In October 1947, Peters was served with an arrest warrant for alleged violation of the Immigration Act of 1924, which required alien immigrants in America to possess a valid visa. On August 3, 1948, while appearing under subpoena before the House Committee on Un-American Activities (HUAC), Whittaker Chambers identified Peters as a spy. Later that month, Peters appeared under subpoena before HUAC but did not cooperate. He invoked the Fifth Amendment and refused to answer sensitive questions. On May 8, 1949, Peters left for communist Hungary to avoid imminent deportation by the U.S. Immigration and Naturalization Service. Peters adopted the name "József Péter" and remained in Hungary until his death in 1990.