Day to day, it's something journalists in America are having to do, whether they're aware of it or not. The politician in question is Attorney General Eric Holder, and the key quote in question is his vow to Congress:
As long as I'm attorney general, [the DoJ] will not prosecute any reporter for doing his or her job.
That memo doesn't quite seem to have filtered down to federal agencies, if a recent report to Slate is to be believed. Ryan Gallagher, one of the site's security writers, has produced a long account of the strange tale of Sigurdur Thordarson, who became a WikiLeaks insider at just 17 years old, who then proceeded to voluntarily turn FBI informant.
The investigation into WikiLeaks has prompted little concern among mainstream US journalists. This might be because WikiLeaks doesn't produce the same style of journalism, or because reporters can reassure themselves, rightly or wrongly, that the investigation centers on trying to uncover any inappropriate dealings with sources, or involvement in hacking.