One for the Supremes
Branzburg itself held that "news gathering is not without its First Amendment protections, and grand jury investigations if instituted or conducted other than in good faith, would pose wholly different issues for resolution under the First Amendment." And Justice Powell's concurrence held that a claim to privilege "should be judged on its facts by the striking of a proper balance between freedom of the press and the obligation of all citizens to give relevant testimony with respect to criminal conduct."
So it's clear, even from Branzburg, that there are some areas where the first amendment does give some protection to reporters' revealing of sources.
Moreover, the Branzburg holding has been "chipped away at." The cases since Branzburg have held that there is a balancing test, where courts are required to "look to the facts on a case-by-case basis in the course of weighing the need for the testimony in question against the claims of the newsman that the public's right to know is impaired." Carey v. Hume (DC Cir. 1972), cited in Judge Tatel's concurring opinion. Judge Tatel's concurrence cites numerous circuits that have held the same, that there is qualified first amendment protection for reporters' sources.
I think this is one the Court should take. Either Judge Sentelle is right and the majority of the circuits are not taking Branzburg seriously enough, or (more likely) Branzburg should be should be limited. As much as I don't want more ammo for the Bush-haters, I don't think, as Lord Coke does, that this is an instance of the "crusade to pigeonhole every conceivable human interest into various protections of the Bill of Rights." The right to keep reporters' sources confidential is not a huge right without any textual support, but is protecting something at the core of democratic government.