The Walter-McCarren Act goes into effect, changing some of the criteria for immigrants to be admitted to the U.S. While it did little to change the quota system that was already in place, it still gave preference to European immigrants, specifically England, Ireland and Germany, giving these three countries two-thirds of the allocated slots available. But it did remove some racial barriers that had previously excluded Japan and China, which were assigned very small quotas.
The Act called for a more intense screening to make sure anyone labeled a subversive was not allowed entry and those from communist or communist-front organization were to be deported. “In defending the act, Senator McCarren declared, "If this oasis of the world should be overrun, perverted, contaminated, or destroyed, then the last flickering light of humanity will be extinguished."
President Harry S. Truman took a very different view, calling the legislation "un-American" and inhumane. When the bill was passed in June 1952, Truman vetoed the bill. Congress overrode his veto, and the act took effect in December.”