Federal Bureau of Investigation

The Federal Bureau of Investigation, also known as the FBI, was the primary law enforcement agency of the Federal government of the United States of America on Earth. The FBI was established in the first part of the 20th century, and remained active well into the 21st century.

After a time traveling Pavel Chekov was captured on board the USS Enterprise (CVN-65), he was interrogated by an FBI agent. After hearing Chekov's responses to his questions, he believed that while Chekov was a Russian, he was also mentally impaired. (Novelization of Star Trek IV: The Voyage Home)