I would say that the Pentagon Papers case of 1971 - in which the government tried to block the The New York Times and The Washington Post that they obtained from a secret study of how we got involved in the war in Vietnam - that is probably the most important case.
“We don't know all the answers. If we knew all the answers we'd be bored, wouldn't we? We keep looking, searching, trying to get more knowledge.”
“So long as there are earnest believers in the world, they will always wish to punish opinions, even if their judgment tells them it is unwise and their conscience that it is wrong.”