Back in 1989, Rocky Flats was the center of all the attention because its plant was allegedly not following federal regulations on health, environmental and safety standards. After a whistleblower went to the EPA, one branch of the U.S government (the EPA) decided to look into another (DOE).
Since the EPA is mostly a regulatory body, it needs the help of the FBI to investigate the matter further. One way to check the whistleblowers' account was to enter the facility. The FBI (Justice Department ) and the EPA then decided to set up joint task force and a raid was decided. Now, one needs to realize that entering a federal facility is one thing if you're an agency of the government, but it is somewhat a totally different thing if you're an agency of the government and want to enter a facility where nuclear weapons are built. It's a federal facility all right, but of a special kind.
In to make the raid happen, the Secretary of Justice at the time asks the Undersecretary of Energy to come by their offices because "they need to talk". Once in the room, the undersecretary is surrounded by Justice department officials and abruptly learns that one of his facility is going to be raided by 150 agents the morning after. This is first time this has ever happened in the history of the Department of Energy (or the Atomic energy commission) in that one branch of the government is going to be raiding another branch of the government. This is stunner for him but he is also sworn to secrecy because nobody wants any leaks to reach the Rocky flats folks. After much dismay that one arm of the government would do that to another, the Department of Energy official inquires on how they are going to raid *that* facility. The following is an account of that discussion:
Justice Dept Rep: Well we have about 150 agents ready to show up tomorrow morning at 7:00, we'll say who we are, show our credentials and be on our merry way
DOE Rep: But surely you realize that these guys are a little army on their own, they train on scenarios like this where the bad guys say they work for the FBI/CIA and whatnot. I mean these people will not just not let you in, whoever the hell you think you are
JD Rep: But we're the FBI!
DOE Rep: How are they going to know you're the FBI ?
....
After a long discussion, the facility was eventually raided the day after....