The U.S. Federal Bureau of Investigation has threatened Wikipedia with legal action if the online encyclopedia doesn't remove the FBI's seal from its site.

The seal is featured in an encyclopedia entry about the FBI.

Wikipedia isn't backing down, however. The online encyclopedia -- which is run by a nonprofit group and is edited by the public -- sent a chiding letter to the FBI, explaining why, in its view, the FBI is off its legal rocker.

"In short, then, we are compelled as a matter of law and principle to deny your demand for removal of the FBI Seal from Wikipedia and Wikimedia Commons," the Wikimedia Foundation's general counsel, Mike Godwin, wrote in a letter to the FBI, which was posted online by the New York Times.

"We are in contact with outside counsel in this matter, (Seal Online Cegel)and we are prepared to argue our view in court."

The whimsically written letter from Wikipedia says the FBI's reading of relevant law is both "idiosyncratic" and "more importantly, incorrect." It also notes that the FBI's seal appears on other websites, including in an online entry from Encyclopedia Britannica.

In a letter dated July 22, and also posted online by the Times, the FBI told Wikipedia it must remove the bureau's seal because the FBI had not approved use of the image.

"The FBI has not authorized use of the FBI seal on Wikipedia," the letter says. "The inclusion of a high quality graphic of the FBI seal on Wikipedia is particularly problematic, because it facilitates both deliberate and unwitting" copying and reprinting of the seal's image.

The FBI's deputy general counsel, David Larson, cities a particular law that says duplicating an official "insignia" is illegal without permission.

But Wikipedia strikes back on that point, saying the FBI redacted the most important part of that U.S. code, which defines an insignia as "any badge, identification card, or other insignia."