Branzburg v. Hayes, the split U.S. Supreme Court decision (1972) generally construed by journalists and judges alike as affirming some sort of reporter's privilege in federal courts.
U.S. Appellate Judge Richard Posner's influential opinion in
McKevitt v. Pallasch (2003) telling those journalists and judges they were wrong -- there is no such privilege.
John Milton's
Areopagitica (1643), one of the earliest and most eloquent arguments for a free press. Said Milton: "As good almost kill a man as kill a good book; who kills a man kills a reasonable creature, God's image; but he who destroys a good book, kills reason itself, kills the image of God, as it were in the eye."