Undercover and Sensitive Operations Unit Attorney General's Guidelines on FBI Undercover Operations Revised 11/13/92 [open pdf - 55KB]
"The following Guidelines on the use of undercover activities and operations by the Federal Bureau of Investigation (FBI) are issued under the authority of the Attorney General provided in Title 28, United States Code, Sections 509, 510, and 533. They apply to all investigations conducted by the FBI, except those conducted pursuant to its foreign counterintelligence and foreign intelligence responsibilities. The use of the undercover technique, including proprietary business entities, is essential to the detection, prevention, and prosecution of white collar crimes, public corruption, terrorism, organized crime, offenses involving controlled substances, and other priority areas of investigation. However, these techniques inherently involve an element of deception and may require cooperation with persons whose motivation and conduct are open to question, and so should be carefully considered and monitored."
United States Department of Justice: http://www.usdoj.gov/