The United States Department of Justice's Office of Special Investigations (OSI) was established in 1979 for the purpose of investigating and bringing suit to denaturalize and deport persons who took part in Nazi-sponsored acts of persecution, and to exclude from entry into the United States any person listed on OSI's "watch list" of suspected Nazi and Axis persecutors. Since its inception through 2004, OSI has denaturalized 98 individuals and brought action against an additional 34 suspected persecutors; it has also assembled a list of nearly 70,000 foreign individuals whose names it added to the United States Government's "watchlist" to be denied entry into the country. The targets of OSI's activities are largely Americans who entered the United States under false pretenses by hiding their Nazi past when applying for residency or citizenship; many have been deported. Since 2004, OSI's mandate has been expanded, and the agency is now also responsible for investigating and taking legal action to denaturalize American citizens who took part in war crimes, crimes against humanity, genocide, or torture outside of the United States.
OSI has handled several high-profile cases, including placing former Austrian President and United Nations Secretary General Kurt Waldheim on the "watch list," based on Waldheim's service in the Wehrmacht while in the Balkans and Greece as Jews were being deported and murdered there. OSI also successfully prosecuted Arthur Rudolph, the former project director of NASA's Saturn V moon rocket program, who left the country in 1984 when OSI proved he served from 1943 to 1945 as director of the Mittelwerk slave labor V-2 rocket factory. In 1981, Karl Linnas was stripped of his citizenship when OSI shed light on his notorious past as commander of the Tartu, Estonia, concentration camp and his personal involvement in the killing of thousands of Jews.
One case in which OSI found itself enmeshed in controversy was that of John Demjanjuk, a retired Cleveland, Ohio, auto worker. In news that attracted international headlines, the Justice Department accused Demjanjuk of being "Ivan the Terrible," an infamous and brutal Ukrainian guard at Treblinka. In 1982, Demjanjuk was stripped of American citizenship and deported by OSI to Israel, where he was convicted of murder, though his conviction was overturned by the Israeli Supreme Court in 1993 for lack of evidence. The United States Court of Appeals for the Sixth Circuit subsequently ruled that OSI had "acted with a reckless disregard for the truth" in the case. Nonetheless, in a separate legal case brought by OSI, Demjanjuk was eventually stripped of his citizenship for his activities in the Sobibor death camp and several concentration camps.
The directors of the OSI have included Walter Rockler (1979–80), a former Nuremberg prosecutor, Allan A. Ryan, Jr. (1980–83), Neal M. Sher (1983–94), and Eli M. Rosenbaum (1994– ).