During World War II, he applied for admission and was admitted into the United States as a Mexican alien railroad worker. His application for such entry contained his recitation that he was a native-born citizen of Mexico. By 1947, however, Perez had returned to Mexico, and in that year, he applied for admission to the United States as a citizen of the United States. Upon his arrival, he was charged with failing to register under the Selective Service Laws of the United States during the war.