Apparently, reporters can write their stories based on information from those they promise not to identify and there is nothing that can be done. What is there to keep reporters from fabricating, say, a 30 year-old military memo? They set it up in Microsoft Word and then the "age" it on a photocopier. Then they can keep secret the fact that they invented the story and the proof by stating that the information was given to them by a confidential informant.
Of course we know such a scenario is not likely (wink) but why leave open the option to cheat?