Aliens — Refugees — Admission — Displaced persons — Criteria governing granting of entry visas to displaced persons — Persons assisting “the enemy” in persecuting civilian populations” ineligible for grant of entry visa — Failure of displaced person to disclose prior involuntary service as concentration camp guard — Whether invalidating entry visa and thereby rendering him subject to denaturalization — Displaced Persons Act 1948 — Immigration and Nationality Act 1952 — The law of the United States