Fox News reacted with outrage Monday to the revelation that the Justice Department tried to criminalize the newsgathering activities of reporter James Rosen in 2009 “for simply doing his job.”

“It is downright chilling,” Michael Clemente, executive vice president for news, said in a statement. “We will unequivocally defend his right to operate as a member of what up until now has always been a free press.”

The reaction from Fox came after the Post reported Monday on the Justice Department’s investigation into a possible leak of classified information about North Korea. A former State Department arms expert, Stephen J. Kim, was charged in 2010 with illegally disclosing national defense information to Rosen, Fox’s chief Washington correspondent.

Federal investigators seeking Rosen’s personal e-mail suggested in a 2010 search warrant that he was potentially criminally liable for soliciting the disclosure of classified information. The warrant was unsealed in 2011, but a Fox executive confirmed that the network was not aware of the allegations until Reading the Post’s report Monday.

No reporter, including Rosen, has ever been prosecuted for soliciting such information. But media lawyers and government transparency experts said that the Justice Department’s characterization of Rosen as a possible co-conspirator had crossed a line.

“Asking for information has never been deemed a crime,” said Steven Aftergood, the director of the Project on Government Secrecy at the Federation of American Scientists. “It’s a line that has not been crossed up until now.”