It was just four years ago that roughly two dozen representatives of major news organizations crowded around a conference table at the Justice Department for a meeting with Attorney General Eric H. Holder Jr. Our agenda? Strengthening the Justice Department's guidelines that limit when federal prosecutors can serve subpoenas on the news media. It had just been revealed that federal investigators had secretly seized the phone records of The Associated Press and the emails of a Fox News correspondent during leak investigations. The result was important: The Justice Department revised its internal guidelines to make it harder for prosecutors to obtain subpoenas for reporters' testimony and records. Attorney General Jeff Sessions, after being chided by President Trump for being weak, recently declared a war on leakers and made clear that the news media was also on his mind. It seems all but certain that the Justice Department will try to chip away at the subpoena guidelines, [which] say that prosecutors are to seek testimony and evidence from journalists only as a last resort, and that news organizations should have a chance to go to court to challenge any subpoenas. The guidelines are far from ironclad. If a prosecutor were to ignore them, a journalist would have no right to go into court and demand they be followed. When federal courts dial back protection for reporters, the guidelines become an essential first line of defense against overzealous prosecutors.