Removing these items from the potential means of forfeiting U.S. nationality, the Nationality Act retained as possible causes of denaturalization, treason, sedition, or conspiring against the United States; employment as an official with policy-making authority of a foreign government; and voluntary renunciation. Fraud, committed in conjunction with an application for naturalization can also make nationality voidable. Typically, prominent former Nazi officers who acquired U.S. nationality have had it revoked if the Office of Special Investigations has been able to prove that the naturalization was obtained by concealing their involvement in war crimes committed during World War II. They cannot be tried for crimes committed elsewhere, thus are denaturalized for immigration violations, and once they become aliens, ordered deported.