questioned by the House Un-American Activities Committee (HUAC), he refused to answer any questions, citing his rights under the U.S. Constitution. At the same hearing, actor Marc Lawrence testified that he and Carnovsky had attended some of the same Communist Party functions. Carnovsky issued a statement after the hearing which said the committee's work was not really an inquiry, but "an inquisition into the inviolable area's of one's deepest manhood and integrity–the end result is the blacklist, the deprivation by innuendo of one's right to life, liberty and the pursuit of happiness in work."