A Justice Department demand for the return of a classified document sent to the American Civil Liberties Union is triggering a First Amendment battle that could have wide-ranging implications for journalists and others who track national security matters.

The ACLU disclosed yesterday that it is fighting a federal grand jury subpoena that seeks “any and all copies” of a 3 1/2 page document, marked “secret,” that was sent by e-mail to the group in October by a source whom ACLU officials declined to identify.

“This is the first time in our knowledge in the ACLU’s 86-year history that we’ve been asked to make a document disappear from our files,” the group’s executive director, Anthony Romero, told reporters yesterday. “We resist such an effort as a matter of principle and as a matter of right.”

On Monday, the ACLU moved to quash the subpoena, which was issued on November 20. Judge Jed Rakoff has put aspects of the dispute under seal, but the civil liberties group said he agreed yesterday to make the subpoena and some of the legal filings public.

Mr. Romero said the government is abusing the grand jury process because prosecutors have no legitimate need for the document, and particularly not for any extra copies the ACLU may have. “The government knows quite well what we have and the government knows the source that provided it to us,” he said.

Mr. Romero said that if a grand jury subpoena can be used to seize all copies of classified documents, journalists could be prevented from reporting on critical national issues. “If the government had done so with the Pentagon Papers and had served a grand jury subpoena to the New York Times and the Washington Post, it would have been no different than having a prior restraint,” he said. A lawyer at the U.S. attorney’s office in Manhattan, Cathy Seibel, said she could not discuss the matter due to grand jury secrecy rules and court orders.

The subpoena indicates that the grand jury is investigating a violation of a federal law regarding the handling of defense-related information, the Espionage Act of 1917. Mr. Romero said his group had been assured that it is not the target of the probe. However, he said the inquiry “raises some of the same questions” posed by the ongoing prosecution under the Espionage Act of two former lobbyists for the American Israel Public Affairs Committee. Those lobbyists, Steven Rosen and Keith Weissman, have argued, largely without success, that the law is overbroad and should only prohibit improper disclosures by government officials. Mr. Romero described the disputed document as “mildly embarrassing” to the government, but he said it was far from Earth-shattering. “There’s very little in the document that is remarkable or especially newsworthy,” he said, declining to explain further.

The subpoena describes the record in question as an “information paper” dated December 20, 2005. The term, “information paper,” is used regularly by the Pentagon. The ACLU Web site includes several such documents produced in response to a Freedom of Information Act lawsuit the group filed seeking records about allegations of detainee abuse in Iraq and at Guantanamo Bay. Mr. Romero confirmed that the document relates to the group’s advocacy, but he would not elaborate.

“Certainly, if a newsroom got this sort of subpoena for every single copy of something, you can bet the media would raise all sorts of hell,” the executive director of the Reporters Committee for Freedom of the Press, Lucy Dalglish, said. Journalists have some additional protection from such subpoenas under federal laws and Justice Department regulations, but might wind up with the same constitutional arguments the ACLU is likely to raise, she said.

A former prosecutor, Andrew McCarthy, said the government was being respectful of the ACLU’s privacy to a degree by relying on a subpoena rather than a search warrant. “This seems to be the least intrusive way,” he said.

Mr. McCarthy said that as long as the document involves a real national security secret and not merely something embarrassing, prosecutors were well within their rights in issuing the subpoena. “There’s a lot of law saying the grand jury is entitled to every man’s evidence,” he said.